San Luis Obispo City Council
June 16, 2026

2026 Water Supply and Demand Assessment
7 for Assessment Year supply availability projections. Based on those model runs, the combined safe annual yield for Salinas and Whale Rock reservoirs for the Assessment Year is estimated at 4,675 acrefeet, rather than the 4,910 acre-foot value referenced in the General Plan.

For the Assessment Year, the City assumes the following available supplies:
 Nacimiento Reservoir: 1,806 acre-feet, reflecting the temporary delivery limitations associated with pipeline damage from the 2023 storms;
 Salinas and Whale Rock Reservoirs: 4,675 acre-feet, based on Assessment Year model runs using the City’s safe annual yield model and accounting for the near-term effect of reservoir siltation;  Groundwater: 0 acre-feet, because groundwater is not assumed to be available for potable use during the Assessment Year;
 Recycled water: 1,296 acre-feet of non-potable supply available for use after accounting for required creek discharge obligations and infrastructure limitations.

Shortage Determination Methodology
For each month of the Assessment Year, projected water demand was compared against projected available supply. If projected available supply exceeded projected water demand, no shortage was identified for that month. If projected water demand exceeded projected available water supply, the shortage volume would be calculated as the difference between demand and supply, and the shortage percentage would be calculated as the shortage volume divided by unconstrained demand. Any identified shortage percentage would then be used to identify the applicable State standard shortage level and corresponding City WSCP stage.

In addition to the monthly supply and demand comparison, the City evaluates whether available water supplies are forecasted to last five years or longer under the input conditions used in the Water Projection Model. This longer-term availability assessment is important because the City’s WSCP is structured to guide shortage response actions when available supplies fall below the City’s established years-of-supply thresholds. Identifying a potential shortage multiple years in advance is a responsible water management practice because it provides time for the City to implement phased demand reduction measures, increase public outreach, adjust operations, preserve reservoir storage, evaluate supplemental supplies, and avoid more abrupt or disruptive restrictions later. Early identification also allows the City Council, staff, customers, and regional partners to respond in a measured and coordinated manner before shortage conditions become more severe. Accordingly, the Water Projection Model provides both an Assessment Year supply and demand comparison and an estimate of the number of years of available water supply remaining based on input conditions. The results of the monthly supply and demand comparison and the years-of-supply analysis are presented in Section V.

III. WATER SUPPLY SOURCE INFORMATION AND INFRASTRUCTURE

CONSTRAINTS
The City relies on multiple water supply sources to meet potable and non-potable demands. Potable supplies include surface water from Nacimiento Reservoir, Whale Rock Reservoir, and Salinas Reservoir.

Groundwater is being developed as a future supplemental potable supply but is not assumed to be available during the Assessment Year. Recycled water is used as a non-potable supply for approved uses,

2026 Water Supply and Demand Assessment
8 including landscape irrigation and construction-related uses, and offsets potable demand where recycled water service is available.

This section summarizes the City’s water supply sources and identifies infrastructure capabilities or plausible constraints that may affect Assessment Year availability. The source-specific assumptions described below inform the City’s Water Projection Model and are used to evaluate whether available supplies are sufficient to meet projected Assessment Year demands.

Nacimiento Reservoir
In 1959, the San Luis Obispo Flood Control and Watershed Protection District (San Luis Obispo District) entered into an agreement with Monterey County Flood Control and Water Conservation District (now Monterey County Water Resources Agency) to secure rights to 17,500 acre-feet of water per year (AFY) from Nacimiento Reservoir. Nacimiento Reservoir is located entirely within San Luis Obispo County, California (County), and was built by Monterey County Flood Control and Water Conservation District who continues to control reservoir ownership and operations. Nacimiento Reservoir has a storage capacity of 377,900 acre-feet and serves the purpose of abating seawater intrusion in the groundwater aquifers of the Salinas River Valley, while also providing flood protection and groundwater recharge for the Salinas Valley. Of the San Luis Obispo District’s entitlement, 1,750 AFY have been designated for uses around the lake, leaving 15,750 AFY for allocation to other areas within the County of San Luis Obispo.

Water is delivered via a 45-mile pipeline from Nacimiento Reservoir to participating agencies and cities.

The “dependable yield” from Nacimiento Reservoir is the contractual amount of water that the City has rights to from Nacimiento Reservoir. The City’s original contractual amount was 3,380 AFY. Engineering studies, environmental impact reports, dependable yield analyses, and preliminary design reports were completed to ensure water needs within the County were met. In 2004, the County solicited interested agencies who may be interested in participation in the Nacimiento Project. The four initial project participants included the cities of San Luis Obispo and Paso Robles, the Atascadero Mutual Water Company, and the Templeton Community Services District. These agencies executed participation agreements with San Luis Obispo County for entitlements of water which totaled 9,630 acre-feet. In 2004, the County Service Area 10A in Cayucos became a project participant securing 25 AFY. On June 29, 2004, the San Luis Obispo City Council authorized the City’s participation in the Nacimiento Water Project for the delivery of the original 3,380 AFY of water.

In March 2016, the City Council approved the addition of 2,102 AFY from Nacimiento Reservoir to the City’s water supply. This addition brought the City’s total Nacimiento Reservoir allocation to 5,482 AFY.

With uncertainty of future climatic conditions, regulation, and aging infrastructure at the City’s other surface water supplies, the additional supply of Nacimiento water to the City’s portfolio reduces pressure on the use of water supplies in the Whale Rock and Salinas reservoirs, extending these stored supplies during future critical water shortages.

During the worst-case drought on record in the region (2012 to 2014), Nacimiento Reservoir remained a resilient water supply capable of providing a consistent and reliable source of water for San Luis Obispo County. To confirm the prior analysis with more recent data, the City reviewed rainfall and inflow data from 2013 which was the driest year on record. Over that year, Nacimiento Reservoir received 35,000 acre-feet of inflow. Though this is significantly below the average inflow into the reservoir, the San Luis Obispo District’s entitlement could still be met if inflow remained at this level due to the District’s primary rights.

2026 Water Supply and Demand Assessment
9 Although Nacimiento Reservoir is considered a dependable long-term supply, a large storm event on January 9, 2023 exposed and damaged the pipeline that delivers water from Nacimiento Reservoir to the City, disrupting deliveries. In July 2025, the County of San Luis Obispo completed construction of a temporary bypass line that allows the City to receive up to 3.2 million gallons of Nacimiento water per day while awaiting completion of permanent pipeline repairs. County staff currently estimate that permanent repairs will restore the City’s full Nacimiento delivery capacity during fall/winter 2027.

For the Assessment Year, the City forecasts 1,806 acre-feet of available Nacimiento supply. This assumption reflects the temporary delivery limitation associated with the bypass connection and is lower than the City’s full 5,482 acre-foot annual entitlement. The temporary disruption in Nacimiento deliveries is accounted for on a monthly basis in the Water Projection Model, and reduced volumes are reflected throughout the Assessment Year, including no assumed Nacimiento deliveries in February or March 2027.

Whale Rock Reservoir
Whale Rock Reservoir is located on Old Creek Road approximately one-half mile east of the community of Cayucos, California. The project was planned, designed, and constructed under the supervision of the California State Department of Water Resources (DWR). Construction took place between October 1958 and April 1961. The reservoir is jointly owned by the City of San Luis Obispo, the California Men’s Colony, and California Polytechnic State University (Cal Poly). These three agencies form the Whale Rock Commission which is responsible for operation and administration of the reservoir and associated water deliveries. Day-to-day operation is provided by the City.

Whale Rock Reservoir is formed by an earthen dam and had the capacity to store an estimated 40,662 acre-feet of water at the time of construction; however, storage capacity has been slightly reduced and today’s capacity is estimated to be 38,967 acre-feet. The City owns 55.05 percent of the water storage rights at the reservoir (22,364 acre-feet). The remaining water storage rights are apportioned between the two State agencies with Cal Poly owning 33.71 percent and the California Men’s Colony owning 11.24 percent. Over the life of the Whale Rock Reservoir and dam, the lake has filled to capacity 14 times, most recently spilling in the spring of 2024.

The Whale Rock pipeline is approximately 17 miles long, connecting the reservoir to the member agencies, and terminating at the City's Water Treatment Plant. The design capacity of the pipeline is

18.94 cubic feet per second (approximately 8,500 gallons per minute). The line consists of modified prestressed concrete cylinder pipe at most locations. Whale Rock Reservoir and its associated conveyance systems are functioning as designed and the City is not aware of any issues that are anticipated to restrict delivery volumes in the Assessment Year.

Salinas Reservoir
The Salinas Reservoir (also known as Santa Margarita Lake) is located on the upper Salinas River, approximately nine miles southeast of the community of Santa Margarita. The project was originally built by the War Department to ensure an adequate water supply for Camp San Luis Obispo, as well as the City of San Luis Obispo. The dam and appurtenances were declared surplus by the War Department on April 14, 1947, and the U.S. Army Corps of Engineers assumed responsibility for the facilities. On July 11, 1947, the Corps entered into an agreement with the San Luis Obispo District for the operation and maintenance of the dam and related facilities. The City has an agreement with the Corps for use of the reservoir, as well as a water right permit to divert water from the Salinas River for storage within the reservoir. Immediately following construction, the reservoir had an estimated storage capacity of 24,000

2026 Water Supply and Demand Assessment
10 acre-feet with a surface area of 793 acres, and a drainage area of 112 square miles. In 2023, the District completed a bathymetric survey of the reservoir to update reservoir capacity calculations. The 2023 update resulted in a reduction of 1,522.56 acre-feet total capacity, reducing the overall capacity to 22,507.75 acre-feet. The decrease in capacity is attributed to siltation of the reservoir, which is estimated at 46.27 AFY (mean siltation rate over 33 years).

Water is conveyed from Salinas Reservoir through 48,700 feet (9.2 miles) of 24-inch diameter reinforced concrete pipe to a three-million-gallon forebay at the Santa Margarita booster pump station near the northerly base of Cuesta Grade adjacent to Highway 101. The pipeline is designed to flow by gravity from the Reservoir to the forebay when the lake level is above the elevation of 1,267 feet. A booster pump station at the base of the dam, consisting of two horizontal centrifugal pumps, is capable of maintaining the rated flow of 12.4 cubic feet per second (approximately 5,565 gallons per minute) when the water surface elevation falls below 1,267 feet. Salinas Reservoir and its associated conveyance systems are functioning as designed and the City is not aware of any issues that are anticipated to restrict delivery volumes in the Assessment Year.

Recycled Water
The City’s Water Resource Recovery Facility (WRRF) produces more than 4,000 acre-feet of disinfected tertiary-treated effluent each year. A minimum of 1,792 acre-feet is discharged annually to San Luis Obispo Creek to provide satisfactory habitat and flow volume for fish species, including steelhead trout.

After accounting for required creek discharge, the remaining treated effluent is available as recycled water for approved non-potable uses. The City currently produces more recycled water than is needed to meet existing recycled water customer demand, and excess recycled water is discharged to San Luis Obispo Creek as needed.

Recycled water is evaluated separately from potable water in this assessment because it is available only for approved non-potable uses and is not available to meet potable water demands. Recycled water offsets potable demand where recycled water service is available, but its use is limited by customer demand, distribution system capacity, seasonal irrigation needs, and regulatory discharge requirements.

Recycled water is distributed through the City’s recycled water system and delivered by a pump station located at the WRRF.

The primary use of recycled water in the City is landscape irrigation, with approximately 75 percent of recycled water demand occurring from May through October. Recycled water is also used for construction-related purposes, including dust control and compaction, through annual construction water permits that the City began issuing in July 2009. The City has four metered hydrant filling stations located throughout City limits to support these and other approved recycled water uses.

The City has identified a seasonal surplus of recycled water available in excess of required San Luis Obispo Creek discharge and existing non-potable demands. A recent upgrade to the WRRF will help the City maximize beneficial use of recycled water, including future consideration of direct or indirect potable reuse. Until potable reuse is implemented, the City is focused on expanding recycled water use within City limits to offset potable water demand where feasible.

Groundwater
The City is currently developing groundwater as a future supplemental potable water supply. The City previously used groundwater for potable purposes but suspended groundwater production in April 2015

2026 Water Supply and Demand Assessment
11 due to water quality concerns associated with tetrachloroethylene (PCE) contamination in the San Luis Obispo Valley Groundwater Basin.

In July 2020, the City received a nearly $2 million planning-phase grant funded through Proposition 1 to further evaluate PCE contamination in the basin. That study was completed in April 2023 and provided a more detailed understanding of the extent of contamination and potential remediation options that could allow the City to restore groundwater production for potable use. In March 2023, the City received an additional implementation-phase grant, with current Proposition 1 implementation funding totaling $7,782,800. The implementation phase includes construction or outfitting of two production wells with treatment systems. These facilities are intended to provide the City with a supplemental potable water supply while also cleaning up contaminated groundwater from within the basin. Several new monitoring wells are also under construction to support evaluation of changing groundwater conditions associated with renewed groundwater pumping and cleanup operations.

Although groundwater is expected to become an important supplemental potable supply in future years, it is not assumed to be available during the Assessment Year. The City anticipates completion of the groundwater pumping wells in spring 2027, with projected groundwater use beginning in July 2027.

Because the Assessment Year covers July 1, 2026 through June 30, 2027, this assessment includes zero acre-feet of groundwater supply.

Existing Infrastructure Capabilities and Plausible Constraints The City’s use of multiple water supply sources provides operational flexibility and helps support overall supply reliability. However, infrastructure limitations, source-specific constraints, water quality conditions, or emergency events can affect the City’s ability to access, convey, treat, or deliver otherwise available supplies. These capabilities and constraints are considered as part of the City’s Assessment Year analysis and are incorporated into the Water Projection Model where applicable.

The most significant infrastructure constraint during the Assessment Year is the temporary limitation on Nacimiento Reservoir deliveries. Although the City’s contractual Nacimiento allocation is 5,482 acre-feet per year, the temporary bypass connection limits the volume of Nacimiento water assumed to be available during the Assessment Year. This assessment assumes 1,806 acre-feet of Nacimiento supply available during the Assessment Year, with no Nacimiento deliveries assumed in February and March 2027.

The City’s Whale Rock and Salinas reservoir conveyance systems are assumed to be available during the Assessment Year. The City is not aware of any infrastructure issues with these systems that are anticipated to restrict delivery volumes during the Assessment Year. However, prolonged disruptions, pipeline failures, pump station issues, or other infrastructure-related constraints could affect the City’s ability to rely on these sources in the manner assumed in this assessment.

The City’s Water Treatment Plant is capable of treating water from the City’s surface water supplies and producing water that meets state and federal drinking water standards. During extreme drought, lower reservoir levels, increased temperatures, wildfire impacts, or degraded source water quality could create additional operational challenges, including algae growth, taste and odor concerns, or other treatment issues. The City has not typically experienced significant water quality limitations that prevent use of its reservoirs, but these conditions remain plausible constraints during severe drought or other unusual events.

Recycled water is delivered through the City’s recycled water system and pump station located at the WRRF. The recycled water pump station does not have backup power during a power outage; however,

2026 Water Supply and Demand Assessment
12 power outages have historically been infrequent, and recycled water is considered a reliable non-potable supply for purposes of this assessment. Recycled water availability may be affected by customer demand, distribution system capacity, seasonal irrigation needs, WRRF operations, and regulatory discharge requirements. Even during periods of extreme drought, the City has produced recycled water in excess of customer demand, with surplus recycled water available during all months of the year after accounting for required San Luis Obispo Creek discharge and existing recycled water uses.

Due to the City’s multi-generational investments in a diverse water supply portfolio, temporary disruptions in any one supply can generally be mitigated through increased use of other available supplies. This operational flexibility is an important component of the City’s water supply reliability.

However, prolonged disruptions, simultaneous source limitations, extreme drought conditions, major infrastructure failures, significant water quality changes, or regulatory constraints could result in supply conditions that differ from those assumed in this assessment. The City will continue to monitor source availability, infrastructure conditions, water quality, and demand trends throughout the Assessment Year and may update its reliability analysis if conditions materially change.

IV. CURRENT-YEAR CONDITIONS INFORMING THE ASSESSMENT
Current Year conditions provide recent observed information used to inform the Assessment Year projection. These conditions include precipitation patterns, reservoir storage levels, recent source use, potable and non-potable water demand, and per-capita water use. While the Assessment Year analysis is forward-looking, Current Year information provides an important baseline for evaluating near-term supply reliability and developing reasonable dry-year demand and supply assumptions.

Current Precipitation and Reservoir Conditions
Precipitation during the Current Year was slightly higher than the average for water years 2013 through 2025. In the City’s watershed areas, precipitation is generally greatest during the winter and early spring months, from November through April, and is typically limited during the summer months. Because significant precipitation is not expected before the start of the Assessment Year, current reservoir storage conditions provide an important indication of near-term supply availability. Current reservoir storage volumes document that Salinas Reservoir is currently 100 percent full, Nacimiento Reservoir is currently 61 percent full, and Whale Rock Reservoir is currently 85.6 percent full. These storage conditions provide the City with substantial operational flexibility heading into the Assessment Year, particularly when considered together with recent water demand levels.

Table 4-1: Precipitation Measured at the SLO Reservoir Station1 Water Year Accumulation (in inches)
2013 12.36
2014 8.50
2015 11.77
2016 19.02
2017 35.34
2018 13.08
2019 27.10
2020 15.60
2021 11.62

2026 Water Supply and Demand Assessment
13 2022 14.82
2023 53.17
2024 24.37
2025 15.11
2013-2025 Average 20.30
2026 (October-May) 24.14
Notes: Precipitation data measured at the SLO Reservoir – P (749) station can be found at:
https://wr.slocountywater.org/site/?site_id=27&view=51a30d03-3991-46af-9d23-7bc0f56a118f.

Current-Year Water Use by Source
Current Year water use provides recent observed data used to inform the Assessment Year demand projection and Water Projection Model assumptions. For the Current Year, July 1, 2025 through June 30, 2026, actual water use data were available for July 2025 through April 2026. Water use for May and June 2026 was estimated because complete data were not available at the time this report was prepared.

Based on actual and estimated monthly data, total Current Year City water use is estimated to be 5,092 acre-feet. This includes approximately 4,824 acre-feet of potable water and 268 acre-feet of recycled water. Potable water use was supplied by Nacimiento Reservoir, Whale Rock Reservoir, and Salinas Reservoir. Recycled water use served approved non-potable demands and offset potable demand where recycled water service was available.

The Current Year reflects reduced use of Nacimiento Reservoir due to the Nacimiento pipeline disruption and temporary bypass limitations. As a result, the City relied more heavily on Whale Rock and Salinas reservoirs than would typically occur under the City’s long-term strategy of maximizing use of Nacimiento water when available. This shift in source use is an important consideration for the Assessment Year because the temporary Nacimiento delivery limitation is expected to continue during the Assessment Year.

Table 4-2: Current-Year Water Use by Source (July 2025 – June 2026) Water Supply Source Volume Used (Acre-Feet) Percent of Total Use Nacimiento Reservoir 1,439 28%
Whale Rock Reservoir 1,837 36%
Salinas Reservoir 1,548 30%
Recycled Water 268 5%
Total City Water Use 5,092 100%
Notes:

1. Water use for May 2026 and June 2026 was estimated as complete data were not available at the time this report was prepared.

2. Water Delivered to Cal Poly is excluded from City demand because Cal Poly has its own water storage and diversion rights in Whale Rock Reservoir.

3. Groundwater was not used for potable purposes during the Current Year.

4. Values are in acre-feet and rounded to the nearest whole number; totals may vary slightly due to rounding.

Current-Year Demand and Per-Capita Water Use

2026 Water Supply and Demand Assessment
14 Current Year potable demand is estimated at 4,824 acre-feet. Including recycled water use, total City water use is estimated at 5,092 acre-feet. Based on these values, estimated per-capita demand, including recycled water use, is approximately 92 gallons per capita per day. Estimated per-capita potable demand, excluding recycled water use, is approximately 87 gallons per capita per day.

Current Year water use remains substantially lower than the City’s long-term planning value of 117 gallons per capita per day. This reflects the continued effect of long-term community water conservation and water use efficiency. The City’s conservation ethic is supported by programs such as water conservation rebates, school education, community outreach, customer water audits, retrofit-upon-sale requirements, leak identification and repair, meter testing and replacement, and use of recycled water for parks and other irrigation demands. These conservation programs are expected to continue in the upcoming year.

Current Year conditions also demonstrate the value of the City’s multi-source water supply portfolio.

Reduced Nacimiento deliveries were offset through increased use of Whale Rock and Salinas reservoirs.

While this approach was appropriate under current reservoir storage conditions, the City’s long-term strategy remains to use Nacimiento water when available to reduce pressure on local reservoir storage and preserve operational flexibility during extended dry periods.

V. ASSESSMENT YEAR SUPPLY AND DEMAND ANALYSIS
Assessment Year Available Potable Supply
The Assessment Year supply and demand analysis evaluates projected potable and non-potable supplies and demands for July 1, 2026, through June 30, 2027, under a dry-year planning condition. The tables in this section are not intended to represent actual measured use or actual hydrology for the Assessment Year. Instead, they compare projected unconstrained demand with projected available supply under the dry-year scenario used for this annual assessment.

The City’s projected Assessment Year potable supply is 6,481 acre-feet. This includes 1,806 acre-feet from Nacimiento Reservoir and 4,675 acre-feet from Salinas and Whale Rock reservoirs. Groundwater is not assumed to be available during the Assessment Year. The General Plan’s separate 500 acre-foot longterm siltation reduction is not applied in this annual assessment because the Assessment Year safe annual yield model runs already account for the near-term effect of siltation on available supplies.

Assessment Year availability from Nacimiento Reservoir differs from Current Year records because the Assessment Year is designed to represent a dry-year planning condition. Under this assumption, the temporary Nacimiento bypass pipeline is expected to be available for a longer portion of the year than reflected in the Current Year record because use of the temporary bypass is limited by flow conditions in the Salinas River. When streamflow is present in the Salinas River, operation of the temporary bypass is restricted. During dry-year conditions, streamflow is expected to begin later in the year and cease sooner, allowing the temporary bypass to be used for a greater portion of the Assessment Year.

Table 5-1: Assessment Year Available Potable Supply by Source (July 2026 – June 2027) Water
Supply
Source
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun TOTAL
(acre-feet)
Nacimiento
Reservoir 216 216 209 216 209 216 105 0 0 105 105 209 1,806

2026 Water Supply and Demand Assessment
15 Salinas and
Whale
Rock
365 365 365 360 335 335 365 480 480 430 430 365 4,675
Total
Available
Potable
Water
Supply
581 581 574 576 544 551 470 480 480 535 535 574 6,481
Notes:

1. Values are in acre-feet and rounded to the nearest whole number; totals may vary slightly due to rounding.

2. Assessment Year availability from Nacimiento Reservoir varies from Current Year records because the Assessment Year is designed to represent a dry-year planning condition, which would result in longer availability of the temporary Nacimiento bypass pipeline.

Assessment Year Available Non-Potable Supply
The City’s projected Assessment Year non-potable recycled water supply 1,296 acre-feet. This volume is representative of the amount of water that could reasonably be treated and delivered to recycled water customers within City limits after the City has met its 1.6 MGD creek discharge requirement.

Recycled water availability is determined through model runs using the City’s Recycled Water Delivery Model. The model allows the City to evaluate recycled water availability based on expected wastewater influent flows, recycled water production, storage tank capacity, pump station capacity, customer demand volumes, seasonal demand patterns, and required discharge volume to San Luis Obispo Creek.

For purposes of the 2026 Annual Water Supply and Demand Assessment, the City uses the model to simulate the amount of recycled water that can reasonably be made available under current system conditions. This approach reflects the practical limitations of the recycled water system by considering both available recycled water supply and the infrastructure needed to store and deliver that supply.

Based on current model inputs, recycled water availability is not limited by the total volume of treated wastewater effluent available for reuse. Instead, the primary limiting factor is the City’s current recycled water pumping capacity at the Water Resource Recovery Facility. As a result, the recycled water volumes reported in this assessment reflect the amount of recycled water that can be delivered using existing infrastructure, rather than the total theoretical volume of recycled water that could be available if additional pumping, storage, or delivery capacity were constructed.

Table 5-2: Assessment Year Available Non-Potable Supply by Source (July 2026 – June 2027) Water
Supply
Source
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun TOTAL
(acre-feet)
Recycled
Water 108 108 108 108 108 108 108 108 108 108 108 108 1,296 Notes: Values are in acre-feet and rounded to the nearest whole number; totals may vary slightly due to rounding.

Assessment Year Unconstrained Potable Demand
Assessment Year unconstrained potable demand represents projected customer potable water use for July 1, 2026, through June 30, 2027. Because this period is in the future, the values shown in Table 5-3 are projections developed from Current Year demand, estimated population growth, and a dry-year demand adjustment. They are not actual measured demands.

2026 Water Supply and Demand Assessment
16 Assessment Year unconstrained potable demand is projected to be 5,355 acre-feet. This demand volume reflects a one percent increase in the City’s population in alignment with the City’s General Plan and observed recent population increases. The Assessment Year demand also reflects a ten percent increase in per-capita water demand to account for increased irrigation demand and other customer demands that may occur during abnormally dry conditions.

Table 5-3: Assessment Year Unconstrained Potable Demand by Customer Class (acre-feet) July 2026 – June 2027
Water Use Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun TOTAL
(acrefeet)
Single Family 176 183 171 165 129 129 134 144 155 149 178 172 1,886 Multi-Family 102 104 108 115 102 97 106 115 105 104 113 104 1,275 Commercial 93 92 89 89 75 83 81 87 89 83 87 89 1,037
Industrial 3 3 6 3 2 3 3 3 3 3 3 3 36
Institutional/
Government 19 20 17 15 10 11 11 12 16 13 16 19 180
Landscape
Irrigation 71 68 59 55 27 24 26 29 48 45 59 65 579
Water Loss 30 30 30 30 30 30 30 30 30 30 30 30 362
Total
Potable
Demand
494 500 479 472 377 378 391 420 446 427 487 482 5,355
Notes:

1. Values are in acre-feet and rounded to the nearest whole number for clear presentation; totals may vary slightly due to rounding.

2. Demand values represent projected unconstrained demand before applying any shortage response actions.

Assessment Year Unconstrained Non-Potable Demand
Assessment Year unconstrained non-potable demand represents projected recycled water demand for July 1, 2026, through June 30, 2027. Recycled water demand is projected separately from potable demand because recycled water is available only for approved non-potable uses and is served by separate recycled water infrastructure.

Assessment Year non-potable recycled water demand is projected to be 306 acre-feet. This demand consists primarily of landscape irrigation, with additional demand from golf course irrigation, construction water use, and utility uses. The projection includes the 10 acre-foot annual increase identified in the City’s recycled water planning assumptions and a ten percent dry-year adjustment to account for expected increases in irrigation demand during warmer and drier conditions.

Table 5-4: Assessment Year Unconstrained Non-Potable Demand (acre-feet) July 2026 – June 2027
Water Use Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun TOTAL (acre-feet)

2026 Water Supply and Demand Assessment
17 Landscape
Irrigation 36.4 38.2 28.9 22.3 9.3 7.0 4.5 8.4 17.1 21.2 24.6 48.8 266.7 Golf Course
Irrigation 4.7 4.3 4.0 2.0 1.3 1.0 1.3 1.3 3.0 3.0 5.0 4.7 35.4 Construction
Use 0.5 0.7 0.3 0.2 0.3 0.1 0.3 0.1 0.1 0.1 0.7 0.3 3.7 Utility Use 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 Total NonPotable
Demand

41.6 43.2 33.1 24.4 10.9 8.1 6.2 9.8 20.2 24.2 30.3 53.8 305.8 Notes:

1. Values are in acre-feet and rounded to the nearest tenth; totals may vary slightly due to rounding.

2. Demand values represent projected unconstrained demand before applying any shortage response actions.

Assessment Year Potable Supply and Demand Comparison
Projected available potable supply exceeds projected unconstrained potable demand in every month of the Assessment Year. The projected annual potable surplus is 1,122 acre-feet. Table 5-5 documents potable water supply availability and demand on a monthly timescale.

Table 5-5: Assessment Year Potable Supply and Demand Comparison (acre-feet) July 2026 – June 2027
Potable
Water Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
TOTAL
(acrefeet)
Anticipated
Unconstrained
Demand (AF)
494 500 479 472 377 379 391 420 446 428 487 482 5355
Anticipated
Total Water
Supply (AF)
581 581 574 576 544 551 470 480 480 535 535 574 6,481
Surplus (AF) 87 81 95 104 167 173 79 60 34 108 48 92 1,126 Percent
Surplus 18 16 20 22 44 46 20 14 8 25 10 19 21%
Water
Shortage
Action
Required (Y/N)

N N N N N N N N N N N N
Notes: Values are in acre-feet and rounded to the nearest whole number; totals may vary slightly due to rounding.

Assessment Year Non-Potable Supply and Demand Comparison Projected available non-potable recycled water supply exceeds projected non-potable demand in every month of the Assessment Year. The City estimates recycled water availability using the City’s Recycled Water Delivery Model, which simulates recycled water availability based on expected wastewater influent volume, storage tank capacity, pump station capacity, demand volume, seasonal demand patterns, and required discharge to San Luis Obispo Creek.

For purposes of the 2026 Annual Water Supply and Demand Assessment, the City’s projected nonpotable recycled water availability reflects the amount of recycled water that can reasonably be delivered with current infrastructure, expected supply volumes, and expected demand conditions. The City’s projected annual deliverable non-potable recycled water supply is 1,296 acre-feet, compared to

2026 Water Supply and Demand Assessment
18 projected unconstrained non-potable demand of 306 acre-feet, resulting in a projected annual nonpotable surplus of 990 acre-feet.

Although treated wastewater effluent is available in volumes greater than current recycled water demand, the City’s ability to make that water available for non-potable use is currently limited by recycled water pumping capacity at the Water Resource Recovery Facility. As a result, the non-potable supply volumes shown in this assessment reflect the City’s deliverable recycled water supply under existing infrastructure conditions, rather than the larger theoretical volume of recycled water that could be available with future pumping, storage, or distribution system upgrades.

Table 5-6: Assessment Year Non-Potable Supply and Demand Comparison (acre-feet) July 2026 – June 2027
NonPotable
Water
Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun
TOTAL
(acrefeet)
Anticipated
Unconstraine
d Demand
(AF)
42 43 33 24 11 8 6 10 20 24 30 54 306
Anticipated
Total Water
Supply (AF)
108 108 108 108 108 108 108 108 108 108 108 108 1,296
Surplus (AF) 66 65 75 84 97 100 102 98 88 84 78 54 990
Percent
Surplus 159 150 226 342 891 1234 1642 998 435 347 257 101 324% Water
Shortage
Action
Required
(Y/N)

N N N N N N N N N N N N
Notes: Values are in acre-feet and rounded to the nearest whole number; totals may vary slightly due to rounding.

Water Shortage Determination
Based on the Assessment Year supply and demand comparison, the City does not anticipate a water shortage during any month from July 2026 through June 2027. Projected available potable supply exceeds projected unconstrained potable demand on both an annual and monthly basis. Projected nonpotable recycled water supply also exceeds projected non-potable demand in every month.

In addition to the monthly and annual supply and demand comparison, the City evaluates projected years of available water supply using the Water Projection Model. The model indicates that, under the input conditions used for this assessment, the City has more than 10 years of available water supply. Because no monthly shortage is projected and the City remains above the five-year availability threshold identified in the WSCP, the City does not plan to implement WSCP response actions during the Assessment Year.

Although no shortage is projected, the City will continue to monitor water supply and demand conditions throughout the Assessment Year. If actual conditions differ materially from the assumptions used in this assessment, the City may reevaluate supply reliability and implement appropriate actions under the WSCP.

2026 Water Supply and Demand Assessment
19 Conditions that could require reassessment include, but are not limited to:
 Further disruption to Nacimiento deliveries;
 Unexpected limitations on Salinas or Whale Rock reservoir operations;  Significant water quality changes affecting treatment;  Higher-than-projected customer demand;
 Major infrastructure failure;
 Regulatory or environmental constraints affecting source availability; or  Extended drought conditions more severe than assumed in this assessment.

If a shortage is identified, the City would implement the applicable WSCP stage and associated response actions. These actions may include public outreach, increased water use monitoring, restrictions on discretionary water uses, outdoor irrigation limitations, enforcement actions, and other measures necessary to reduce demand and extend available supplies.

Monitoring, Communication, Compliance, and Enforcement
The City reads water meters monthly to collect water consumption data for billing, tracking, analysis, and state reporting. Collection of monthly water use data allows the City to evaluate demand trends, identify potential changes in customer behavior, and determine whether projected demands remain consistent with actual use.

Monitoring and reporting are fundamental to water supply planning and shortage management. The City will continue to monitor observed water use, reservoir storage volumes, source availability, infrastructure status, water quality, and recycled water availability throughout the Assessment Year. If conditions differ from the assumptions used in this assessment, the City may update the Water Projection Model and reevaluate whether WSCP response actions are needed.

The City’s WSCP provides the framework for responding to water shortages by reducing demand, extending available water supplies, preserving water for public health and safety, and allowing time for additional rainfall or supplemental supplies to improve supply conditions. If shortage response actions become necessary, the City’s response may include public outreach, water efficiency measures, outdoor irrigation restrictions, enforcement actions, and other measures that increase in intensity as shortage conditions become more severe. The City would monitor the effectiveness of implemented actions by reviewing monthly water consumption, customer class demand trends, community response, enforcement activity, and associated revenue and expenditure impacts. Based on these analyses, staff would recommend program refinements to the City Council as needed.

VI. SUMMARY AND FINDINGS
This 2026 Water Supply and Demand Assessment evaluates the City’s water supply reliability for the period of July 1, 2026, through June 30, 2027. The assessment uses Current Year water use information, historical and seasonal demand patterns, current supply conditions, source-specific availability, infrastructure constraints, and dry-year assumptions to evaluate whether available supplies are sufficient to meet projected Assessment Year demands.

For potable water, the City’s projected Assessment Year demand is 5,355 acre-feet, and projected available supply is 6,481 acre-feet, resulting in an estimated potable surplus of 1,126 acre-feet. Projected available potable supply exceeds projected potable demand in every month of the Assessment Year.

2026 Water Supply and Demand Assessment
20 The Assessment Year potable supply assumptions include restricted Nacimiento Reservoir availability due to the temporary bypass connection, rather than the City’s full 5,482 acre-foot annual entitlement.

The assessment also includes available supply from Salinas and Whale Rock reservoirs based on Assessment Year model runs that account for the near-term effect of siltation, and zero acre-feet of groundwater because groundwater is not assumed to be available during the Assessment Year. The General Plan’s policy-driven 500 acre-foot long-term siltation reduction is not applied in this annual assessment because this report evaluates near-term supply reliability for the Assessment Year rather than long-term supply availability for future development.

For non-potable recycled water, the City’s projected Assessment Year demand is approximately 306 acrefeet, and projected deliverable supply is 1,296 acre-feet, resulting in an estimated non-potable surplus of 990 acre-feet. Projected available non-potable recycled water supply exceeds projected non-potable demand in every month of the Assessment Year. Recycled water is evaluated separately from potable water because it is available only for approved non-potable uses and is limited by customer demand, system capacity, seasonal irrigation patterns, WRRF operations, and regulatory discharge requirements.

Based on the monthly supply and demand comparison, the City does not anticipate a water shortage during the Assessment Year and does not plan to implement WSCP response actions. In addition, the Water Projection Model indicates that the City has more than 10 years of available water supply under the input conditions used for this assessment, which is more than the City’s five-year WSCP threshold for shortage response consideration.

The City will continue to monitor water supply and demand conditions throughout the Assessment Year.

While the City’s diverse water supply portfolio provides reliability and operational flexibility, actual conditions may differ from the assumptions used in this assessment due to infrastructure disruptions, extreme drought, water quality changes, regulatory constraints, or higher-than-projected demands. If conditions materially change, the City is prepared to reassess supply reliability using the Water Projection Model and implement appropriate response actions under the WSCP, if needed.

DRAFT
2025 Urban Water
Management Plan
(PUBLIC REVIEW DRAFT)
This plan was adopted on ________, 2026
pursuant to San Luis Obispo City Council
Resolution No. ________ (2026 series)
San Luis Obispo City Council
Erica A. Stewart, Mayor
Emily Francis, Vice Mayor
Jan Marx
Michelle Shoresman
Michael R. Boswell
Plan Prepared by:

City of San Luis Obispo, Public Works and Utilities Department Utilities Branch
879 Morro Street
San Luis Obispo, CA 93401

DRAFT
2025 Urban Water Management Plan
2 TABLE OF CONTENTS
LIST OF TABLES............................................................................................................................6 ABBREVIATIONS AND ACRONYMS ...............................................................................................7 EXECUTIVE SUMMARY AND LAY DESCRIPTION.............................................................................8 CHAPTER 1: PLAN INTRODUCTION AND OVERVIEW ...................................................................10

1.1 Urban Water Management Planning Act ......................................................................10

1.2 Purpose of the 2025 UWMP.........................................................................................10

1.3 General Plan and UWMP Interface ..............................................................................11

1.4 Organization of the UWMP ..........................................................................................11

1.5 Relationship to Other Planning Documents .................................................................13 CHAPTER 2: PLAN PREPARATION ...............................................................................................13

2.1 Agency Coordination ..................................................................................................13

2.2 Public Participation and Plan Adoption........................................................................14

2.3 Plan Implementation ..................................................................................................14

2.4 Standardized Tables ...................................................................................................15

2.5 Compliance Checklist ................................................................................................15 CHAPTER 3: SERVICE AREA DESCRIPTION..................................................................................15

3.1 Introduction ...............................................................................................................15

3.2 Service Area Overview ................................................................................................16

3.3 Climate and Hydrologic Conditions.............................................................................16

3.4 Water System Overview ..............................................................................................17

3.4.1 Water Supply Sources.............................................................................................17

3.4.2 Water Treatment Facilities ..................................................................................18

3.4.3 Potable Water Distribution System ......................................................................19

3.4.4 Recycled Water System ......................................................................................20

3.5 Existing Population and Demographic Characteristics .................................................20

3.6 Future Population Projections.....................................................................................21

3.7 Land Use Characteristics and Planning Assumptions ..................................................22 CHAPTER 4: WATER USE CHARACTERIZATION............................................................................23

4.1 Introduction ...............................................................................................................23

4.2 Demand Sector Definitions .........................................................................................24

4.3 Historical Water Demand............................................................................................24

DRAFT
2025 Urban Water Management Plan
3 4.4 Current Water Demand...............................................................................................25

4.5 Future Water Demand Projections ..............................................................................26

4.6 Distribution System Water Loss ..................................................................................28 CHAPTER 5: SB X7-7 BASELINES, 2020 TARGETS, AND 2025 REPORTING ....................................30

5.1 Introduction and Regulatory Context...........................................................................30

5.2 Baseline and Target Summary.....................................................................................30

5.3 SB X7-7 Compliance and 2025 Reporting.....................................................................30 CHAPTER 6: NORMAL-YEAR WATER SUPPLY CHARACTERIZATION..............................................31

6.1 Introduction ...............................................................................................................31

6.2 Water Supplies...........................................................................................................32

6.2.1 Salinas Reservoir....................................................................................................32

6.2.2 Whale Rock Reservoir.............................................................................................33

6.2.3 Nacimiento Reservoir .............................................................................................36

6.2.4 Groundwater..........................................................................................................37

6.2.5 Recycled Water ......................................................................................................39

6.3 Water Supply Modeling and Yield Assessment.............................................................42

6.3.1 Overview of Water Supply Planning Methodology .....................................................42

6.3.2 Salinas and Whale Rock Safe Annual Yield Modeling and Reliability..........................43

6.3.3 Nacimiento Water Supply Reliability........................................................................45

6.3.4 Groundwater Supply Reliability / Planned Groundwater Supply ................................46

6.3.5 Recycled Water Supply Reliability ...........................................................................47

6.4 Current Year Water Use and Normal-Year Supply Availability .......................................48

6.4.1 Current Year Water Supply and Demand..................................................................48

6.4.2 Projected Normal-Year Potable Water Supply Volumes............................................48

6.4.3 Projected Normal-Year Non-Potable Water Supply Volumes ....................................49

6.4.4 Energy Use Information...........................................................................................50

6.5 Planned Water Supply Projects and Programs .............................................................51

6.6 Climate Change and Water Supply Considerations......................................................52

6.7 Transfers and Exchanges ............................................................................................52 CHAPTER 7: WATER SERVICE RELIABILITY AND DROUGHT RISK ASSESSMENT ............................53

7.1 Introduction ...............................................................................................................53

7.2 Basis of Water Service Reliability Assessment .............................................................53

DRAFT
2025 Urban Water Management Plan
4 7.3 Water Year Type Characterization ...............................................................................54

7.4 Normal-Year Water Service Reliability .........................................................................55

7.5 Single Dry-Year Water Service Reliability .....................................................................56

7.6 Multiple Dry-Year Water Service Reliability ..................................................................56

7.7 Five-Year Drought Risk Assessment ............................................................................58

7.8 Reliability Findings and Relationship to the WSCP .......................................................59 CHAPTER 8: WATER SHORTAGE CONTINGENCY PLANNING & EMERGENCY SUPPLY RESILIENCY .................................................................................................................................................60

8.1 Introduction ...............................................................................................................60

8.2 Potential Causes of Water Shortage Conditions...........................................................60

8.2.1 Seismic Risk Assessment and Mitigation .................................................................61

8.3 City Water Shortage Contingency Plan ........................................................................62

8.4 Water Shortage Contingency Plan Adoption, Submittal, and Availability .......................62 CHAPTER 9: DEMAND MANAGEMENT MEASURES.......................................................................63

9.1 Introduction ...............................................................................................................63

9.2 Water Conservation Program Goals and Objectives .....................................................63

9.3 Historical Conservation Efforts ...................................................................................64

9.4 Demand Management Measure Implementation (2021-2025) ......................................64

9.5 Water Waste Prevention Ordinances...........................................................................65

9.6 Metering, Billing, and Advanced Metering Infrastructure...............................................65

9.7 Conservation Pricing and Water Rate Structure ...........................................................66

9.8 Public Education, Outreach, and Technical Assistance................................................66

9.9 Programs to Assess and Manage Distribution System Losses.......................................66

9.10 Water Conservation Program Coordination and Staffing...............................................67

9.11 Other Significant Demand Management Measures ......................................................67

9.11.1 Recycled Water Use............................................................................................67

9.11.2 Conservation Reviews, Audits, and Customer Support.........................................67

9.11.3 Complimentary Devices and Rebate Programs ....................................................68

9.11.4 MWELO, Landscape Water Budgets, and CII Water Use .......................................68

9.12 Planned Demand Management Measures and Performance Tracking...........................69

9.13 Relationship to Water Supply Reliability and Shortage Planning....................................69 CHAPTER 10: ADOPTION, SUBMITTAL, AND IMPLEMENTATION...................................................70

10.1 Introduction ...............................................................................................................70

DRAFT
2025 Urban Water Management Plan
5 10.2 Notice of Plan Preparation and Agency Coordination ...................................................70

10.3 Public Review Draft and Availability for Public Inspection.............................................70

10.4 Public Hearing and Adoption.......................................................................................71

10.5 Submittal of Adopted UWMP and WSCP......................................................................71

10.6 Public Availability After Filing ......................................................................................72

10.7 Plan Implementation ..................................................................................................72

10.8 Amendments to the Adopted Plan...............................................................................72 APPENDICES .............................................................................................................................73 Appendix A – DWR Standardized Submittal Tables ...................................................................73 Appendix B – DWR UWMP Compliance Checklist.....................................................................95 Appendix C – Public Notices, Agency Coordination, and Adoption Documentation ...................99 Appendix D – Water Loss Audit Documentation .....................................................................103 Appendix E – Safe Annual Yield Technical Memorandum........................................................104 Appendix F – Annual Water Supply and Demand Assessments...............................................105 Appendix G – Seismic Risk / Hazard Mitigation Plan Reference ...............................................106 Appendix H – Water Shortage Contingency Plan ....................................................................108

DRAFT
2025 Urban Water Management Plan
6 LIST OF TABLES
Table 3-1: San Luis Obispo Climate ...........................................................................................................16 Table 3-2: Top Employers...........................................................................................................................21 Table 3-3: City Population Projections........................................................................................................22 Table 4-1: 2025 Potable Water Use by Sector ...........................................................................................25 Table 4-2: Projected Future Potable Water Demand by Year ....................................................................27 Table 4-3: Projected Future Non-Potable Water Demand by Sector..........................................................27 Table 4-4: Common Water Loss & Unbilled Consumption Types ..............................................................28 Table 4-5: Water Loss Audit Data and Results...........................................................................................29 Table 5-1: SB X7-7 Baseline and Target Summary....................................................................................30 Table 6-1: Whale Rock Reservoir Downstream Entitlements.....................................................................35 Table 6-2: Surface Water Reservoir Characteristics ..................................................................................37 Table 6-3: Groundwater Pumping Volumes................................................................................................38 Table 6-4: Treated Wastewater Uses within City in FY 2025 (in acre-feet)................................................40 Table 6-5: FY 2025 Recycled Water Demand by Customer Class.............................................................41 Table 6-6: FY 2025 Actual Water Supply Use by Source...........................................................................48 Table 6-7: Projected Normal-Year Potable Water Supply Volumes (in acre-feet)......................................49 Table 6-8: Projected Normal-Year Non-Potable Water Supply Volumes (in acre-feet)..............................50 Table 6-9: FY 2025 Potable Water-Related Electricity Use........................................................................51 Table 7-1: Normal-Year Potable Water Reliability ......................................................................................55 Table 7-2: Normal-Year Non-Potable Reliability .........................................................................................55 Table 7-3: Single Dry-Year Potable Water Reliability .................................................................................56 Table 7-4: Single Dry-Year Non-Potable Water Reliability .........................................................................56 Table 7-5: Multiple Dry-Year Potable Water Reliability...............................................................................57 Table 7-6: Multiple Dry-Year Non-Potable Water Reliability.......................................................................57 Table 7-7: Five-Year Drought Risk Assessment - Potable Water...............................................................59 Table 7-8: Five-Year Drought Risk Assessment - Non-Potable Water.......................................................59 Table 9-1: Demand Management Measure Implementation Summary (2021-2025) .................................65 Table 10-1: Required Post-Adoption Submittals.........................................................................................71

DRAFT
2025 Urban Water Management Plan
7 ABBREVIATIONS AND ACRONYMS
ADU - Accessory Dwelling Unit
AF - Acre-Foot or Acre-Feet
AFY (or afy) - Acre-Feet per Year
AMI - Advanced Metering Infrastructure
AWWA - American Water Works Association
CALGreen - California Green Building Standards Code
CAWO - Cayucos Area Water Organization
CII - Commercial, Industrial, and Institutional water use sectors CIMIS - California Irrigation Management Information System CWC - California Water Code
CY - Calendar Year
DDW - State Water Resources Control Board, Division of Drinking Water DMMs - Demand Management Measures
DWR - California Department of Water Resources
EPA - U.S. Environmental Protection Agency
ETo - Reference Evapotranspiration
FY - Fiscal Year
GPCD (or gpcd) - Gallons per Capita per Day
GSP - Groundwater Sustainability Plan
ILI – Infrastructure Leakage Index
LUE - Land Use Element
MGD - Million Gallons per Day
MJHMP - Multi-Jurisdictional Hazard Mitigation Plan
MWELO - Model Water Efficient Landscape Ordinance
NPDES - National Pollutant Discharge Elimination System PCE - Tetrachloroethylene
RWQCB - Regional Water Quality Control Board
SAY - Safe Annual Yield
SB X7-7 - Senate Bill Seven of the Senate’s Seventh Extraordinary Session of 2009 SDWA - Safe Drinking Water Act
SGMA - Sustainable Groundwater Management Act
SWRCB - State Water Resources Control Board
THMs/TTHMs- Trihalomethanes/Total Trihalomethanes
UWUO - Urban Water Use Objective
UWMP - Urban Water Management Plan
WRRF - City of San Luis Obispo Water Resources Recovery Facility WSCP - Water Shortage Contingency Plan
WTP - City of San Luis Obispo Water Treatment Plant
WWE - Water and Wastewater Element

DRAFT
2025 Urban Water Management Plan
8 EXECUTIVE SUMMARY AND LAY DESCRIPTION
The City of San Luis Obispo prepared this 2025 Urban Water Management Plan (UWMP) to evaluate current and future water use, describe the City’s available water supplies, assess water supply reliability, and document the City’s approach to drought planning and water shortage response. Urban Water Management Plans are required by State law and are updated every five years accordingly. This UWMP evaluates the City’s water supply reliability through 2050 and supports coordination between water supply planning, land use planning, infrastructure planning, drought preparedness, and the City’s General Plan.

The City provides potable water service within the city limits and delivers recycled water for approved nonpotable uses, including landscape irrigation, construction-related uses, and other authorized uses. The City’s water supply portfolio includes multiple surface water reservoirs, recycled water, and planned groundwater production. This diverse water supply portfolio has been developed over many decades and helps reduce overreliance on any single water source.

The City’s primary potable water supplies are Salinas Reservoir, Whale Rock Reservoir, and Nacimiento Reservoir. Salinas and Whale Rock reservoirs are local surface water supplies that are operated together and evaluated through a combined safe annual yield analysis. Nacimiento Reservoir provides a separate contractual supply that is delivered through the Nacimiento Water Project. The City is also implementing projects to restore groundwater production as a supplemental potable water supply. Groundwater is expected to improve supply diversification and provide additional local water supply reliability once extraction, treatment, regulatory, and operational requirements are in place.

Recycled water is produced at the City’s Water Resource Recovery Facility and is used for approved nonpotable purposes. Recycled water offsets potable water demand where recycled water service is available, but it is evaluated separately from potable water because it is not available to meet drinking water demands.

The amount of recycled water that can be beneficially used depends on customer demand, seasonal irrigation patterns, required discharge to San Luis Obispo Creek, storage capacity, pumping capacity, and recycled water distribution infrastructure. The City expects recycled water use to continue growing over time as additional customers, system improvements, and beneficial use opportunities become feasible.

This UWMP distinguishes between long-term water supply planning and near-term operational reliability analysis. For long-term planning, the City uses General Plan and Water and Wastewater Element assumptions to evaluate whether existing and planned supplies are sufficient to serve projected growth over the UWMP planning horizon. Long-term demand projections are based on General Plan population assumptions and the City’s 117 gallons per capita per day planning value. This approach is intentionally conservative because it evaluates water supply sufficiency many years into the future, when population, land use, customer water use patterns, climate, regulations, infrastructure conditions, and source availability may differ from current conditions.

For near-term operational reliability analysis, the City uses more current information, including actual reservoir storage, recent water use, current population estimates, seasonal demand patterns, source availability, known infrastructure constraints, recycled water availability, groundwater project status, and dry-year assumptions. These near-term analyses include the City’s annual Water Supply and Demand Assessments, Water Shortage Contingency Plan implementation, and the five-year drought risk assessment required as part of this UWMP. This approach is more appropriate for near-term analysis because the City has better information about actual operating conditions and expected customer demand over the next one to five years than it does over the full multi-decade UWMP planning horizon.

The City’s current water use remains substantially lower than the long-term 117 gallons per capita per day planning value used for multi-decade planning. This reflects the community’s long-standing water conservation ethic, water efficiency improvements, recycled water use, and ongoing demand management programs. The UWMP continues to use the higher 117 gallons per capita per day value for long-term water supply planning because it provides a conservative planning buffer for future uncertainty. However, nearPage 334 of 546 DRAFT
2025 Urban Water Management Plan
9 term assessments use more current demand information to avoid overstating expected customer demand during upcoming assessment periods.

Based on the analysis in this UWMP, the City’s existing and planned water supplies are projected to be sufficient to meet projected demands through 2050 under normal-year, single dry-year, and multiple dryyear conditions. The City’s long-term water supply planning values include the City’s contractual supply from Nacimiento Reservoir, the combined safe annual yield of Salinas and Whale Rock reservoirs, planned groundwater production when available, recycled water use, and long-term planning adjustments to account for reservoir siltation.

The City’s five-year drought risk assessment provides a more focused near-term evaluation of water supply reliability. This analysis evaluates whether projected supplies are sufficient to meet projected demands during the five-year drought risk assessment period. The City’s Water Projection Model supports this analysis by evaluating how current and projected demands affect available supplies and by estimating the number of years of available water supply remaining under the input conditions. This helps the City determine whether it should remain in normal operations or consider response actions under the Water Shortage Contingency Plan.

The City’s Water Shortage Contingency Plan provides the framework for responding to water shortage conditions. Water shortages can result from drought, infrastructure failure, water quality issues, regulatory requirements, seismic events, wildfire impacts, power outages, or other emergency conditions that affect the City’s ability to access, convey, treat, or deliver water. The Water Shortage Contingency Plan includes staged response actions that may be implemented if available supplies decline or if other conditions create a water shortage.

The City’s major water supply reliability efforts include:
• Restoring full Nacimiento Reservoir conveyance capacity following damage to the Nacimiento transmission system;
• Restoring groundwater production as a supplemental potable water supply; • Continuing to optimize and expand recycled water use where feasible; • Evaluating potable reuse opportunities;
• Participating in regional studies related to desalination feasibility; • Continuing long-term water conservation and demand management programs; and • Investing in water treatment, transmission, storage, distribution, recycled water, groundwater, and emergency response infrastructure.

This UWMP concludes that the City’s diversified water supply portfolio, planned groundwater restoration, recycled water program, conservation efforts, and ongoing infrastructure investments provide a reliable basis for meeting projected water demands through 2050. The City’s multi-generational investments in surface water supplies, recycled water, water treatment, conservation, and system resiliency have positioned the City to meet expected demands during normal years and through periods of extended drought. The investments the City has made reduce overreliance on any single source of supply and provide the operational flexibility needed to respond to changing hydrologic, regulatory, infrastructure, and demand conditions. The City will continue to monitor water supply conditions, update planning assumptions as new information becomes available, implement demand management measures, pursue planned supply and infrastructure improvements, and use the Water Shortage Contingency Plan to guide response actions if shortage conditions occur.

DRAFT
2025 Urban Water Management Plan
10 CHAPTER 1: PLAN INTRODUCTION AND OVERVIEW

1.1 Urban Water Management Planning Act
The City’s Urban Water Management Plan (UWMP) was prepared in accordance with the Urban Water Management Planning Act (UWMP Act). The UWMP Act is defined by the California Water Code (CWC), Division 6, Part 2.6, and Sections 10610 through 10656. The UWMP Act requires every urban water supplier that provides water for municipal purposes to more than 3,000 service connections or supplies more than 3,000 acre-feet (AF) of water annually, to adopt and submit a plan every five years to the California Department of Water Resources (DWR).

Since its passage in 1983, the UWMP Act has been amended periodically to address evolving water management challenges and statewide policy objectives. Significant amendments include the 2009 enactment of Senate Bill X7-7 (SB X7-7), which required each urban retail water supplier to develop urban water use targets to help meet the statewide 20 percent water use reduction goal by 2020 and an interim ten percent goal by 2015.

Over time, the UWMP Act has expanded to place greater emphasis on long-term water supply reliability, water use efficiency, drought preparedness, water loss reduction, integrated water management planning, and resiliency in response to changing hydrologic and climate conditions. These considerations are reflected throughout the City’s 2025 UWMP and Water Shortage Contingency Plan (WSCP).

The City’s 2025 UWMP serves as a foundational planning document and source of information for preparation of Water Supply Assessments (Water Code Section 10910 et seq.) and a Written Verification of Water Supply (Government Code Section 66473.7), both of which require detailed evaluation of water supply availability prior to approval of certain development projects.

1.2 Purpose of the 2025 UWMP
The 2025 UWMP serves as both a regulatory compliance document and a long-range water resources planning tool. Understanding the purpose and intended use of the UWMP provides context for how the document supports water supply planning, infrastructure investment, drought preparedness, regulatory compliance, land use coordination, and long-term management of the City’s water system. The UWMP is intended to provide a technical and policy framework that can be referenced by City staff, decision-makers, regulatory agencies, and the public as water management conditions evolve over time.

The purpose of the 2025 UWMP is to:

1. Assess past, current, and future water use in the community;

2. Describe the existing and planned potable and non-potable water supplies, water rights, infrastructure, and water system operations;

3. Evaluate water supply reliability under normal, single dry-year, and multiple dry-year conditions;

4. Assess drought risk and establish a framework for responding to water shortages through the WSCP;

5. Support long-term water supply planning and coordination with land use planning efforts, including the City’s General Plan and regional planning initiatives;

6. Document the City’s water demand management measures and ongoing conservation efforts;

7. Demonstrate compliance with applicable provisions of the Urban Water Management Planning Act and Senate Bill X7-7;

8. Provide a technical and policy reference for the City’s water system, including its background, operations, infrastructure, regulatory considerations, and future planning;

9. Serve as a source document on the history, management, and reliability of the water supply system;

10. Support planning for future infrastructure improvements, changing hydrologic conditions, regulatory

DRAFT
2025 Urban Water Management Plan
11 requirements, and climate-related uncertainties; and

11. Maintain eligibility for State grants, loans, and other funding opportunities related to water infrastructure and water management.

The 2025 UWMP evaluates current and projected water demands and available water supplies through the year 2050, describes the City’s water treatment and distribution systems, assesses water supply reliability and drought risk, and identifies water demand management measures intended to support long-term water supply reliability and resiliency. Because the UWMP addresses both long-term supply reliability and nearterm drought risk, the Plan distinguishes between long-term water supply planning and near-term operational reliability analysis. Long-term water supply planning is guided by the General Plan and Water and Wastewater Element (WWE) and is used to evaluate whether existing and planned supplies are sufficient to support projected growth through the UWMP planning horizon. Near-term operational reliability analysis is used for upcoming single-year assessments, WSCP implementation, and the five-year drought risk assessment, where current storage, recent demand, infrastructure conditions, and known source constraints provide a more accurate basis for evaluating potential shortages.

1.3 General Plan and UWMP Interface
The City’s General Plan WWE has served as a primary policy framework guiding the provision of water and wastewater services since its adoption in 1987. The WWE recognizes the critical role water resources and utility infrastructure play in supporting the community and the influence that water-related policies have on growth, development, land use, and community character.

The WWE translates the land use assumptions identified in the General Plan Land Use Element (LUE) into projected water supply and wastewater service demands and establishes policies intended to ensure adequate utility services are available to support existing and future development. Population projections, land use assumptions, and anticipated development patterns identified in the General Plan and other regional and California State adopted data and documents serve as important planning inputs for the UWMP.

The UWMP supports and informs the WWE by providing detailed analysis of water supply availability, projected water demands, system operations, drought risk, and long-term water supply reliability. Together, these documents help ensure that water supply planning, infrastructure planning, and land use planning remain closely coordinated.

The Water Management section of the WWE was originally developed during a period of water supply constraint in the late 1980s, when planning efforts focused heavily on the allocation and management of limited water supplies. The WWE has subsequently been revised periodically, most recently in 2025, to reflect updated planning assumptions, regulatory requirements, and long-term water resource management considerations. These updates continue to emphasize balancing available water supplies with existing demands and future growth anticipated under the General Plan.

The General Plan and WWE provide the policy basis for the City’s long-term water demand and supply planning. For long-term planning, projected demands are based on General Plan population assumptions and the City’s 117 gpcd planning value, while supply availability is based on established long-term planning values for the City’s water supply portfolio. The UWMP also includes near-term operational reliability analysis for the five-year drought risk assessment. That near-term analysis is not intended to replace the General Plan and WWE accounting framework; rather, it evaluates whether current and near-term supplies are sufficient to meet expected demands during the upcoming one- to five-year period.

1.4 Organization of the UWMP
The City’s 2025 UWMP is organized into chapters addressing the major planning components required under the UWMP Act. The UWMP includes evaluation of water demands, available water supplies, water supply reliability, drought risk, water shortage response actions, and water demand management measures, as required by the California Water Code. The organization of the UWMP is summarized below.

DRAFT
2025 Urban Water Management Plan
12 Executive Summary
Provides a high-level overview of the City’s water system, water supplies, projected water supply and demand, water supply reliability, drought preparedness, and major findings of the 2025 UWMP.

Chapter 1: Plan Introduction and Overview
Provides background on the Urban Water Management Planning Act, the purpose of the UWMP, and the relationship between the UWMP and other planning documents.

Chapter 2: Plan Preparation
Describes the basis for preparing the UWMP, coordination and outreach efforts, and plan preparation requirements.

Chapter 3: Service Area Description
Provides an overview of the City’s service area, population, climate, land use characteristics, and water service area.

Chapter 4: Water Use Characterization
Describes historical, current, and projected potable and non-potable water demands within the City’s service area.

Chapter 5: SB X7-7 Baselines, 2020 Targets, and 2025 Reporting Documents compliance with Senate Bill X7-7 urban water use reduction requirements and associated reporting metrics.

Chapter 6: Normal-Year Water Supply Characterization
Describes the City’s water supply sources, water rights, infrastructure, water system operations, and projected future water supplies.

Chapter 7: Water Service Reliability and Drought Risk Assessment Evaluates water supply reliability under normal, single dry-year, and multiple dry-year conditions and includes the City’s Drought Risk Assessment.

Chapter 8: Water Shortage Contingency Planning & Emergency Supply Resiliency Describes the City’s response framework for water shortage conditions, supply interruptions, and drought emergencies.

Chapter 9: Demand Management Measures
Summarizes the City’s water conservation and demand management programs and ongoing efforts to improve water use efficiency.

Chapter 10: Adoption, Submittal, and Implementation
Documents the public review, adoption, submittal, and implementation process for the UWMP.

Appendices
Provide supporting technical information, reference materials, submittal tables, and supplemental documentation associated with the UWMP.

The City’s 2025 Water Shortage Contingency Plan (WSCP) is published as a separate document and is incorporated by reference into this UWMP in accordance with Water Code requirements. The WSCP may be amended separately from the UWMP if necessary to address changing conditions, regulatory requirements, or operational needs.

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2025 Urban Water Management Plan
13 1.5 Relationship to Other Planning Documents
The City’s 2025 UWMP was developed in coordination with other local and regional planning efforts related to water resources, infrastructure planning, emergency preparedness, sustainability, and long-term community development. These planning documents provide supporting technical information, policy direction, operational guidance, and planning assumptions that help inform the UWMP and promote consistency between related planning efforts.

The UWMP both supports and relies upon information contained in other planning documents prepared by the City and regional agencies. These documents collectively assist the City in evaluating water supply reliability, infrastructure needs, drought preparedness, emergency response capabilities, regulatory compliance obligations, and long-term water resource management strategies.

Examples of planning documents include, but are not limited to:
• City of San Luis Obispo General Plan and Water and Wastewater Element • 2025 Water Shortage Contingency Plan
• Long-term water infrastructure replacement plans
• San Luis Obispo Valley Basin Groundwater Sustainability Plan • County of San Luis Obispo Integrated Regional Water Management Plan • Recycled water and wastewater management plans
• Emergency response plans and hazard mitigation plans
Information developed through these planning efforts was incorporated into the UWMP where appropriate to support consistency between water supply planning, land use planning, infrastructure planning, and longterm resource management objectives. The UWMP also serves as a reference document for future planning studies, infrastructure projects, environmental review processes, and water resource management decisions undertaken by the City and other agencies. Because many water resource management issues extend beyond jurisdictional boundaries, coordination between local and regional planning efforts remains an important component of long-term water supply reliability planning.

CHAPTER 2: PLAN PREPARATION

2.1 Agency Coordination
The UWMP Act requires the City to coordinate preparation of the UWMP with appropriate agencies, including cities and counties within which the City provides water, water suppliers that share a common source, water management agencies, and other relevant public agencies. This chapter describes the City’s coordination efforts during preparation of the 2025 UWMP. Formal notice, public hearing, adoption, and post-adoption submittal requirements are documented separately in Chapter 10.

The City’s water supply portfolio includes several regional or jointly managed water resources, including Whale Rock Reservoir and Nacimiento Reservoir. Although these resources involve multiple agencies, the City’s projected water supply availability in this UWMP is based on defined water rights, ownership shares, contractual entitlements, and adopted planning assumptions. The City’s use of these supplies is therefore evaluated based on the City’s established rights and allocations, rather than on unallocated supplies that would otherwise be available to other agencies. Coordination with partner agencies remains important for reservoir operations, conveyance reliability, long-term planning, and emergency response; however, the City’s projected demands and supplies in this UWMP are not assumed to reduce the established entitlements or allocations of other participating agencies.

Whale Rock Reservoir Commission
Whale Rock Reservoir provides water to the City, California Polytechnic State University (Cal Poly), the California Men’s Colony, and the town of Cayucos. The Whale Rock Commission oversees the reservoir

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2025 Urban Water Management Plan
14 operations and is made up of representatives from the City, California Men’s Colony, and Cal Poly, as well as a representative from the State Department of Water Resources. The City provides staff oversight of daily operations and maintenance activities of Whale Rock Reservoir. These staff members work closely with staff from the Commission member agencies to address water planning issues. The City most recently met with representatives from Cal Poly, a Whale Rock Commission Member, to discuss community water use and population growth forecasts for both entities on March 17, 2026.

Cayucos Area Water Organization
The Cayucos Area Water Organization (CAWO) includes the three water purveyors that serve the town of Cayucos (Paso Robles Beach Water Association, Morro Rock Mutual Water Company, County Service Area 10A) and the Cayucos-Morro Bay Cemetery District. The Whale Rock Commission and CAWO have an agreement which includes a provision to provide up to 600-acre feet of water per year from the reservoir.

The agreement dates to the period when the dam was being planned and constructed. The agreement has been amended since that time. The water provided to the CAWO is delivered from the Whale Rock pipeline to the Cayucos Water Treatment Plant operated by the County of San Luis Obispo (County). City of San Luis Obispo staff attend CAWO meetings on a regular basis and communicate with agencies regarding Whale Rock storage volumes, availability, and any periods when water from the reservoir may not be accessible.

Nacimiento Project Commission
The County has an entitlement of 17,500-acre feet of water from Nacimiento Reservoir and acts as the wholesaler of this water supply. The County oversees the project that delivers water from Nacimiento Reservoir to agencies participating in the Nacimiento Water Project. The current participating entities include the cities of Paso Robles and San Luis Obispo, Atascadero Mutual Water Company, Templeton Community Services District, Santa Margarita Ranch, Bella Vista Mobile home park, and County Service Area 10A (Cayucos).

The Nacimiento Project Commission is made up of representatives from each of the four original participating agencies’ governing boards, as well as a representative from the County Flood Control and Water Conservation District (i.e. County Board of Supervisors). The Nacimiento Project Commission provides oversight and recommendations to the District regarding project operations and maintenance and the associated budget. The County, as the water supply “wholesaler”, was notified during ongoing discussions that the City was updating its UWMP in March 2026 and again on May 9, 2026.

Integrated Regional Water Management Group
The County has developed an Integrated Regional Water Management Plan which included involvement and participation by the City as well as other agencies and interested individuals throughout the County, collectively referred to as the Integrated Regional Water Management Group. The County was notified during ongoing discussions that the City was updating its UWMP in March of 2026 and again on May 9, 2026.

2.2 Public Participation and Plan Adoption
The City encouraged public participation during preparation of the 2025 UWMP through public noticing, availability of the draft plan for review, and a City Council public hearing. The public review, hearing, adoption, and post-adoption submittal process is described in Chapter 10.

2.3 Plan Implementation
The City prepared the 2025 UWMP on a fiscal-year reporting basis. For purposes of this UWMP, the 2025 reporting year generally corresponds to Fiscal Year 2024–25 (July 1, 2024 – June 30, 2025) with all fiscal year periods running from July 1 through June 30. Implementation of the UWMP is the responsibility of the City’s Public Works and Utilities Department, Utilities Branch. A detailed discussion of plan implementation requirements is provided in Chapter 10.

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2025 Urban Water Management Plan
15 2.4 Standardized Tables
Per the requirements of the CWC, standardized tables for the reporting and submittal of the UWMP data were developed and are required to be published in this report. The standardization of data tables allows for efficient data management, expedited review of UWMPs, and compilation of data for regional and statewide planning. The City will submit UWMP and WSCP data electronically to DWR using standardized tables and have included the standardized tables within Appendix A.

2.5 Compliance Checklist
The City completed the checklist of specific 2025 UWMP requirements and included it in the Plan as Appendix B, consistent with DWR guidance. The Checklist includes each 2025 UWMP requirement by subject, applicable CWC section, and the page number where the required element is addressed in the Plan. This checklist serves to assist in the DWR review of the City’s 2025 UWMP.

CHAPTER 3: SERVICE AREA DESCRIPTION

3.1 Introduction
This chapter provides an overview of the City of San Luis Obispo’s water service area, demographic characteristics, land use conditions, and other planning assumptions used in development of the 2025 UWMP. Information contained in this chapter establishes the basis for the City’s current and projected water demand analysis, water supply reliability evaluation, and long-term water resources planning efforts described in subsequent chapters of the UWMP.

The City of San Luis Obispo is located in central San Luis Obispo County along California’s Central Coast and serves as a regional center for residential, commercial, educational, governmental, and recreational activities. The City provides potable water service within the city limits through a municipally owned and operated water system consisting of water supply, treatment, storage, transmission, and distribution infrastructure. The City also delivers recycled water for non-potable use in designated service areas.

The City’s water system is supported by a diversified water supply portfolio consisting primarily of surface water and recycled water resources, with a project currently under construction to bring groundwater supplies online as an additional drinking water source. Long-term water supply planning for the City is influenced by a variety of factors, including population growth, land use planning, water use efficiency requirements, hydrologic variability, regulatory conditions, infrastructure needs, and climate-related uncertainties. Accordingly, this chapter describes the physical, demographic, and planning characteristics of the community that support the water demand
and water supply analyses contained in this
UWMP.

The UWMP Act requires urban water suppliers to
evaluate current and projected water demands
over a minimum twenty-year planning horizon.

Consistent with these requirements, the City’s
2025 UWMP evaluates water demand and
supply reliability conditions through the year 2045
and includes additional planning projections
through 2050, as recommended by DWR, using
the best available demographic, land use, and
planning information available at the time the
UWMP was prepared.

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2025 Urban Water Management Plan
16 3.2 Service Area Overview
The City of San Luis Obispo is located approximately halfway between Los Angeles and San Francisco along California’s Central Coast. The City encompasses approximately 13.2 square miles, of which approximately 13.0 square miles is land and approximately 0.18 square miles is water.

The City serves as the primary urban center within San Luis Obispo County and includes a mix of residential, commercial, institutional, governmental, educational, and recreational land uses. Major institutional and community features within or directly adjacent to the City include Cal Poly, Cuesta College, the downtown commercial core, regional medical facilities, and various public and recreational facilities serving both residents and visitors.

The City is the sole provider of potable water service within the city limits and maintains water supply, treatment, transmission, storage, and distribution infrastructure necessary to support existing and future water demands. In addition to potable water service, the City operates a recycled water system serving designated non-potable reuse areas.

3.3 Climate and Hydrologic Conditions
The City is situated within a coastal valley
approximately ten miles inland from the Pacific
Ocean and experiences a Mediterranean climate
characterized by mild, dry summers and cool,
moderately wet winters. Average annual precipitation
within the City is approximately 23 inches, with the
majority of rainfall occurring between November and
April. Summer conditions are generally warm and
sunny, often influenced by marine fog and coastal
weather patterns. Winter temperatures are typically
mild, although periodic freezing temperatures may
occur during colder weather events.

The City’s climate and seasonal weather patterns
influence both water demands and available water
supplies. Irrigation demands generally increase
during the dry summer months when
evapotranspiration rates are highest and precipitation
is limited. However, compared to many inland
California communities, the City experiences less
extreme seasonal water demand variation due to its
moderate coastal climate, long-standing community
emphasis on water conservation and water-efficient
landscaping, and the influence of Cal Poly on water
use, where student populations have historically
declined during summer months when many students
leave the area while irrigation demands are typically
at their highest. Table 3-1 summarizes monthly
evapotranspiration, precipitation, and average
temperature data for the City.

Although the City itself experiences relatively
moderate coastal climate conditions, the watersheds supplying the City’s surface water reservoirs are located in areas with differing climatic and hydrologic characteristics. The City’s water supply portfolio includes reservoirs located both closer to the coast and farther inland, where temperatures, precipitation patterns, evapotranspiration rates, and hydrologic conditions may vary significantly from those experienced within the City. As a result, hydrologic conditions affecting reservoir storage, watershed runoff, and water TABLE 3-1: SAN LUIS OBISPO CLIMATE
ETo
(in)
Average
rainfall
(in)
Average
temperature
(F)
January 2.77 5.53 52.3
February 2.72 3.63 55.6
March 3.58 4.99 53.7
April 4.41 0.84 55.6
May 5.86 0.19 58.7
June 5.94 0.07 59.7
July 6.01 0.02 61.1
August 6.14 0.00 64.6
September 4.19 0.31 65.8
October 4.10 0.41 61.6
November 2.44 1.25 58.7
December 2.64 5.49 59.2
Annual 50.80 22.73 58.9
Source:

1. Evapotranspiration (ETo) from: California Irrigation Management Information System (CIMIS) Station 52,
January 2025 - December 2025.

2. Average rainfall data for 2020-21 through 2024-25:
https://www.slocounty.ca.gov/departments/publicworks/forms-documents/water-resources/monthlyprecipitation-reports/slo-reservoir-precipitation-datasite-749

3. Average Temperature from: California Irrigation
Management Information System (CIMIS) Station 52,
January 2025 - December 2025.

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2025 Urban Water Management Plan
17 supply availability may not directly correlate with weather conditions observed within the City itself.

Because the City relies primarily on surface water supplies obtained from multiple watersheds, hydrologic conditions and climate data associated with those watersheds are incorporated into the City’s water supply planning and water management models. Variability in rainfall, runoff, reservoir inflows, and watershed conditions can differ significantly between watersheds and may substantially influence long-term water supply availability and reliability.

3.4 Water System Overview
The City operates a municipally owned and operated potable water system that includes water supply, treatment, transmission, storage, pumping, and distribution infrastructure necessary to provide reliable water service to the community. The City’s water system has been developed over many decades and includes multiple water supply sources, regional conveyance facilities, water treatment infrastructure, and an interconnected distribution system designed to support both domestic water use and fire protection demands.

3.4.1 Water Supply Sources
The City utilizes three surface water
reservoirs to meet potable water
demands. Salinas Reservoir, located
southeast of the community of Santa
Margarita, has provided water to the City
since 1944. Whale Rock Reservoir,
located near the community of Cayucos,
has served as a City water source since
1961. Deliveries from Nacimiento
Reservoir to the City began in 2011
following completion of the Nacimiento
Water Project. Collectively, these
supplies provide the foundation of the
City’s long-term potable water supply
portfolio.

Raw water from each reservoir is
conveyed to the City’s Water Treatment
Plant (WTP) through three separate
transmission systems. The City’s
diversified surface water portfolio
provides operational flexibility and helps
reduce dependence on any single water
source or watershed.

The City does not currently rely on local
groundwater to meet normal potable
water demands; however, groundwater
was used extensively during previous
drought conditions and is planned to return to service beginning in FY 2027-28 through development of new groundwater production wells and treatment facilities. In addition to potable supplies, the City also produces recycled water at the Water Resource Recovery Facility (WRRF) for landscape irrigation, construction-related activities, and other approved non-potable uses. In 2025, the City completed upgrades to the WRRF intended to improve recycled water quality, maximize recycled water production, and allow for the increased utilization of recycled water resources in the future.

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2025 Urban Water Management Plan
18 3.4.2 Water Treatment Facilities
The City’s Water Treatment Plant (WTP) is located on Stenner Creek Road, northwest of the Cal Poly campus. The facility was constructed in 1964 to provide treatment of surface water from Salinas and Whale Rock Reservoirs. The WTP is a conventional plant that includes ozone disinfection, coagulation, flocculation, sedimentation, and filtration. The WTP was originally designed to treat up to eight million gallons per day (mgd). In 1977, the plant was upgraded to provide 11.5 mgd of treatment capacity but actually treated up to 12 mgd for limited periods during peak summertime water demands.

Since the WTP was constructed, drinking water treatment regulations have become increasingly protective of public health. The Safe Drinking Water Act (SDWA), adopted in 1974 and significantly amended in 1986, established the national framework for regulating public drinking water systems. Following the 1986 amendments, the U.S. Environmental Protection Agency (EPA) adopted several major rules affecting surface water treatment, including the Surface Water Treatment Rule, which established treatment requirements for surface water supplies to reduce the risk of waterborne disease. In 1994, the City completed a major WTP upgrade to comply with new regulatory requirements and to convert the WTP’s primary disinfectant to ozone. Ozone provides a high level of disinfection for surface water supplies, reduces the need to rely on chlorine for primary disinfection, and helps reduce the formation of trihalomethanes (THMs), also referred to as total trihalomethanes (TTHMs) when measured as a regulated group. The use of ozone also helps address taste and odor issues associated with source water conditions such as algae blooms at Salinas Reservoir. Even after the installation of ozone is the WTP’s primary disinfectant, chlorine continues to be added after filtration to maintain a disinfectant residual in the water distribution system.

An upgrade completed in 2008 added additional onsite storage facilities, replaced an existing on-site pump station, and replaced the WTP’s sedimentation basin with a new ballasted flocculation process, known as Actiflo. The addition of the Actiflo process increased sedimentation capacity from eight mgd to 16 mgd, improving the WTP’s ability to reliably meet expected future water demand.

Although the City’s treatment process helps reduce the formation of TTHMs, disinfection byproducts can continue to form after treated water enters the distribution system. TTHM levels are influenced by factors such as water temperature, natural organic matter, chlorine residual, and water age. Higher TTHM levels can occur where water age is greater, often resulting from oversized storage tanks with lower turnover or limited mixing. During recent drought periods, reduced water use and increased conservation contributed to lower turnover in some storage facilities, which increased the need for additional distribution system water quality improvements.

To address these conditions, the City has completed several projects to improve treated water storage and distribution system water quality. In 2020, mixing, aeration, and ventilation equipment was installed at Clearwell 2 at the WTP and at Edna Saddle Tank in the distribution system. Additional projects completed in 2021 and 2024 added tank mixing, chlorine analyzers, and automated chlorine dosing at Reservoir 1 and Reservoir 2, the City’s two largest treated water storage tanks. These improvements support more consistent disinfectant residual management, reduce water age impacts, and help the City maintain compliance with drinking water regulations while continuing to provide high-quality water to customers.

Also in 2020, the City entered into a public/private partnership with Pacific Gas and Electric (PG&E) for the Water Energy Efficiency Project at the WTP. Project components included upgrading the ozone generation system, SCADA system, plant service water system, and improvements to the Transfer Pump Station. It is estimated that implementation of the Water Energy Efficiency Project will result in a reduction of energy usage of roughly 33 percent when compared to 2019 WTP operations.

Following the initiation of the partnership with PG&E, the City received grants to support the installation of a diesel-powered backup generator that allows the WTP to operate during power outages. This generator was supplemented by the installation of a Tesla backup battery that allows the WTP to reduce electrical demand during peak energy pricing periods and power the plant for up to ten hours during a short-duration power outage. These two assets allow the City to continue treating and delivering water during power

DRAFT
2025 Urban Water Management Plan
19 outages, which have increased in frequency and duration following significant wildfires across the State.

3.4.3 Potable Water Distribution System
The City’s potable water distribution system conveys treated water from the WTP to approximately 17,500 service connections and more than 2,000 public fire hydrants. The system includes approximately 190 miles of water mains, eight treated water storage facilities, and seven pump stations.

The distribution system is divided into two primary networks: a high-pressure system and a low-pressure system. These systems largely operate independently from one another due to the City’s varied topography.

Water serving the higher elevation portions of the City is pumped from the WTP through the Transfer Pump Station into the high-pressure zones. The high-pressure system serves the Cal Poly campus and portions of the City generally located north and east of the Union Pacific Railroad tracks. Water serving lower elevation areas flows by gravity from the WTP Clearwell storage facilities into the lower-pressure service zones.

To accommodate the City’s topography and service area elevations, the distribution system is further divided into 11 pressure zones. These zones are designed to maintain system pressures generally between 40 and 80 pounds per square inch (psi) under normal operating conditions. Maintaining appropriate pressure is important for protecting distribution system water quality, supporting domestic water use, meeting fire protection needs, and reducing water loss that can occur when pressures are excessive.

Treated water storage is a key component of the City’s distribution system. Storage facilities provide operational flexibility, stabilize pressure, support emergency response, and provide fire flow capacity. The City’s treated water storage system includes five steel tanks and three concrete storage facilities with a combined storage capacity of more than 25 million gallons.

The City’s potable water system also includes transmission and distribution mains constructed from a variety of pipe materials, including cast iron, ductile iron, asbestos cement, polyvinyl chloride (PVC), copper, polyethylene, and other materials installed during different periods of system development. Portions of the distribution system are approaching or have exceeded their anticipated service life. As a result, ongoing maintenance, rehabilitation, and replacement are necessary to maintain system reliability, minimize service disruptions, and reduce water loss. Pipeline replacements are prioritized through implementation of the City’s Potable Water Distribution System Operations Master Plan.

The distribution system also supports fire protection through a network of more than 2,000 public hydrants and approximately 200 private hydrants located throughout the community. Hydrant maintenance, testing, and replacement activities are performed regularly by Utilities Branch staff to maintain fire flow reliability and operational readiness.

The City implements preventative maintenance programs throughout the distribution system to support long-term reliability and operational performance. These programs include water main maintenance and repair, pump station maintenance, storage facility inspection and maintenance, valve exercising, pressure reducing valve maintenance, hydrant testing and maintenance, cross-connection control program management, and distribution system water quality monitoring and sampling.

The City currently uses a contract service provider for meter reading operations to support standardized billing periods. In recent years, the City has begun implementing an Advanced Metering Infrastructure (AMI) system to improve water use monitoring, support conservation efforts, enhance water loss management, and provide customers with better access to water use information. As of 2025, approximately 5,000 meters had been equipped with radio communication endpoints as part of a phased transition to a full AMI system anticipated to be completed in 2028. Once complete, the AMI system is expected to provide more timely and detailed water use data, improve leak detection capabilities, reduce inefficiencies associated with manual meter reading, and support long-term water management and conservation planning. AMI will also improve the City’s ability to monitor customer water use and support implementation of the Water Shortage

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2025 Urban Water Management Plan
20 Contingency Plan during water shortage emergencies.

3.4.4 Recycled Water System
The City of San Luis Obispo operates a recycled water system utilizing disinfected tertiary-treated effluent produced at the City’s WRRF. The recycled water system was developed as part of the City’s long-term strategy to maximize beneficial reuse of available water resources, reduce potable water demands where feasible, and improve overall water supply resiliency. The City’s recycled water program operates in accordance with applicable State regulations governing recycled water use, including Title 22 of the California Code of Regulations and requirements established by the Regional Water Quality Control Board (RWQCB).

The City’s WRRF is located on Prado Road in the southern portion of the City and serves residential, commercial, industrial, institutional, and governmental wastewater customers within the community, including Cal Poly and the County Regional Airport. The WRRF provides tertiary treatment prior to discharge or reuse and has undergone multiple upgrades intended to improve treatment reliability, regulatory compliance, and recycled water production capabilities.

The City’s Water Reuse Project, completed in 2006, included improvements to the WRRF and construction of approximately eight miles of recycled water distribution pipeline. The recycled water system includes a dedicated recycled water pump station and storage tank located at the WRRF. The distribution system primarily serves landscape irrigation demands at parks, schools, roadway medians, common areas, Caltrans facilities, Laguna Lake Golf Course, and other approved non-potable reuse sites throughout the southern portions of the City. The City also operates a construction water permit program that allows recycled water to be utilized for dust control and compaction activities at approved construction sites.

The City’s recycled water system was designed to allow for future expansion as additional recycled water demands are identified. In addition to existing recycled water use, the City has evaluated opportunities for future recycled water system expansion and potential future potable reuse applications through development of the City’s Recycled Water Master Plan and related planning studies.

The City’s recycled water supply varies seasonally based on wastewater generation, irrigation demand, storm-related inflow and infiltration, treatment plant operations, and other operational considerations. The City is also required to discharge approximately 1.6 million gallons per day of treated wastewater effluent to San Luis Obispo Creek to maintain minimum flows for downstream aquatic habitat. Because this environmental discharge requirement represents a fixed daily commitment, the volume of recycled water available for customer use depends on the amount of treated effluent remaining after this requirement is met.

3.5 Existing Population and Demographic Characteristics The City of San Luis Obispo was founded in 1772 and incorporated in 1856, making it one of California’s oldest communities. Today, the City serves as the civic, economic, educational, and cultural center of San Luis Obispo County. The City supports a diverse mix of residential, commercial, governmental, educational, healthcare, and recreational land uses that contribute to both resident and regional water demands.

The City’s estimated 2025 population was 49,849, according to California Department of Finance estimates 1. Based on these estimates, between 2021 and 2025, the City’s population increased by approximately 2,449 people, which is generally consistent with the one percent growth assumptions established in the City’s General Plan. Future growth within the City is anticipated to occur within the Margarita, Orcutt, Airport Area, and Froom Ranch Specific Plan areas, as well as through infill development and intensification of existing developed areas including portions of the downtown core and other mixed1 Population estimates for the City of San Luis Obispo are available at the California Department of Finance website at: https://dof.ca.gov/media/docs/forecasting/Demographics/estimates/e-4-population-estimates-for-cities-countiesand-the-state-2021-2026-with-2020-census-benchmark/E-4_2026_InternetVersion.xlsx

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2025 Urban Water Management Plan
21 use areas.

The City’s age demographics are relatively well
distributed. According to Regional Economic Action
Coalition demographic information for 2025 (Applied
Geographic Solutions, June 2025), approximately 22
percent of the population is under the age of 20, 21
percent is between the ages of 20 and 24, 23 percent is between the ages of 25 and 44, 17 percent is between the ages of 45 and 64, and 17 percent is 65 years of age or older2.

The City is the cultural hub of the Central Coast with a daytime population of up to 90,000 people, nearly double its permanent population. With major regional employers located within or adjacent to City limits, the City is not only the cultural hub but also the civic and economic hub in the region. Public sector jobs account for a sizeable portion of the job market in the City. Service and retail jobs also comprise a large percentage of employers. The City’s median household income was $73,685 (in 2024 dollars3), up from $56,071 in 2019. The City's 2025 Annual Comprehensive Financial Report documents the top employers within and adjacent to the City, as shown in Table 3-2.

TABLE 3-2: TOP EMPLOYERS
# Employer # of Employees
1 California Polytechnic State University (Cal Poly) 3,177 2 County of San Luis Obispo 2,956
3 Cal Poly Corporation (Foundation) 2,787
4 Pacific Gas & Electric Company (PG&E) 1,824
5 California Men’s Colony 1,350
6 San Luis Coastal Unified School District 1,070
7 Sierra Vista Regional Medical Center 779
8 Cuesta Community College 773
9 French Hospital Medical Center 688
10 City of San Luis Obispo 654
Source: City of San Luis Obispo 2025 Annual Comprehensive Financial Report (Schedule 21 – Principal Employers)

3.6 Future Population Projections
The City’s General Plan Land Use Element (LUE), Housing Element, and WWE provide important planning assumptions related to future population growth, land use, housing, and water demand. For purposes of the 2025 UWMP, the City uses the population growth methodology outlined in the General Plan LUE as the basis for long-term water demand forecasting.

The General Plan LUE establishes a residential growth management framework under which the City manages growth of the housing supply so that it does not exceed one percent per year on average, subject to specific exclusions and implementation provisions. The LUE includes projected population assumptions 2 https://reachcentralcoast.org/demographics/
3 https://www.census.gov/quickfacts/fact/dashboard/sanluisobispocitycalifornia/PST045219

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2025 Urban Water Management Plan
22 through 2035 and identifies an estimated urban reserve capacity of approximately 57,200 persons. For UWMP demand-planning purposes, the City uses the General Plan population growth framework through 2035 and extends the one-percent annual growth methodology through 2050 to evaluate long-term water supply and demand reliability.

Use of the General Plan growth methodology provides a conservative basis for water supply planning because actual population growth has generally occurred at a slower rate than the maximum growth assumptions identified in the General Plan LUE.
4 This approach is intended to ensure that the UWMP
evaluates water supply reliability under a planning scenario that is consistent with adopted City land use policy and sufficiently conservative for long-term water supply planning.

Table 3-3 summarizes the City’s estimated current 2025 population, the LUE population planning assumptions through 2035, and the UWMP’s demand-planning population projections through 2050 based on extending the General Plan’s one-percent annual growth methodology beyond 2035.

TABLE 3-3: CITY POPULATION PROJECTIONS
2025 2030 2035 2040 2045 2050
Census-based City Population
(2025)1 49,849 - - - - -
General Plan LUE Projected
Population2 51,317 53,934 57,200 - - -
Projected Population Assuming
One Percent Annual Growth
Beyond 2035 LUE Projections3
- - - 60,118 63,184 66,407
Notes:

1. 2025 population estimate for the City of San Luis Obispo is from the California Department of Finance website at: https://dof.ca.gov/forecasting/demographics/estimates-e1/

2. 2025, 2030 and 2035 population planning assumptions are based on City of San Luis Obispo, General Plan, LUE, Table 3.

3. 2040, 2045, and 2050 population planning assumptions extend the General Plan’s onepercent annual growth methodology beyond 2035 for UWMP water demand-planning purposes.

Population projections and future water demand assumptions utilized within this UWMP are intended solely for purposes of evaluating long-term water supply reliability, infrastructure planning, drought preparedness, and compliance with the Urban Water Management Planning Act. Nothing within this UWMP establishes land use entitlements, approves future development projects, or modifies the City’s adopted General Plan land use designations, growth management policies, or development review procedures.

3.7 Land Use Characteristics and Planning Assumptions
The City’s land use planning framework is established through the City’s General Plan LUE and WWE, which together guide future growth, infrastructure planning, resource management, and long-term service planning within the community. The General Plan establishes a planning framework intended to preserve the City’s compact urban form, maintain separation between urban development and surrounding open space and agricultural lands, and support sustainable growth patterns consistent with community values and available infrastructure capacity.

The General Plan emphasizes a development pattern focused on infill development, redevelopment, mixeduse activity centers, and planned expansion within identified Specific Plan, special focus, and expansion areas rather than broad outward expansion of the City’s urban footprint. Future residential, commercial, 4 2025 State Department of Finance estimated population of 49,849 versus Land Use Element 2025 estimate of 51,317.

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2025 Urban Water Management Plan
23 mixed-use, and institutional growth is anticipated to occur primarily within the Margarita Area, Orcutt Area, Airport Area, Avila Ranch, Froom Ranch, and other identified Specific Plan and Special Focus Areas, as well as through intensification of existing developed areas, including portions of the downtown core and established commercial corridors.

The City’s planning framework places significant emphasis on preservation of open space, agricultural resources, hillsides, creek corridors, habitat areas, and other environmental resources surrounding the City.

The General Plan identifies the importance of maintaining a clear boundary between urban development and surrounding open space while encouraging a compact urban form and efficient use of existing infrastructure and public services.

Land use planning assumptions utilized in the
2025 UWMP are intended to remain generally
consistent with the City’s General Plan and
related planning documents. For purposes of this
UWMP, these assumptions provide a planning
basis for evaluating future water demands,
infrastructure needs, and long-term water supply
reliability. Actual development timing, location,
and intensity may vary over time based on market
conditions, project approvals, infrastructure
sequencing, housing production, regional growth
trends, and other factors.

The City’s land use and infrastructure planning
efforts are also influenced by sustainability and
climate-related planning objectives contained within the General Plan. These objectives include encouraging sustainable infrastructure, reducing greenhouse gas emissions, supporting alternative transportation modes, improving energy efficiency, protecting natural resources, reducing the jobs/housing ratio, and fostering resilient long-term community development patterns.

The City implements and enforces water-efficient development requirements consistent with applicable State regulations and local policies, including the State Model Water Efficient Landscape Ordinance (MWELO), California Green Building Standards Code (CALGreen), low impact development requirements, non-functional turf prohibitions and reductions, and other water conservation-related development standards. These requirements are intended to improve long-term water use efficiency, reduce irrigation demands, encourage sustainable landscape practices, and support the City’s long-term water supply reliability objectives. Modern water efficiency standards also allow the City to develop more refined longterm water demand projections by better reflecting the reduced indoor and outdoor water use characteristics of contemporary development compared to historical development that occurred before current water efficiency requirements.

CHAPTER 4: WATER USE CHARACTERIZATION

4.1 Introduction
This chapter describes the City’s historical potable water demands, current water use characteristics, and projected future water demands through the UWMP planning horizon (2025-2050). The City’s potable water demands are influenced by a variety of factors including population growth, land use patterns, climate conditions, conservation practices, economic activity, seasonal irrigation demands, and water-efficient development standards.

Water demand projections developed in this chapter are used to evaluate future water supply reliability, drought preparedness, infrastructure planning, and compliance with the UWMP Act.

DRAFT
2025 Urban Water Management Plan
24 This chapter also summarizes the City’s water loss auditing program, gross water use calculations, and per capita water use metrics utilized for compliance with SWRCB requirements.

4.2 Demand Sector Definitions
Potable water demand in the City is comprised of several sectors5, consisting of the following:
• Single-family Residential: A single-family dwelling unit. A lot with a free-standing building containing one dwelling unit that may include an attached or detached accessory dwelling unit (ADU) or Junior ADU.
• Multi-family Residential: Multiple dwelling units contained within one building or several buildings within one complex.
• Landscape: Water connections supplying water solely for landscape irrigation. Such landscapes may be associated with multi-family, commercial, industrial, or institutional/government sites, but are considered a separate water use sector if the connection is solely for landscape irrigation.
• Commercial: A water user that provides or distributes a product or service. • Industrial: A water user that is primarily a manufacturer or processor of materials as defined by the North American Industry Classifications System (NAICS) code sectors 31 to 33, inclusive, or an entity that is a water user primarily engaged in research and development.
• Institutional: A water user dedicated to public service. This type of user includes, among other users, higher education institutions, schools, courts, churches, hospitals, government facilities, and nonprofit research institutions.
• Distribution System Losses: Examples of system losses are provided in • Table 4-4: Common Water Loss & Unbilled Consumption Types4.

4.3 Historical Water Demand
Historically, the City experienced high per capita potable water demands leading into the drought of the late 1980s and early 1990s. During this severe drought, the City implemented strict water conservation measures intended to reduce potable water demand to preserve limited available water supplies. These measures included mandatory conservation requirements, restrictions on outdoor irrigation, a set allotment of water based on business type (for commercial properties) and number of residents (for residential 5 The City compiles commercial, industrial, and institutional accounts in one category known as “CII” consistent with CWC 10608.12.

Examples of Water Loss & Unbilled Authorized Consumption Causes Water Loss Mainline & Service Line
Leakage Meter Inaccuracies Data Handling Errors
Overflow of
Storage Tanks
Unbilled
Authorized
Consumption
Treatment Plant and
Distribution System
Process Water
Mainline Flushing Fire Flow Testing Water Quality
Testing

DRAFT
2025 Urban Water Management Plan
25 properties), and other demand reduction strategies. Although these efforts resulted in substantial reductions in potable water use, much of the reduction observed during that period was associated with temporary behavioral changes in response to drought conditions and City regulations, rather than long-term permanent reductions in baseline water demand.

As drought conditions improved during the 1990s, potable water demand gradually increased again through the late 1990s, where water demand ultimately plateaued from around 1997 through 2009. Around 2009- 2010 the City implemented significant water rate increases associated with construction and operation of the Nacimiento Water Project at which point water demand again began to decrease leading into the 2012- 2015 drought period. The reduction of potable water demand became more pronounced during the 2012– 2015 drought and subsequent State and local drought response regulations. During the latter years of the drought, the City implemented significant conservation measures and water use reduction requirements consistent with statewide drought response efforts. Unlike prior drought periods, reductions in potable water demand observed during and after the 2012–2015 drought appear to have been more permanent in nature.

Since approximately 2010, and particularly following the 2012–2015 drought, the City’s total potable water demand has generally leveled off and has not increased at a rate directly proportional to population growth.

Although the City has continued to experience population growth over this period, increases in water demand attributable to additional population have largely been offset by ongoing improvements in water use efficiency within the City’s existing customer base. These improvements include installation of low-flow plumbing fixtures and appliances, increased use of water-efficient landscaping and irrigation systems, updated building and landscape development standards, implementation of water conservation programs, and lasting changes in customer water use behavior. As a result, both per capita and overall potable water demand have remained comparatively low and stable relative to historical pre-drought conditions.

Over the past 30 years, from 1996 through 2025, annual potable water demand in the City has ranged from a high of 6,416 acre-feet in 2007 to a low of 4,520 acre-feet in 2016, a difference of more than 1,895 acrefeet. In contrast, over the most recent ten-year period from 2016 through 2025, annual potable water demand has ranged from a high of 5,019 acre-feet to a low of 4,520 acre-feet, a difference of approximately 499 acre-feet. This substantially narrower range in annual demand indicates that post-drought potable water use has become more stable and less variable than historical pre-drought demand conditions. The reduced variability in water demand also suggests that a significant portion of the conservation achieved during and following the 2012–2015 drought represents lasting efficiency improvements and permanent changes in water use behavior rather than temporary drought-response reductions alone. As a result, future drought-related conservation measures may yield smaller reductions in overall potable water demand than were achieved during previous drought periods when baseline water use levels were substantially higher.

4.4 Current Water Demand
Current potable water demand within the City is primarily comprised of residential, commercial, institutional, industrial, irrigation, and distribution system water loss sectors. As shown in Table 4-1: 2025 Potable Water Use by Sector, single-family residential demand represents the largest individual water use sector within the City, accounting for approximately 40 percent of total potable water demand in 2025. Commercial, industrial, and institutional uses collectively account for approximately 23 percent of total demand, while multi-family residential demand represents approximately 24 percent of total potable water demand.

Dedicated landscape irrigation accounts for approximately 11 percent of total potable water demand.

Distribution system water loss accounted for approximately 7 percent of total potable water demand in 2025. Water loss includes both real losses, such as leakage from pipelines and appurtenances, and apparent losses associated with meter inaccuracies or data handling issues. Additional discussion regarding the City’s water loss auditing program and distribution system losses is provided in Section 4.6 of this chapter.

TABLE 4-1: 2025 POTABLE WATER USE BY SECTOR

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2025 Urban Water Management Plan
26 2025 Potable Water Use Sector
SingleFamilyMultifamily
Commercial,
Industrial,
and Institutional
Dedicated
Irrigation
Distribution System
Water Loss
Total
Volume
Water Use (AFY) 1,917 1,193 1,033 306 384 4,833
% of 2025 total: 40% 25% 21% 6% 8% 100%
Source: City of San Luis Obispo Utilities Department, 2026.

4.5 Future Water Demand Projections
Future potable and non-potable water demand projections were developed for the 2025 UWMP planning horizon to support long-term water supply reliability analysis, infrastructure planning, drought preparedness, and compliance with the UWMP Act. The demand projections presented in this section are used for longterm planning purposes and are intended to evaluate whether the City’s existing and planned supplies are sufficient to meet projected demands through 2050.

Future potable water demand projections were developed using the population methodology described in Section 3.6 and the City’s long-term potable water demand planning value of 117 gallons per capita per day (gpcd). This approach is consistent with the General Plan and WWE and provides a conservative basis for evaluating long-term water supply reliability. The 117 gpcd planning value is based on the City’s confirmed SB X7-7 water use target and is higher than the City’s current estimated potable water use of 87 gpcd. Use of the higher 117 gpcd value provides a buffer for potential changes in future water use patterns, land use, climate, hydrologic conditions, regulations, customer behavior, and other factors that may affect demand over the multi-decade UWMP planning horizon.

The City’s long-term potable water demand projections are based on the population methodology described in Section 3.6 and the City’s 117 gpcd water demand planning value. The projections are not reduced further to separately quantify future water savings from plumbing codes, appliance standards, building standards, landscape ordinances, transportation plans, or other adopted conservation-related policies. This approach is conservative because the 117 gpcd planning value is higher than current estimated potable water use and does not assume additional future demand reductions beyond those already reflected in existing customer water use patterns and the City’s long-term planning methodology. Applicable codes, standards, ordinances, and plans that support ongoing water use efficiency include the California Plumbing Code, California Green Building Standards Code, the Model Water Efficient Landscape Ordinance and City landscape requirements, the City’s water waste prevention provisions, and the General Plan and WWE.

The long-term demand projections shown in this section are not intended to represent expected customer water use during upcoming single-year assessment periods or the five-year drought risk assessment outlined in this UWMP. Near-term operational reliability analyses are conducted for a different purpose and use more current information, including recent actual water use, current population estimates, recent seasonal demand patterns, dry-year adjustments, source availability, and known or anticipated infrastructure constraints. These assumptions inform the City’s Water Projection Model, which is used to assess near-term water supply availability and evaluate whether actual or anticipated conditions may result in a shortage. This distinction is important as it allows the City to preserve a conservative long-term demand forecast for General Plan consistency and multi-decade planning, while using more precise near-term information when evaluating actual or anticipated shortage conditions.

The City’s projected water demands include anticipated residential and non-residential growth within the City’s urban services area, including projected water use associated with lower-income housing identified in the City’s Housing Element. California Water Code Section 10631.1(a) requires urban water suppliers to include projected water use for single-family and multifamily residential housing needed for lower-income households, as identified in the housing element of any city, county, or city and county within the supplier’s

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2025 Urban Water Management Plan
27 service area. The City’s adopted Housing Element identifies the City’s 6th Cycle Regional Housing Needs Allocation, including 825 very-low-income (inclusive of 412 extremely-low-income) units and 520 lowincome units, for a total of 1,345 lower-income housing units. For informational purposes and consistency with California Water Code Section 10631.1(a), the estimated water demand associated with lower-income housing is approximately 430 acre-feet per year.6
Because the City’s water demand projections are based on projected population within the planning timeframe through 2050, water demand associated with lower-income housing is included within the City’s overall water demand forecast. The estimated annual 430 acre-feet of water demand for lower-income residential units is included in single and multi-family residential water demand estimates presented in Table 4-2: Projected Future Potable Water Demand by Year below. This estimate demonstrates the scale of projected water use associated with lower-income housing and confirms that such demand is included within the City’s overall projected residential water demand.

Projected future potable water demand by sector is presented in Table 4-2: Projected Future Potable Water Demand by Year below, with non-potable water demand shown separately in Table 4-3: Projected Future Non-Potable Water Demand by Sector.

TABLE 4-2: PROJECTED FUTURE POTABLE WATER DEMAND BY YEAR Potable Water Demand (Acre-Feet) by Year
2030 2035 2040 2045 2050
Single Family 2,804 2,973 3,125 3,285 3,452
Multi-Family 1,744 1,850 1,944 2,043 2,148
Dedicated Irrigation
/ Landscape 447 474 498 523 550
Commercial 1,381 1,464 1,539 1,617 1,700
Institutional 84 89 93 98 103
Industrial 47 50 52 55 58
Distribution System
Water Loss 562 596 627 659 692
Total Potable
Water Demand 7,068 7,496 7,879 8,281 8,703
Notes: Individual demand categories are displayed as whole numbers for readability; however, underlying calculations are performed using values carried to additional decimal places. As a result, totals may not equal the exact sum of the displayed values due to rounding.

TABLE 4-3: PROJECTED FUTURE NON-POTABLE WATER DEMAND BY SECTOR Non-Potable Water Demand (Acre-Feet) by Year
2030 2035 2040 2045 2050
Landscape 293 343 393 443 493
Golf Course 33 33 33 33 33
6 Estimated water demand is based on 1,345 lower-income housing units, an average household size of 2.44 persons per household, and the City’s conservative long-term planning assumption of 117 gallons per capita per day.

DRAFT
2025 Urban Water Management Plan
28 Construction Water
Program Use 12 12 12 12 12
Water/Sewer Utility
Use 0.02 0.02 0.02 0.02 0.02
Total Non-Potable
Water Demand 338.02 388.02 438.02 488.02 538.02
Notes: Individual demand categories are displayed as whole numbers for readability; however, underlying calculations are performed using values carried to additional decimal places. As a result, totals may not equal the exact sum of the displayed values due to rounding.

4.6 Distribution System Water Loss
Senate Bill 555 (2015) requires retail water suppliers in California with more than 3,000 service connections or annual deliveries exceeding 3,000 acre-feet to complete an annual water loss audit of their distribution system. The standardized audit must be validated by a certified water loss auditor to ensure consistency and accuracy in reporting. The City submitted its first validated water loss audit to the DWR in 2017 for Calendar Year 2016 and has continued to complete annual audits thereafter.

The City performs annual water loss audits using the methodology outlined in the Water Audits and Loss Control Programs Manual (M36) published by the American Water Works Association (AWWA). Water loss audits for reporting years 2020, 2021, and 2022 were completed on a calendar-year basis. Following submittal of the calendar year 2022 audit, the City transitioned to a fiscal-year reporting basis to better align with internal financial, billing, and operational data systems. As a result of this transition, the City has included six water loss audits in this UWMP rather than five: Calendar Years 2020, 2021, and 2022, followed by Fiscal Years 2022-23, 2023-24, and 2024-25. The Calendar Year 2022 and Fiscal Year 2022-23 audits partially overlap due to the transition in reporting basis; however, including both audits provides a complete and transparent record of the City’s submitted audits and ensures continuous coverage of the applicable five-year period. Due to the change in reporting periods, there is no standalone water loss audit corresponding specifically to Calendar Year 2023. The change in reporting periods does not affect the City’s overall evaluation of system water loss trends or compliance with State reporting requirements.

The results of the annual water loss audits are submitted to the State to comply with water loss reporting requirements enacted pursuant to California Water Code Section 10631.1. In addition to the audit itself, the City reports actions taken to improve the accuracy and validity of water loss data, reduce apparent losses, and reduce real losses within the potable water distribution system.

Water losses can occur as the result of a variety of factors including, but not limited to, pipeline leaks, service line leaks, meter inaccuracies, data handling errors, and storage facility overflows. Water loss is distinct from unbilled authorized consumption, which includes approved operational uses of water that are not billed by the City, such as mainline flushing, fire flow testing, water quality sampling, and treatment process water. Losses that are neither billed nor metered are classified as apparent losses and include unauthorized consumption, metering inaccuracies, and systematic data handling errors. Common examples of water loss and unbilled authorized consumption are summarized in Table 4-4: Common Water Loss & Unbilled Consumption Types.

Examples of Water Loss & Unbilled Authorized Consumption Causes Water Loss Mainline & Service Line
Leakage Meter Inaccuracies Data Handling Errors
Overflow of
Storage Tanks
Unbilled
Authorized
Consumption
Treatment Plant and
Distribution System
Process Water
Mainline Flushing Fire Flow Testing Water Quality
Testing

DRAFT
2025 Urban Water Management Plan
29 Water loss values noted in the UWMP may vary depending on the purpose and scope of the calculation.

The validated AWWA water loss audit values shown in
Table 4-4 are used for State water loss reporting and focus on the potable distribution system. Other values presented in the UWMP may be developed for water demand, supply accounting, or operational planning purposes and may include additional volumes such as water treatment plant process water, operational uses, or losses occurring before treated water enters the distribution system. As a result, water loss values presented in different sections of this UWMP should be interpreted in the context of the specific calculation being used.

TABLE 4-4: COMMON WATER LOSS & UNBILLED CONSUMPTION TYPES The AWWA M36 methodology utilizes the Infrastructure Leakage Index (ILI) as a primary performance metric for evaluating real, or physical, water losses within a distribution system. The ILI is a unitless benchmarking metric defined as the ratio of Current Annual Real Losses (CARL) to Unavoidable Annual Real Losses (UARL). This metric allows comparison of leakage performance between water systems while accounting for differences in system size, pressure, number of service connections, and pipeline length.

Unavoidable losses represent the theoretical minimum level of leakage expected in a distribution system based on its physical characteristics and background leakage assumptions. A well-performing system generally has an ILI value below 3.0, indicating that real losses are less than three times the unavoidable leakage level, although interpretation of ILI values may vary depending on system characteristics and operating conditions. The City’s average ILI for the most recent six water loss audits is 1.8, as shown in Table 4-5: Water Loss Audit Data and Results.

TABLE 4-5: WATER LOSS AUDIT DATA AND RESULTS
Year
Billed
Authorized
Consumption
Unbilled
Authorized
Consumption
Apparent
Losses Real Losses
Infrastructure
Leakage
Index (ILI)
Real Water
Loss,
Gallon per
Connection
per Day
CY 2020 4,347.37 79.64 113.23 276.56 1.0 15.5
CY 2021 4,460.14 11.71 114.73 430.75 1.6 23.6
CY 2022 4,354.55 23.48 110.90 582.72 2.1 31.1
Examples of Water Loss & Unbilled Authorized Consumption Causes Water Loss Mainline & Service Line
Leakage Meter Inaccuracies Data Handling Errors
Overflow of
Storage Tanks
Unbilled
Authorized
Consumption
Treatment Plant and
Distribution System
Process Water
Mainline Flushing Fire Flow Testing Water Quality
Testing
Examples of Water Loss & Unbilled Authorized Consumption Causes Water Loss Mainline & Service Line
Leakage Meter Inaccuracies Data Handling Errors
Overflow of
Storage Tanks
Unbilled
Authorized
Consumption
Treatment Plant and
Distribution System
Process Water
Mainline Flushing Fire Flow Testing Water Quality
Testing

DRAFT
2025 Urban Water Management Plan
30 FY 2023 4,099.50 23.13 83.12 707.43 2.6 39.1
FY 2024 4,294.48 14.16 86.92 368.34 1.3 19.4
FY 2025 4,447.78 11.66 89.98 561.86 2.0 29.3
Six-Year Average 1.8 26.3
NOTES:

1. 2020-2022 reports utilized a calendar year reporting period. Calendar reporting year was changed to fiscal year after 2022, which results in 2024 report being next sequential reporting period after the 2022 report.

Another metric utilized to evaluate water loss performance is gallons per connection per day (gal/conn/day), which is used by the State Water Resources Control Board as a primary measure of system water loss performance. The City’s average water loss in gal/conn/day is generally comparable to values reported by other California urban water suppliers.

The State Water Resources Control Board has developed an economic model to establish system-specific water loss performance standards for each urban retail water supplier. The model estimates the level of leakage reduction that is economically feasible based on system characteristics and a lifecycle cost-benefit analysis conducted over a 30-year planning horizon. Urban water suppliers are required to comply with their assigned standards by 2028. The City’s current water loss standard is 21.0 gal/conn/day. This standard is based on the State’s economic model with an adjustment applied to account for data uncertainty and system-specific conditions using water loss audit data submitted for the period 2017 through 2020.

The City plans to continue reducing water losses and maintaining compliance with State requirements through implementation of Advanced Metering Infrastructure (AMI), improved testing and calibration of large meters, continued leak detection efforts, replacement of aging infrastructure, and ongoing system maintenance programs. Complete water loss audit reports for the five-year reporting period are provided in Appendix D.

CHAPTER 5: SB X7-7 BASELINES, 2020 TARGETS, AND 2025

REPORTING

5.1 Introduction and Regulatory Context
The Water Conservation Act of 2009 (SB X7-7) required urban retail water suppliers to establish baseline water use, adopt urban water use reduction targets, and demonstrate compliance with those targets by 2020. The legislation established a statewide goal of reducing urban per capita water use by 20 percent by 2020, along with an interim target for 2015. The City established its SB X7-7 baseline and water use targets as part of prior Urban Water Management Plans and reported compliance in the 2020 UWMP. Consistent with current UWMP requirements, this chapter summarizes the City’s previously established baseline and target values and confirms continued compliance with SB X7-7. This chapter also provides context for the transition from SB X7-7 requirements to the State’s current Urban Water Use Objective (UWUO) framework.

5.2 Baseline and Target Summary
The City established its SB X7-7 urban water use target using Target Method 3, as explained in DWR’s Methodologies for Calculating Baseline and Compliance Urban Per Capita Water Use. Under this method, the target is based on the per capita water use goal assigned to the applicable hydrologic region, and urban retail water suppliers may adopt a target equal to 95 percent of that regional value.

The City of San Luis Obispo is located within the Central Coast Hydrologic Region, which has relatively low per capita water use compared to other regions of the State due to its coastal climate and historically efficient water use patterns. Target Method 3 provides a regionally appropriate benchmark and allows for

DRAFT
2025 Urban Water Management Plan
31 consistency among suppliers within the same hydrologic region.

As documented in the City’s prior UWMPs, the City selected Target Method 3 after evaluating all stateapproved methodologies. The City determined that baseline-based methods were not appropriate due to long-standing investments in water conservation and already reduced per capita water use, which would have made additional reductions from historical baseline conditions difficult and incredibly costly to achieve.

Consistent with Water Code Section 10608.20(g) and DWR guidance, the City continues to rely on the previously established baseline and target values and has not modified its selected target method for the 2025 UWMP. The City’s baseline and target values are summarized in Table 5-1.

TABLE 5-1: SB X7-7 BASELINE AND TARGET SUMMARY
Metric Value
10-Year Baseline (1997-2006) 123 GPCD
5-Year Baseline (2004-2008) 124 GPCD
2015 Interim Target 120 GPCD
2020 Target 117 GPCD
2020 Reporting Year 94 GPCD
2025 Reporting Year 87 GPCD

5.3 SB X7-7 Compliance and 2025 Reporting
As documented in Table 5-1, the City met, exceeded, and continues to exceed its SB X7-7 water use reduction target. The adopted target of 117 gallons per capita per day (gpcd) was achieved in 2020, with an actual 2020 per capita water use of 94 gpcd. Since that time, the City has continued to maintain per capita water use below the adopted target, with its most recent data from 2025 indicating a per capita water use of 87 gpcd.

This level of performance reflects the City’s long-standing commitment to water conservation, including implementation of demand management measures, system improvements, and sustained reductions in per capita water use during and following recent drought periods. These efforts have resulted in consistently lower per capita water use, and current demand trends remain aligned with these reduced levels.

For the 2025 UWMP, the City evaluated whether any changes since the 2020 UWMP would affect its ongoing SB X7-7 compliance status. This evaluation included review of service area boundaries, population data, and water use calculation methodologies. No significant changes were identified that would require recalculation of baseline conditions or the 2020 target. Accordingly, the previously established target values remain valid for 2025 reporting purposes.

While SB X7-7 established water use reduction requirements through 2020, ongoing water use efficiency is now governed by State regulations establishing Urban Water Use Objectives (UWUO). The City will continue to monitor water use trends and implement demand management measures, as described in Chapter 9, to support long-term water use efficiency and compliance with current regulatory requirements.

Maintaining compliance with SB X7-7 and UWMP requirements is also necessary to ensure continued eligibility for State water-related grants and loans. The City’s demonstrated compliance supports continued eligibility for such funding opportunities. Supporting data for this chapter is provided in the UWMP Submittal Tables within Appendix A.

DRAFT
2025 Urban Water Management Plan
32 CHAPTER 6: NORMAL-YEAR WATER SUPPLY CHARACTERIZATION

6.1 Introduction
This chapter describes the City’s water supply portfolio and establishes the supply assumptions used to evaluate water service reliability in Chapter 7. The chapter identifies the City’s existing and planned potable and non-potable supplies, summarizes the legal, operational, and infrastructure basis for those supplies, and presents projected normal-year supply availability through the UWMP planning horizon (2025-2050).

The City’s water supply portfolio includes local surface water supplies, planned groundwater production, and recycled water. Potable supplies include Salinas Reservoir, Whale Rock Reservoir, Nacimiento Reservoir, and groundwater. Recycled water is used for approved non-potable purposes and offsets potable water demand where recycled water service is available and authorized.

The supply quantities presented in this chapter are planning values used for UWMP analysis. Actual annual use from each source may vary based on hydrologic conditions, reservoir storage, water quality, conveyance availability, treatment capacity, infrastructure conditions, regulatory requirements, seasonal demand, and operational needs. Current-year use by source may also differ from normal-year supply availability when temporary infrastructure limitations or operational constraints affect a supply, such as the recent Nacimiento transmission system outage.

The chapter also describes the City’s water supply modeling and yield assessment methods, including the combined safe annual yield analysis for Salinas and Whale Rock Reservoirs, Nacimiento Reservoir reliability considerations, planned groundwater supply assumptions, and recycled water availability. These analyses provide the basis for the projected normal-year supply volumes presented in this chapter and the normal-year, single dry-year, multiple dry-year, and drought risk assessment analyses presented in Chapter

7. 6.2 Water Supplies

6.2.1 Salinas Reservoir
Salinas Reservoir (also known as Santa Margarita Lake) is located on the upper Salinas River, approximately nine miles southeast of the community of Santa Margarita. The project was originally built by the Federal War Department to ensure an adequate water supply for Camp San Luis Obispo, as well as the City of San Luis Obispo. The dam and appurtenances were declared surplus by the War Department on April 14, 1947 and the U.S. Army Corps of Engineers assumed responsibility for the facilities. On July 11, 1947, the Corps entered into an agreement with the San Luis Obispo County Flood Control and Water Conservation District (District) for the operation and maintenance of the dam and related facilities. The City has an agreement with the Corps for use of the reservoir, as well as a water rights permit to divert water from the Salinas River for storage within the reservoir. The City is the only recipient of water stored in Salinas Reservoir.

Immediately following construction of the Salinas Dam, the reservoir had an estimated storage capacity of 24,000 acre-feet, surface area of 793 acres, and a drainage area of 112 square miles. As a result of siltation since the original construction, the reservoir capacity has been reduced to 22,508 acre-feet. A 2024 analysis conducted by the County of San Luis Obispo indicates that the siltation rate at Salinas Reservoir is approximately 46 acre-feet per year.

Salinas Reservoir
✓ Potable Water Supply
✓ Fills and Spills Frequently
✓ Exclusively Used by City of SLO

DRAFT
2025 Urban Water Management Plan
33 Operations and Distribution
Water is conveyed from Salinas Reservoir
through 9.2 miles of 24-inch diameter
reinforced concrete pipe to a three-milliongallon forebay at the Santa Margarita booster pump station near the northerly base of Cuesta
Grade adjacent to Highway 101. The pipeline
is designed to flow by gravity from the
Reservoir to the forebay when the lake level is
above the elevation of 1,267 feet. The pump
station at the base of the dam, consisting of
two horizontal centrifugal pumps, is capable of
maintaining the rated flow of 12.4 cubic feet
per second (cfs) when the water surface
elevation falls below 1,267 feet. Three
electrically driven, horizontal centrifugal
pumps at the Santa Margarita booster station
pump water through 6,810 feet of 24-inch
diameter reinforced concrete pipe to the
entrance portal of the Cuesta Tunnel, which
runs 5,327 feet through the mountains near
Cuesta Grade. From the outlet portal of the
tunnel, water is conveyed through an 18-inch diameter steel pipeline a distance of 5,133 feet to the City's turnout point. From the turnout, an 18-inch diameter pipe runs 4,180 feet to the site of Reservoir #2 on Stenner Creek Road. From there, a pipeline that varies from 24-inches to 30-inches in diameter conveys the water by gravity to the water treatment plant 5,930 feet downstream.

The operation and maintenance of the dam and water conveyance system (to the City’s turnout) are the responsibility of San Luis Obispo County Flood Control and Water Conservation District. The City pays all operating, maintenance, and capital costs associated with the reservoir and transmission system (excluding costs associated with recreational activities at the lake, which are funded by the County).

While the Salinas delivery pipeline is over 80 years old, most of the line is operated under low pressure, as the largest segment running from the reservoir to the booster pump station’s forebay is gravity fed from the reservoir. Only a small segment of pipe from the booster pump station to the Cuesta Tunnel is under pressure from an on-site pump station, however, this section opens into the Cuesta Tunnel, decreasing the risk of failure due to over pressurization or transient pressure surges. The Salinas pipeline has continually provided the City with water deliveries, with a limited number of short-duration outage periods occurring since its construction.

6.2.2 Whale Rock Reservoir
Whale Rock Reservoir is located along Old Creek approximately one-half mile east of the community of Cayucos. The project was planned, designed, and constructed under the supervision of DWR. Construction of the dam and conveyance infrastructure took place between October 1958 and April 1961. The reservoir is jointly owned by the City, the California Men's Colony, and Cal Poly who collectively form the Whale Rock Commission, which is responsible for operation and administration of the dam, reservoir, pipeline, pump stations, and associated water deliveries. Day-to-day operation of the facility is provided by the City with financial contributions towards operations and maintenance coming from all three commission member agencies. When considering storage rights and ongoing cost coverage, the City owns 55.05 percent of the water storage rights at the reservoir and is responsible for an equivalent percentage of costs. The remaining water storage rights and costs are apportioned between the two State agencies with Cal Poly owning 33.71 SALINAS DAM SPILLWAY, FEBRUARY 2019

DRAFT
2025 Urban Water Management Plan
34 percent and the California Men’s Colony owning the remaining 11.24 percent.

Operation and Distribution
Whale Rock Reservoir is formed by an earthen dam
and was able to store an estimated 40,662 acre-feet of
water at the time of construction. The dam is 266 feet
tall with a crest length of 850 feet and crest width of 30 feet. The top of dam elevation is 232.2 feet. The
Reservoir covers an area of 600 acres. The maximum
storage capacity as of 2025 is 38,967 acre-feet. Over
the life of the Whale Rock Reservoir and dam, the lake
has filled to capacity and spilled 14 times, last spilling in 2024.

The project facilities consist of a 30-inch pipeline, two pumping stations, over two miles of trails and a fishing access area, a maintenance facility and office, and a structure used as the Whale Rock Reservoir Supervisor’s residence. City staff are responsible for ongoing maintenance and operation of this infrastructure, including the inlet and outlet structures, reservoir monitoring instrumentation, access roads, daily reservoir level readings and climatological data, reservoir patrol and security, pipelines and pumping stations, water meters, cathodic protection systems, and other water storage and distribution-related assets. Staff also monitor public access to the lake and perform watershed protection-related work.

Delivery turnouts from the pipeline exist for several private property owners adjacent to the reservoir, the Cayucos Water Treatment Plant, the California Men’s Colony’s water treatment plant, and the City's water treatment plant, which treats water for both the City and Cal Poly. In addition, water can be delivered to the Dairy Creek Golf Course under terms of
an agreement between the California
Men’s Colony and the County of San Luis
Obispo.

The Whale Rock pipeline is
approximately 17 miles long, connecting
the reservoir to the member agencies,
and terminating at the City's Water
Treatment Plant. The design capacity of
the pipeline is 18.94 cubic feet per second
(approximately 8,500 gallons per minute).

The line consists of modified pre-stressed
concrete cylinder pipe at most locations.

Cement mortar lined steel pipe is used at
creek crossings and junctions. The
pipeline has surge protection consisting
of eight-inch, globe type, diaphragmactuated pressure relief valves and surge tanks, which protect the line from excessive pressure surges.

The cathodic protection system consists of sacrificial anodes and test stations located in areas subject to galvanic corrosion. Previous inspections made during routine maintenance and repairs indicate the pipeline is in good condition given its age.

Two pump stations transmit the water through the pipeline to member agencies. The first pump station is located in Cayucos at Chaney Way (elevation 44 feet). The second station is located near Camp San Luis Obispo, approximately six miles southeast of Morro Bay (elevation 181 feet). Each station has five-200 horsepower pumps capable of delivering various flow rates requested by member agencies. Whale Rock generally uses one to three of the five available pumps, providing resiliency in case of infrastructure failure.

Upgrades to both pump stations, which included the addition of two pumps at each station, were completed in August 1993. Whale Rock staff are currently under contract with a design engineer to complete a study WHALE ROCK RESERVOIR, MAY 2026
Whale Rock Reservoir
✓ Potable Water Supply
✓ Low Annual Evaporation
✓ Superior Water Quality
✓ Reliable During Extended Drought

DRAFT
2025 Urban Water Management Plan
35 of the condition of the existing pump stations, which will inform a future project to modernize and upgrade the stations.

Spillway Inspections
In 2018, the City contracted with HDR Engineering, Inc. for inspection and assessment of the 850-foot long Whale Rock Dam spillway. The investigation included:

1. Review of design, construction, inspection, analysis, operation and maintenance, and geologic information, as provided by City.

2. Detailed visual, non-destructive inspection of the spillway slabs and walls from upstream of the spillway crest to downstream of the stilling basin.

3. Video/camera inspection of accessible outfall drains and heel drains.

4. Geologic inspection of foundation material adjacent to the spillway.

5. Evaluation of original spillway design versus a modern spillway design.

6. Evaluation of operations, inspection, and surveillance practices.

7. Evaluation of performance of previous repairs.

A report was completed in March 2019 with recommendations including maintenance and repair activities for the drainage system and further engineering investigations. The City and its Whale Rock partners, Cal Poly and the California Men’s Colony, implemented repairs and a subsequent final
inspection, as recommended by DSOD, and the spillway is functioning as designed.

Operating Agreements
Several agreements establish policies for the operation of the Whale Rock system and actions of the member agencies. A brief description of the existing agreements follows:

1. Agreement for the construction and operation of the
Whale Rock Project, 1957, set forth the project's
capital cost distribution to the member agencies.

2. A supplemental operating agreement, 1960,
established the Whale Rock Commission and
apportioned the operating costs.

3. Downstream water rights agreement (original 1958
agreement was amended and replaced with a new
agreement in April 1996) established water
entitlements for adjacent and downstream water
users. The downstream water users (Cayucos Area
Water Organization or CAWO) affected by this
agreement consist of three public water purveyors
and the cemetery. In addition to the agencies, water entitlements were identified for separate downstream landowners (Error! Reference source not found.).

4. A decision and order by the Fish and Game Commission of the State of California, October 24, 1964, required the Whale Rock Commission to stock the reservoir with 17,500 rainbow trout (between six and eight inches long) each year. The State Department of Fish and Game has directed that no fish be planted in the reservoir to protect the existing fish population in the reservoir (landlocked steelhead).

Downstream Water
Users
Allocation
(AF/Y)
Cayucos Area Water
Organization 600
Paso Robles Beach
Water Association 222
Morro Rock Mutual
Water Company 170
County Water District
#10A 190
Cayucos-Morro Bay
Cemetery District 18
Mainini 50
Ogle 14
Total Downstream
Entitlement: 664
TABLE 6-1: WHALE ROCK RESERVOIR

DOWNSTREAM ENTITLEMENTS

DRAFT
2025 Urban Water Management Plan
36 5. Superior Court decision #36101, 1977, required the Whale Rock Commission to allow public entry to the reservoir for fishing. In 1981, construction was completed on access trails and sanitary facilities at the reservoir, and public fishing began at the lake.

6. An agreement for water allocation and operational policy between the agencies forming the Whale Rock Commission. The agreement established accounting procedures to allow each agency to carry over excess or deficit water each year. The operating policies were most recently amended in 2014 to allow agencies to utilize their water supplies in the reservoir as needed by their agency.

7. An agreement between the Whale Rock Commission and the California Men's Colony, 1990, to establish maintenance and operation criteria for the Chorro Booster pumps. The Chorro Booster pumps were installed by the Commission on the California Men's Colony turnout from the Whale Rock line to reduce system pressures required to provide full flow to the California Men's Colony water treatment plant. Pump station maintenance, according to the agreement, is the responsibility of the California Men's Colony.

8. An agreement between the Whale Rock
Commission and the County of San Luis Obispo
for connection to the Whale Rock pipeline, 1995,
allowed a pipeline connection to deliver water to
the Dairy Creek Golf Course. Typically, the golf
course uses reclaimed water from the California
Men’s Colony Wastewater Treatment Plant.

Water from Whale Rock Reservoir can be
delivered when reclaimed water is not available
under the terms of the agreement.

9. A consent to common use agreement, 1996,
between the Whale Rock Commission and the
County of San Luis Obispo. The agreement
allowed the installation of the State Water
pipeline at seven locations within the existing
Whale Rock pipeline easement.

10. An agreement, updated in 2018, for exchange of
water between the City of San Luis Obispo and
the San Luis Obispo County Service Area No.
10A. The agreement allows for the exchange of
up to 50 acre-feet per year of Nacimiento water
for water from Whale Rock Reservoir.

WHALE ROCK RESERVOIR, MARCH 2024

DRAFT
2025 Urban Water Management Plan
37 6.2.3 Nacimiento Reservoir
In 1959, the San Luis Obispo Flood Control and Watershed Protection District entered into an agreement with Monterey County Flood Control and Water Conservation District (now Monterey County Water Resources Agency) to secure rights to 17,500 acre-feet of water per year from Nacimiento Reservoir.

Nacimiento Reservoir is located entirely within San Luis Obispo County, California (County), and was built by Monterey County Flood Control and Water Conservation District who continues to control reservoir ownership and operations. Nacimiento Reservoir has a storage capacity of 377,900 acre-feet and serves the purpose of abating seawater intrusion in the groundwater aquifers of the Salinas River Valley. The Nacimiento Reservoir also provides flood protection
and is a source of water supply for groundwater
recharge for the Salinas Valley. 1,750 AFY of the
County’s entitlement have been designated for uses
around the lake, leaving 15,750 AFY for allocation to
other areas within the County of San Luis Obispo.

The “dependable yield” from Nacimiento Reservoir is
the contractual amount of water that the City has rights to from Nacimiento Reservoir. The original amount
contracted for was 3,380 acre-feet per year.

Engineering studies, environmental impact reports,
dependable yield analyses, and preliminary design
reports were undertaken in an effort to meet the various water needs within the County. In 2004, the County requested interested agencies to approve the contractual agreements for participation in the Nacimiento Project. The four initial project participants included the cities of San Luis Obispo and Paso Robles, the Atascadero Mutual Water Company, and the Templeton Community Services District. All of these agencies executed participation agreements with San Luis Obispo County for entitlements of water which totaled 9,630 acre feet. On June 29, 2004, the City Council authorized participation in the Nacimiento Water Project for the delivery of the original 3,380 acre-feet of water. In 2004, the County Service Area 10A in Cayucos became a project participant (25 AFY).

The County began construction in 2007 on a 45-mile pipeline project to deliver water from the Nacimiento Reservoir to participating agencies and cities. The facilities consist of a multi-port intake structure, three pump stations, three storage tanks, 45 miles of pipeline, four turnouts, a control center, and a Supervisory Control and Data Acquisition (SCADA) and project control system. The Project budget was $176 million, including design, construction, construction management, environmental permitting, and right-of-way acquisition. Pipeline construction and related water delivery facilities were completed in the fall of 2010 with water deliveries to the City beginning in January of 2011.

In March 2016, the City Council approved the purchase of an additional 2,102 AFY from Nacimiento Reservoir to bolster the City’s water supply portfolio. This addition brought the City’s total allocation to 5,482 AFY. With uncertainty of future climatic conditions, regulation and aging infrastructure, the additional supply of Nacimiento water to the City’s portfolio reduces pressure on use of water supplies in the Whale Rock and Salinas reservoirs. This additional volume would serve to extend these stored supplies in anticipation of and during future critical water shortage periods.

Operations and Distribution
San Luis Obispo County operates, maintains, and administers capital improvement projects for the water delivery system from Nacimiento Reservoir to participating agencies. The Nacimiento Project Commission provides oversight of project operations, maintenance, and the project budget. The Commission is made up of representatives from each of the four founding agencies’ governing boards and a County Representative who is a member of the County Board of Supervisors who also sits on the Board of Directors for the Flood Control District.

Nacimiento Reservoir
✓ Potable Water Supply
✓ 5,482 acre-feet Available Annually
✓ Contractual Supply
✓ Reliable During Extended Drought
✓ Currently Impacted by Broken Pipeline

DRAFT
2025 Urban Water Management Plan
38 6.2.4 Groundwater
The principal source of groundwater for the City is the San Luis Obispo Valley Groundwater Basin (Basin).

The Basin is oriented in a northwest-southeast direction and is composed of unconsolidated or loosely consolidated sedimentary deposits. It is approximately 14 miles long and 1.5 miles wide and covers a surface area of about 12,700 acres, or 19.9 square miles. The Basin is bounded on the northeast by the relatively impermeable bedrock formations of the Santa Lucia Range and on the southwest by the formations of the San Luis Range and the Edna fault system. The bottom of the Basin is defined by the contact of permeable sediments with the impermeable bedrock Miocene-aged and Franciscan Assemblage rocks. The Basin is commonly referenced as being composed of two distinct valleys, with the San Luis Valley in the northwest providing water to the City of
San Luis Obispo and the Edna Valley in the southeast
providing water to unincorporated areas of the county
and large agricultural operations.

Groundwater has historically been an intermittent
source of supply for the City. The City’s major sources of water were groundwater and surface water from
local creeks until 1944, when the City began using
water from Salinas Reservoir. In 1943, the City pumped 1,380 acre-feet of groundwater, and groundwater was used again during the summer of 1948, when 440 acre-feet was pumped. From that point until 1989, most groundwater use within the City was associated with private agricultural use, with limited municipal use for domestic consumption. With the onset of the 1986 drought and declining surface water supplies, the City activated groundwater wells in 1989 to help meet water demand. From 1992 through 2015, the City ceased use of its remaining wells for a variety of reasons, primarily related to reduced overreliance on groundwater and localized contamination issues. Most recently, in April 2015, the City stopped utilizing its last groundwater supply well, the Pacific Beach Well on Los Osos Valley Road, due to more stringent State regulations for hexavalent chromium.

In the 2010 update of the General Plan WWE, the City removed groundwater from the water supply calculation used as a basis for meeting long-term water demands. This approach was continued in the 2015 UWMP and 2020 UWMP because the City was not actively using groundwater as a regular municipal supply and because water quality, infrastructure, and supply reliability considerations limited the City’s ability to rely on groundwater for long-term planning purposes. As a result, previous UWMP planning did not include groundwater as an available long-term supply source.

TABLE 6-2: SURFACE WATER RESERVOIR CHARACTERISTICS
Reservoir Watershed Size
(Square Miles)
Storage Capacity
(Acre-Feet)
Average Annual
Precipitation (Inches)
Average Annual
Evaporation (Inches)
Salinas 112.0 22,508 22.1 85.4
Whale Rock 20.3 38,967 18.7 61.6
Nacimiento 361.5 377,900 35-55 -
Notes:

1. Average annual precipitation and evaporation levels are based on the verified hydrologic data from the City’s safe annual yield mode, 2018. See Appendix IV.

2. Due to the size of the Nacimiento Reservoir watershed area, average precipitation varies significantly throughout the watershed area. Evaporation averages for Nacimiento Reservoir are not currently identified.

Groundwater Supply
✓ Potable Water Supply
✓ Estimated to be Available in FY 2027-28
✓ Safe Annual Yield of 700 Acre-Feet/Year

DRAFT
2025 Urban Water Management Plan
39 Since preparation of the 2020 UWMP, the City has gained substantial additional information regarding the San Luis Obispo Valley Groundwater Basin through implementation of the Sustainable Groundwater Management Act (SGMA), preparation and adoption of the San Luis Obispo Valley Basin Groundwater Sustainability Plan (GSP), and associated hydrogeologic modeling and basin management efforts. These efforts have improved the City’s understanding of groundwater conditions, sustainable yield, basin management requirements, groundwater quality, and the role groundwater can play in the City’s long-term water supply portfolio. Based on this additional information, groundwater is included in the 2025 UWMP as a supplemental local supply source intended to improve supply diversification and resiliency.

The City has also advanced a groundwater cleanup project that is expected to restore the City’s ability to physically extract and treat groundwater for potable use. The City completed a comprehensive characterization of a tetrachloroethylene (PCE) plume that underlies the most productive areas of the groundwater basin and is implementing a groundwater cleanup program that includes installation of eight new monitoring wells, two new extraction wells, and a treatment system utilizing granular activated carbon for PCE removal. This project is supported by State grant funding and is expected to restore groundwater as a supplemental potable water supply beginning in FY 2027-28. Once completed, the project is expected to provide the City with wells and treatment facilities capable of producing and treating groundwater consistent with the volumes identified through the GSP and related planning efforts. The City estimates that the new groundwater wells could
increase available water supplies by
approximately 700 acre-feet per year.

Table 6-3: Groundwater Pumping
Volumes shows the City’s
groundwater production for 2021
through 2025. These production
amounts do not include agricultural or
private groundwater pumping by nonCity entities. As shown in Table 6-3:

Groundwater Pumping Volumes, the
City did not produce groundwater
during the current UWMP reporting
period.

Groundwater Sustainability Plan Adoption and Implementation The San Luis Obispo Valley Groundwater Basin (Basin) is subject to SGMA regulations, which require highand medium-priority groundwater basins to be managed under a Groundwater Sustainability Plan. The City of San Luis Obispo and the County of San Luis Obispo formed Groundwater Sustainability Agencies within their respective jurisdictions to provide groundwater management coverage for the entirety of the Basin.

The San Luis Obispo Valley Basin GSP was recommended for adoption by the Groundwater Sustainability Commission on October 20, 2021, adopted by both the City and County GSAs on December 7, 2021, and submitted to DWR by the January 31, 2022 SGMA deadline. DWR approved the GSP on April 27, 2023.

The GSP provides the framework for long-term sustainable management of the Basin and identifies monitoring, reporting, and implementation actions intended to avoid undesirable results and achieve groundwater sustainability. The City continues to participate in GSP implementation through coordination with the County GSA and other basin stakeholders. Implementation activities include ongoing groundwater level and water quality monitoring, preparation of annual reports, evaluation of basin conditions, and coordination on management actions and projects identified in the GSP.

The City’s planned reinitiation of groundwater production is intended to be consistent with the GSP and the long-term sustainable management of the Basin. Future groundwater use will be coordinated with GSP implementation and will consider basin conditions, water quality, monitoring results, and applicable management criteria established through the SGMA process. Groundwater is included in this UWMP as a supplemental local supply because the City now has improved basin information from SGMA and GSP TABLE 6-3: GROUNDWATER PUMPING VOLUMES
Basin Name 2021 2022 2023 2024 2025
San Luis Obispo
Valley (Basin 3-9) 0 0 0 0 0
Notes:

1. Water volumes are in acre-feet per year.

2. Department of Water Resources, Table 6-1.

DRAFT
2025 Urban Water Management Plan
40 implementation and is advancing treatment and extraction infrastructure needed to restore groundwater production for potable use. Restoration of City groundwater production would provide a supplemental local supply that improves supply diversification and resiliency while remaining subject to GSP implementation and applicable regulatory requirements. It is expected that City staff will propose a modification to the City’s water supply accounting methodology as part of the next WWE update to include groundwater production in future water supply availability calculations.

6.2.5 Recycled Water
The City produces recycled water at the WRRF located on Prado Road in the southern portion of the City.

Recycled water produced at the WRRF is utilized for non-potable beneficial uses and serves to offset potable water demands within the community. The City’s recycled water program is regulated pursuant to Title 22, Division 4 of the California Code of Regulations and the City’s National Pollutant Discharge Elimination System (NPDES) permit requirements administered by the RWQCB.

The City’s recycled water system was constructed as part of the City’s Water Reuse Project, which was completed in 2006. The project included upgrades to the WRRF, construction of approximately eight miles of recycled water distribution pipeline, recycled water storage facilities, and a recycled water pump station.

The recycled water distribution system was designed to
serve a single pressure zone and currently provides
recycled water primarily for landscape irrigation and
construction-related uses.

Recycled Water Coordination
The City owns and operates the wastewater collection
system, WRRF, recycled water treatment facilities,
storage and pumping facilities, and a dedicated
recycled water distribution system serving the City’s
recycled water customers. Because the City is both the wastewater collection/treatment agency and the recycled water supplier within its service area, recycled water planning is coordinated internally among the City’s wastewater treatment, water resources, and engineering sections. The City also coordinates recycled water planning with applicable regulatory and planning agencies, including the Central Coast RWQCB and DDW.

Wastewater Collection, Treatment, and Disposal
The City collects wastewater generated within its service area and conveys it to the WRRF for treatment.

The wastewater collection system serves residential, commercial, industrial, institutional, and governmental customers within and adjacent to the City, including major institutional users such as Cal Poly and the County Regional Airport. Wastewater is conveyed through the City’s collection system to the WRRF for treatment, reuse, or discharge.

The WRRF provides tertiary treatment and disinfection prior to recycled water use or discharge. Following recent facility upgrades completed in 2025, the WRRF has a treatment capacity of approximately 5.4 MGD and is designed to produce high-quality tertiary treated effluent suitable for approved recycled water uses.

Treated effluent that is not used as recycled water is discharged to San Luis Obispo Creek in accordance with the City’s applicable discharge permit requirements. The City is required to maintain minimum treated effluent discharges of approximately 1.6 MGD to San Luis Obispo Creek to support downstream aquatic habitat and fisheries resources. Because this environmental discharge requirement represents an ongoing operational commitment, not all treated effluent is available for recycled water use. The amount of recycled water available for beneficial reuse therefore depends on wastewater influent flows, treatment plant operations, required creek discharge volumes, recycled water storage and pumping capacity, and seasonal customer demand. Table 6-4 documents the volume of wastewater received by the City in FY 2025, as well as the volumes of recycled water sold to customers, discharged to the creek to meet environmental regulations, and the remaining surplus volume after all commitments were met.

Recycled Water Supply
✓ Non-Potable Water Supply
✓ Over 1,000 acre-feet Available Annually
✓ Reliable during 5-Year Drought

DRAFT
2025 Urban Water Management Plan
41 Recycled water availability for planning purposes depends not only on the total volume of treated effluent produced at the WRRF, but also on required San Luis Obispo Creek discharge, customer demand, seasonal irrigation patterns, storage capacity, pumping capacity, and recycled water distribution infrastructure. These factors are evaluated through the City’s Recycled Water Delivery Model, which is discussed further in Section 6.3.5.

Current Recycled Water Use
The City currently delivers recycled water to parks, schools, roadway medians, common landscape areas, Laguna Lake Golf Course, Caltrans landscape irrigation systems, construction water users, and other authorized non-potable uses. Recycled water is distributed through a metered system and is primarily used for landscape irrigation during the dry summer months. The City also maintains a construction water permit program that allows contractors to use recycled water for dust control and soil compaction activities within the community.

Recycled water use varies seasonally. Demands are highest during the summer irrigation season and decline substantially during wetter winter months. As a result, there are periods when treated effluent available after required creek discharge exceeds current beneficial reuse demand.

Projected and Potential Recycled Water Use
Projected recycled water use is based on existing metered recycled water use, anticipated development within the recycled water service area, the City’s mandatory recycled water use ordinance, and planning assumptions from the City’s 2017 Recycled Water Master Plan. Future recycled water use is expected to remain primarily irrigation-driven, with stable use associated with construction water and other authorized non-potable uses where recycled water service is feasible.

The City’s recycled water projections assume continued growth in beneficial recycled water use over time as additional customers connect to the recycled water system or increase use where service is available.

For planning purposes, the City assumes recycled water demand will increase by approximately 10 acrefeet per year over the UWMP planning horizon. These projected uses are reflected in the normal-year nonpotable supply volumes presented in Section 6.4.3.

TABLE 6-4: TREATED WASTEWATER USES WITHIN CITY IN FY 2025 (IN ACRE-FEET) Total Wastewater
Treated Required Creek Releases Recycled Water Demand Surplus Recycled Water 4,488 1,792 288 2,408
TABLE 6-5: FY 2025 RECYCLED WATER DEMAND BY CUSTOMER CLASS Customer Class FY 2025 FY 2030 FY 2035 FY 2040 FY 2045 FY 2050 Landscape
Irrigation (excluding
golf course)
243 293 343 393 443 493
Golf Course
Irrigation 33 33 33 33 33 33
Construction Water 12 12 12 12 12 12

DRAFT
2025 Urban Water Management Plan
42 In addition to forecasting and planning for the expanded use of non-potable recycled, the City has also identified potential future recycled water opportunities that could increase beneficial reuse beyond currently projected demands. These opportunities may include service to additional development areas, retrofit of existing potable irrigation accounts, increased construction water use, expanded non-potable distribution infrastructure, indirect potable reuse, direct potable reuse, or other beneficial reuse applications. These potential uses would require additional technical analysis, infrastructure planning, regulatory review, environmental evaluation, cost analysis, public engagement, and future City Council direction before being implemented or relied upon as future water supplies.

Actions to Encourage and Optimize Future Recycled Water Use The City will continue to evaluate opportunities to optimize and expand recycled water use where feasible.

The City has adopted a mandatory recycled water use ordinance codified in Municipal Code Chapter 13.24, which authorizes the City to require recycled water use in lieu of potable water where recycled water service is determined to be feasible. This ordinance supports continued expansion of irrigation-driven recycled water use as development occurs within or near the recycled water service area.

The City’s 2017 Recycled Water Master Plan identified future recycled water expansion opportunities, including service to planned development areas, retrofit of existing irrigation systems, hydraulic improvements, storage considerations, and potential future beneficial reuse applications. The City will continue to evaluate these opportunities based on infrastructure feasibility, seasonal demand, available treated effluent after required creek discharge, customer readiness, cost, regulatory requirements, and consistency with City planning objectives.

6.3 Water Supply Modeling and Yield Assessment

6.3.1 Overview of Water Supply Planning Methodology
Long-Term Water Supply Planning
The City uses related but different methods to evaluate long-term water supply reliability and near-term operational reliability within the 2025 UWMP. These methods serve different purposes and rely on different types of information.

For long-term water supply planning, the City relies on the policy framework established in the General Plan and WWE. The WWE includes both a water resource availability calculation and a water supply accounting framework. The water resource availability calculation identifies the City’s recognized water supply sources and long-term planning adjustments. The WWE identifies the available yield from each water resource based on the nature of that source, including safe annual yield for Salinas and Whale Rock Reservoirs, contractual supply from Nacimiento Reservoir, prior-year recycled water use, and a long-term deduction for expected reservoir siltation.

The WWE water supply accounting framework then evaluates the City’s available water resources in relation to three community needs: primary water supply, reliability reserve, and secondary water supply.

Primary water supply represents the amount of water needed to serve the General Plan buildout population.

Reliability reserve provides a buffer for future unforeseen or unpredictable long-term impacts to the City’s available water resources. Secondary water supply represents remaining water resources after accounting for primary water supply and reliability reserve and is intended to help address peak demand periods or short-term loss of City water supply sources.

For purposes of the 2025 UWMP, the City applies the WWE framework using the best available current supply information and the planning horizon required for the UWMP. Long-term water resource availability includes the City’s contractual supply from Nacimiento Reservoir, the combined safe annual yield of Salinas

DRAFT
2025 Urban Water Management Plan
43 and Whale Rock Reservoirs, recycled water use as a non-potable supply, and a reduction in available supply to account for future siltation in Salinas and Whale Rock reservoirs. The 2025 UWMP also evaluates planned groundwater production as a future supplemental potable supply when available. Because groundwater was not included as an available supply in prior UWMP accounting, this UWMP identifies groundwater as a potential source of supply and explains the basis for including it in future reliability analysis.

For UWMP presentation and reliability analysis, potable and non-potable supplies are shown separately where appropriate. Salinas Reservoir, Whale Rock Reservoir, Nacimiento Reservoir, and planned groundwater production are evaluated as potable supplies. Recycled water is evaluated as a non-potable supply that offsets potable demand where recycled water service is available, feasible, and authorized. This presentation helps distinguish between supplies available to meet potable demands and recycled water supplies available for approved non-potable uses, while remaining consistent with the WWE’s broader water resource availability and supply accounting framework.

Near-Term Water Supply Planning
The City conducts near-term operational reliability analysis for upcoming single-year assessments, the fiveyear drought risk assessment, and WSCP implementation using a different methodology because these analyses serve a different purpose than long-term water supply planning. Rather than evaluating long-term supply sufficiency for General Plan consistency, near-term analyses evaluate whether the City can meet expected demands during a specific upcoming period and whether shortage response actions may be needed.

For near-term operational reliability analysis, the City uses its Water Projection Model informed by current or projected near-term conditions. Model inputs may include actual reservoir storage, groundwater availability, recycled water availability, recent community water use, current population estimates, seasonal demand patterns, known or anticipated infrastructure constraints, and dry-year hydrologic assumptions.

This approach is more appropriate for near-term evaluations because the City has better information about actual operating conditions and expected customer demand over a one- to five-year period than would be reflected by applying long-term buildout demand assumptions and long-term supply planning values that were developed in order to plan for future community growth.

The City’s Water Projection Model is separate from, but complementary to, the City’s long-term supply planning tools. The safe annual yield model for Salinas and Whale Rock Reservoirs estimates the longterm reliable annual supply from the coordinated operation of the two reservoirs under historical and modeled hydrologic conditions. The Water Projection Model is used as an operational and planning tool to evaluate how current storage, projected demands, Nacimiento deliveries, groundwater availability, recycled water use, infrastructure constraints, and hydrologic assumptions may affect the City’s ability to meet demands over a defined near-term period.

Using different methods for long-term planning and near-term operational analysis helps ensure that each analysis is appropriately matched to its purpose. Applying current demands alone to long-term planning could understate future needs and would not provide the conservative basis needed for General Plan consistency and multi-decade water supply planning. Conversely, applying long-term buildout population assumptions and the 117 gpcd planning value to near-term operational analyses could overstate expected customer demand and misrepresent actual shortage risk during upcoming assessment periods.

6.3.2 Salinas and Whale Rock Safe Annual Yield Modeling and Reliability The City utilizes a computer-based hydrologic and operational model to evaluate the coordinated operation of Salinas Reservoir and Whale Rock Reservoir and to estimate the combined safe annual yield of the two reservoirs. Safe annual yield represents the quantity of water that can be reliably withdrawn jointly from the two reservoirs on a long-term basis while maintaining acceptable levels of reliability under varying hydrologic conditions.

DRAFT
2025 Urban Water Management Plan
44 Salinas Reservoir and Whale Rock Reservoir are operated conjunctively because the two reservoirs have different physical, hydrologic, and climatic characteristics. Salinas Reservoir has a larger watershed and smaller storage
capacity than Whale Rock Reservoir, allowing it to respond more quickly to runoff events and recover storage more
readily under favorable hydrologic conditions. However, Salinas Reservoir is located farther inland, where warmer temperatures and higher evaporation rates can cause stored water to decline more quickly than at Whale Rock Reservoir.

On the converse, Whale Rock Reservoir has a smaller
watershed but approximately double the storage capacity.

Because of this, Whale Rock Reservoir generally requires more sustained rainfall and runoff to refill, but once water is stored, the reservoir experiences lower evaporation rates due to its cooler coastal location.

These differences make the two reservoirs complementary. Salinas Reservoir provides operational flexibility and the ability to recover storage more quickly during favorable hydrologic conditions, while Whale Rock Reservoir provides larger carryover storage and lower evaporative losses to help sustain supplies during extended dry periods.

The City’s joint operation of Salinas and Whale Rock Reservoirs is intended to maximize the reliability of the combined reservoir system. Operational decisions consider reservoir storage levels, runoff conditions, evaporation, seasonal demands, downstream release requirements, water quality, treatment and conveyance limitations, and the long-term need to preserve supply reliability. In general, the City may prioritize use of Salinas Reservoir when water is available, while Whale Rock Reservoir provides supplemental supply and longer-term carryover storage benefits as part of the combined reservoir system.

The coordinated operation of Salinas and Whale Rock Reservoirs is evaluated through the City’s Safe Annual Yield (SAY) model. The model simulates the combined operation of the two reservoirs under historical hydrologic conditions and estimates the quantity of water that can be reliably withdrawn while maintaining acceptable levels of reliability. Because the model reflects the conjunctive operation of the two reservoirs, the resulting safe annual yield represents the combined reliable yield of the Salinas and Whale Rock reservoir system rather than the independent yield of either reservoir.

The City’s SAY model was first developed in 1988. At that time, the 1946–1951 drought was the controlling drought period. The model was updated in 1991 to incorporate the 1986–1991 drought, which became the new controlling condition for estimating safe annual yield. Based on that update, the City estimated the combined SAY from Salinas and Whale Rock Reservoirs to be 6,940 acre-feet per year. This value was used in prior City planning documents, including UWMPs prior to the 2020 UWMP and updates to the General Plan WWE. Following the extended 2006–2016 drought period, the City initiated an update to the SAY model. The update was intended to verify historical hydrologic input data, document and validate model calculations, incorporate the full extent of the 2006–2016 drought period, and evaluate potential climate change effects. The updated model incorporated verified historical data for reservoir inflows, precipitation, evaporation, and downstream releases. The updated analysis resulted in a revised combined SAY estimate of 4,910 acre-feet per year for Salinas and Whale Rock Reservoirs. This represented a reduction of approximately 2,000 acre-feet per year from the previously used estimate of 6,940 acre-feet per year. Two primary factors contributed to this reduction. First, updated historical evaporation data showed evaporation losses approximately 30 percent higher than the prior model. Second, the updated model incorporated the full 2006–2016 drought period, which was more severe than the 1986–1991 drought and became the new controlling drought period for estimating SAY.

To provide flexibility, the updated model evaluated potential climate change scenarios using projections from EPA’s Climate Resilience Evaluation and Awareness Tool, SLOCOG’s 2014 Regional Transportation Plan, the Nature Communications Journal, and other published climate information. These scenarios produced a range of potential future SAY values. EPA climate change scenarios resulted in modeled safe annual yield values ranging from approximately 4,690 to 5,050 acre-feet per year, SLOCOG scenarios Conjunctive use refers to the
coordinated operation of multiple water
supplies to improve overall system
reliability. The City operates Salinas and
Whale Rock reservoirs together by
balancing reservoir use based on
available storage, hydrologic conditions,
operational constraints, treatment needs,
and long-term supply reliability.

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45 ranged from approximately 4,050 to 5,070 acre-feet per year, and the Nature Communications Journal7 climate change scenario resulted in a modeled value of approximately 4,950 acre-feet per year.

Because of uncertainty regarding future precipitation, runoff, and evaporation patterns on the Central Coast, the City uses the updated 4,910 acre-foot per year safe annual yield estimate as a conservative planning value for Salinas and Whale Rock Reservoirs. The SAY model is intended to remain a planning and operational tool that can be updated as additional hydrologic data become available. Continued coordination between the City, Cal Poly, and other Whale Rock Reservoir stakeholders is important to maintaining an accurate understanding of expected reservoir supply availability.

Updated Bathymetric Information and Safe Annual Yield Planning Assumptions In 2024, the City received updated bathymetric information for Salinas Reservoir. The updated information estimated the long-term reservoir storage loss due to siltation at approximately 46.27 acre-feet per year.

This value is generally consistent with the siltation assumptions used in prior water supply planning and safe annual yield modeling efforts.

The City’s current combined SAY estimate for Salinas and Whale Rock Reservoirs is 4,910 acre-feet per year, as described above. This value was developed through the City’s updated SAY model, which incorporated verified historical hydrologic data, updated evaporation information, reservoir operations, downstream release requirements, and the extended 2006–2016 drought period. The 4,910 acre-foot per year value remains the City’s current planning basis for the combined Salinas and Whale Rock Reservoir supplies.

The updated 2024 bathymetric information does not result in an immediate change to the safe annual yield value used in this UWMP. The City’s long-term water supply planning already includes a conservative 500 acre-foot per year reduction to account for future reservoir siltation. The updated Salinas Reservoir siltation estimate of 46.27 acre-feet per year remains within the planning buffer provided by this reduction and does not indicate a material change requiring immediate recalculation of the safe annual yield model.

The City will incorporate the 2024 Salinas Reservoir bathymetric information into the next comprehensive updates of the WWE and SAY model. Future updates to the model may also incorporate additional hydrologic data, updated evaporation information, reservoir storage information, climate-related assumptions, operational considerations, and any updated bathymetric information for Whale Rock Reservoir. This approach allows the City to maintain conservative and reliable water supply planning assumptions while avoiding piecemeal annual revisions to the SAY estimate based on individual data updates.

6.3.3 Nacimiento Water Supply Reliability
In 2002, the San Luis Obispo County Flood Control and Water Conservation District (District) retained the services of Boyle Engineering Corporation to assess the ability of the Nacimiento Reservoir to reliably provide the District’s entitlement of 17,500 AFY to the District contractors. As part of the analysis, the study took into account the agreement with the Monterey County Water Resources Agency (MCWRA), which owns and operates the Nacimiento Reservoir facilities, that stipulates that the District entitlement through operational procedures will be “preserved” in the reservoir due to MCWRA being contractually obligated to maintain a “minimum pool” for the benefit of the District. This enables the District to maintain deliveries to the participating agencies even when reservoir levels are low, meaning that unless the water storage capacity drops below the “dead pool” of the reservoir, the District’s entitlement will always be available. The 2002 study took into account the following factors:
• Short-term power outages
• Delivery facility failure
7 Technical Memorandum, Salinas and Whale Rock Reservoirs Safe Annual Yield (Water Systems Consulting, January 2018)

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46 • Energy costs
• Drought
• Contamination of supply
• Environmental restrictions
Upon completion of the analysis, the 2002 study summarized that even though there have been several periods of drought, both short-term and long-term, the total annual entitlement for the District could be delivered consistently, even in periods of extended drought.

During the worst-case drought on record in the region (2012 to 2015), Nacimiento Reservoir remained a resilient water supply capable of providing a consistent and reliable source of water for San Luis Obispo County, which includes the City’s contractual amount of 5,482 acre-feet per year. To confirm the prior analysis with more recent data, the City reviewed rainfall and inflow data from 2013 which was the driest year on record. Over that year, Nacimiento Reservoir received 35,000 acre-feet of inflow. Though this is significantly below the average inflow into the reservoir, the District’s entitlement could still be met if inflow remained at this level.

Based on the 2002 reliability analysis, the contractual minimum pool requirements, and more recent drought-period inflow data, Nacimiento Reservoir is considered a reliable component of the City’s potable water supply portfolio for purposes of the 2025 UWMP and associated drought planning.

In the short-term, recent damage to the Nacimiento
pipeline has resulted in reductions to available supplies that should be considered when planning near-term
deliveries. In January 2023, atmospheric river storm
events caused significant flooding within the Salinas
River and damaged portions of the Nacimiento raw
water transmission pipeline. Following the storm
damage, deliveries of Nacimiento water to the City
were interrupted. A temporary pipeline was
subsequently installed in July 2025 to restore partial
deliveries of Nacimiento water to the City. The
temporary pipeline is capable of delivering
approximately 3.2 MGD to the City’s WTP; however,
operation of the temporary facility is prohibited during periods when streamflow is present within the Salinas
River. The City continues to coordinate with
participating agencies regarding long-term repair and
restoration of the Nacimiento transmission system and
the pipeline, which is expected to be restored to full
capacity in FY 2027-28.

6.3.4 Groundwater Supply Reliability / Planned
Groundwater Supply
Groundwater is not currently relied upon to meet the
City’s existing potable water demands; however, the
City is implementing projects intended to restore
groundwater production as a supplemental potable
water supply. As described in Section 6.2.4, groundwater was not included as a long-term available supply in prior planning documents because it was not an active potable source and had water quality and reliability limitations. For the 2025 UWMP, planned groundwater production is included as a future supplemental supply because the City has improved its understanding of the capacity and functionality of the groundwater basin through development of the GSP. Accordingly, the City is currently constructing new groundwater monitoring, extraction, and treatment infrastructure needed to restore potable groundwater use.

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2025 Urban Water Management Plan
47 The planned groundwater supply is expected to improve operational flexibility, diversify the City’s water supply portfolio, and provide additional resiliency under drought or infrastructure-constrained conditions.

With this, groundwater would be operated as part of the City’s integrated water supply portfolio rather than as an independent supply source. The City’s primary potable supplies would remain its three surface water reservoirs, with groundwater production used to supplement these supplies, support reservoir storage management, reduce reliance on surface water during certain conditions, and provide redundancy during drought or infrastructure-related constraints.

Future City groundwater production will be coordinated with implementation of the San Luis Obispo Valley GSP and will consider groundwater levels, water quality, basin management criteria, treatment capacity, water level and water quality monitoring results, and other applicable regulatory requirements. The timing and quantity of groundwater production would also be coordinated with Salinas and Whale Rock Reservoir storage conditions, Nacimiento delivery availability, overall system demands, and the City’s long-term supply reliability objectives.

For purposes of this UWMP, groundwater is assumed to become available beginning in FY 2027–28 and is projected to provide up to 700 acre-feet per year under normal planning conditions. This supply is incorporated into the City’s projected water supply portfolio beginning with the 2030 planning increment, the first five-year UWMP planning increment following anticipated implementation.

Consistent with the sustainable management criteria outlined in the Groundwater Sustainability Plan, the City may apply source-specific dry-year adjustments to assumed groundwater availability to avoid or minimize potential impacts to surface water flows and basin conditions. As a result, groundwater availability may be lower during dry-year or multiple dry-year planning scenarios than under normal planning conditions. These assumptions are reflected in the water service reliability analyses presented in Chapter

7. As the City completes groundwater treatment and extraction facilities and begins operating the restored groundwater supply, staff anticipate recommending that future updates to the General Plan WWE and water supply accounting methodology be revised to include groundwater production in future water supply availability calculations, as appropriate.

6.3.5 Recycled Water Supply Reliability
Recycled water is an important non-potable supply that offsets potable water demand where recycled water service is available. The City produces recycled water at the Water Resource Recovery Facility (WRRF), where treated effluent is available for approved non-potable uses after accounting for required discharge to San Luis Obispo Creek and applicable regulatory requirements. Recycled water is evaluated separately from potable water because it is not available to meet drinking water demands and is limited by customer demand, seasonal irrigation patterns, storage capacity, pumping capacity, distribution infrastructure, WRRF operations, and regulatory discharge obligations.

The City uses a Recycled Water Delivery Model to evaluate non-potable recycled water availability under current and projected system conditions. The model considers expected wastewater influent flows, recycled water production, storage tank capacity, pump station capacity, customer demand volumes, seasonal demand patterns, and required discharge to San Luis Obispo Creek. The model is used to estimate the amount of recycled water that can reasonably be made available for approved non-potable uses, rather than simply reporting the total theoretical volume of treated effluent produced at the WRRF. This distinction is important because recycled water reliability depends not only on the amount of treated effluent produced, but also on the City’s ability to store, pump, distribute, and beneficially use recycled water when demand occurs.

Based on recent modeling, recycled water availability is not limited by the total volume of treated wastewater effluent available for reuse. Instead, the primary near-term limiting factor is the City’s current recycled water

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2025 Urban Water Management Plan
48 pumping capacity at the WRRF. Accordingly, the City distinguishes between total recycled water produced and the amount of recycled water that can reasonably be stored, pumped, and delivered with existing infrastructure. This distinction is important when evaluating recycled water availability for near-term assessments and future planning.

For long-term UWMP planning, recycled water supply reliability is evaluated based on current recycled water use, anticipated growth in recycled water demand, potential future customer connections, system capacity, regulatory discharge requirements, and opportunities to expand beneficial reuse over time. The City’s recycled water planning assumptions reflect continued growth in recycled water use, including an estimated increase in customer demand of approximately 10 acre-feet per year as additional customers connect to the recycled water system and existing uses expand where feasible.

The City currently produces recycled water in excess of existing customer demand, including during dry periods when irrigation demand is higher. This provides a reliable non-potable resource for existing recycled water customers and supports future opportunities to offset potable demand. However, the amount of recycled water that can be used beneficially is constrained by the timing and location of demand, delivery infrastructure, pump station capacity, storage capacity, and required San Luis Obispo Creek discharge.

Future increases in recycled water use will depend on the City’s ability to match available recycled water supply with customers that can use recycled water when and where it is available. This may require additional customer connections, distribution system improvements, pumping or storage capacity, operational changes, or regulatory coordination.

The City will continue to evaluate recycled water system expansion, optimization of existing recycled water deliveries, and future opportunities for increased beneficial use. These efforts may include additional nonpotable reuse, expanded customer connections, delivery system improvements, and continued evaluation of potable reuse opportunities. Potable reuse is being studied and considered as a potential future water supply strategy, but it is not relied upon as an existing or projected potable supply in this UWMP.

6.4 Current Year Water Use and Normal-Year Supply Availability

6.4.1 Current Year Water Supply and Demand
The City reports actual water supply volumes on a fiscal-year basis for purposes of this UWMP. In this plan, the current year is reported as FY 2025, which represents the period from July 1, 2024, through June 30, 2025. Accordingly, references to current-year actual water supply use in this section mean actual water supply volumes used during FY 2024–25.

Actual water supply volumes used during FY 2025 differ from the City’s normal-year supply availability because Nacimiento Reservoir deliveries were unavailable due to damage to the Nacimiento transmission pipeline caused by 2023 storms. As a result, the City’s current-year water use by source does not reflect the City’s expected normal-year supply portfolio when the Nacimiento transmission system is available.

The absence of Nacimiento deliveries in FY 2025 reflects a temporary conveyance limitation rather than a permanent change in the City’s Nacimiento Reservoir entitlement or long-term supply planning assumptions. Table 6-6 summarizes actual FY 2025 source use and does not represent the City’s normalyear supply availability. Projected normal-year potable and non-potable supply volumes are presented in Sections 6.4.2 and 6.4.3.

TABLE 6-6: FY 2025 ACTUAL WATER SUPPLY USE BY SOURCE
Water Supply Source Potable or Non-Potable FY 2025 Volume Used (acre-feet) Salinas Reservoir Potable 2,385
Whale Rock Reservoir Potable 2,448
Nacimiento Reservoir Potable 0
Non-Potable Recycled Water Non-Potable 288

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49 Subtotal for Potable 4,833
Subtotal for Non-Potable 288
Total Use (Potable and Non-Potable) 5,121
Notes:

1. Nacimiento Reservoir was not utilized in FY 2025, as it was offline due to pipeline damage from 2023 storms.

2. Groundwater was not utilized as a water supply in FY 2025.

3. Values are rounded to nearest whole number.

6.4.2 Projected Normal-Year Potable Water Supply Volumes Under normal operating conditions, the City’s potable water supply portfolio includes surface water from Salinas Reservoir, Whale Rock Reservoir, and Nacimiento Reservoir, with planned groundwater production expected to become available beginning in FY 2027-28. Projected normal-year potable water supply volumes are shown in Table 6-7 and represent the City’s estimated potable supply availability over the UWMP planning horizon based on existing water rights, ownership interests, contractual entitlements, infrastructure capacity, treatment capacity, planned projects, and adopted water supply planning assumptions.

Salinas and Whale Rock Reservoirs are shown as a combined potable supply because the City evaluates these reservoirs through a combined safe annual yield analysis. As described in Section 6.3.2, the City’s safe annual yield model evaluates the coordinated operation of the two reservoirs using historical hydrology, reservoir inflows, precipitation, evaporation, downstream releases, withdrawals, and minimum pool constraints. The updated model, which incorporated the extended 2006–2016 drought period, resulted in a revised combined safe annual yield of 4,910 acre-feet per year. For long-term planning purposes, the City applies a 500 acre-foot per year adjustment to account for future reservoir siltation. Accordingly, the projected normal-year potable supply volume shown in Table 6-7 for Salinas and Whale Rock Reservoirs is 4,410 acre-feet per year.

Nacimiento Reservoir is shown at 5,482 acre-feet per year, reflecting the City’s contractual entitlement. The projected normal-year volumes assume restoration of Nacimiento conveyance capacity following completion of permanent pipeline repairs, currently estimated to occur in FY 2027-28.

Groundwater is shown as a planned future potable supply beginning with the 2030 planning increment.

Although groundwater was not used during FY 2025 and was not included as an available supply in the 2020 UWMP, the City is implementing projects intended to restore groundwater production as a supplemental potable supply beginning in FY 2027–28. For UWMP planning purposes, groundwater is incorporated into projected normal-year supply availability beginning in 2030, the first five-year planning increment after expected implementation.

TABLE 6-7: PROJECTED NORMAL-YEAR POTABLE WATER SUPPLY VOLUMES (IN ACRE-FEET) Water Supply Source 2030 2035 2040 2045 2050
Salinas and Whale Rock Reservoirs 4,410 4,410 4,410 4,410 4,410 Nacimiento Reservoir 5,482 5,482 5,482 5,482 5,482
Groundwater 700 700 700 700 700
Total Potable Water Supply Availability 10,592 10,592 10,592 10,592 10,592 Notes:

1. Salinas and Whale Rock Reservoirs are shown combined because the City evaluates these reservoirs through a combined safe annual yield analysis.

2. Nacimiento Reservoir projections assume restoration of conveyance capacity following completion of permanent pipeline repairs, which are currently estimated to occur in 2027.

3. Groundwater production is planned to begin during FY 2027-28

4. Groundwater was not utilized as a water supply in FY 2025 or in the 2020 UWMP.

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50 6.4.3 Projected Normal-Year Non-Potable Water Supply Volumes The City’s non-potable water supply consists of recycled water produced at the WRRF and delivered for approved non-potable uses. Recycled water is evaluated separately from potable water because it is not available to meet drinking water demands and is served through separate recycled water infrastructure.

Recycled water use offsets potable water demand where recycled water service is available, but the amount of recycled water that can be beneficially used depends on customer demand, seasonal irrigation patterns, distribution system capacity, pumping capacity, storage capacity, WRRF operations, and regulatory discharge requirements.

For UWMP planning purposes, projected normal-year non-potable supply volumes represent the amount of recycled water expected to be available for approved beneficial use during the planning horizon. These projections consider existing recycled water use, anticipated growth in recycled water demand, potential future customer connections, system capacity, and the City’s ongoing efforts to optimize recycled water use within City limits.

The City uses a Recycled Water Delivery Model to evaluate recycled water availability under current and projected system conditions. The model considers wastewater influent flows, recycled water production, storage tank capacity, pump station capacity, customer demand volumes, seasonal demand patterns, and required discharge to San Luis Obispo Creek. The model helps distinguish between the total volume of treated effluent produced at the WRRF and the amount of recycled water that can reasonably be stored, pumped, delivered, and used due to known infrastructure limitations.

Recent recycled water modeling indicates that recycled water availability is not limited by the total volume of treated effluent produced at the WRRF. Instead, the primary near-term limiting factor is the City’s current recycled water pumping capacity at the WRRF. For this reason, near-term recycled water availability estimates are based on the amount of recycled water that can reasonably be stored, pumped, and delivered with existing infrastructure, rather than the larger volume of treated effluent that may be produced at the WRRF.

For long-term UWMP planning, the City assumes continued growth in recycled water use over time. The City’s recycled water planning assumptions include an estimated increase in customer demand of approximately 10 acre-feet per year as additional customers connect to the recycled water system and existing uses expand where feasible. Future increases in recycled water use will depend on the City’s ability to match available recycled water supply with customers that can use recycled water when and where it is available. This may require additional customer connections, distribution system improvements, pumping or storage capacity, operational changes, or regulatory coordination. Table 6-8 summarizes the City’s projected normal-year non-potable recycled water supply volumes through the UWMP planning horizon.

TABLE 6-8: PROJECTED NORMAL-YEAR NON-POTABLE WATER SUPPLY VOLUMES (IN ACRE-FEET) Non-Potable Water Supply Source 2030 2035 2040 2045 2050 Recycled Water from City WRRF 1,296 1,296 1,296 1,296 1,296

6.4.4 Energy Use Information
California Water Code section 10631.2 requires urban water suppliers to include energy-related information that can be readily obtained. The City’s water system uses energy to convey, treat, store, and distribute potable and non-potable water. Energy use generally varies from year to year based on water demand, source selection, reservoir levels, treatment requirements, demand patterns, actual water use, and other operational conditions.

The City relies on multiple water supply sources, including Salinas Reservoir, Whale Rock Reservoir,

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2025 Urban Water Management Plan
51 Nacimiento Reservoir, and recycled water. Estimating source-specific raw water conveyance energy can be difficult because several of the City’s water sources involve shared facilities, regional conveyance systems, or jointly managed infrastructure that also serve or benefit other water purveyors. As a result, raw water conveyance energy is not readily obtainable and is therefore not provided.

For this UWMP, the City provides readily available energy information associated with City-operated potable water treatment and distribution facilities. The City’s Water Treatment Plant uses energy for treatment processes, chemical feed systems, ozone generation, pumping, plant service water, monitoring and control systems, and other facility operations. After treatment, additional energy is required to move water through portions of the City’s distribution system, including pump stations, pressure zones, storage facilities, and related control systems.

Energy use is closely related to water demand and system operations. Higher water demands generally increase the amount of water that must be treated, pumped, stored, and delivered. However, annual energy use may also vary depending on the mix of supplies used, the elevation and location of demands served, reservoir operating conditions, water quality, recycled water production, groundwater availability, and infrastructure constraints.

The City considers energy use as one factor in water system operations, infrastructure planning, capital project development, and long-term resiliency planning. However, energy use is not evaluated independently from water supply reliability, public health, treatment requirements, regulatory compliance, infrastructure condition, emergency preparedness, cost, and operational flexibility. Detailed source-specific energy intensity calculations are voluntary under DWR’s methodology and are not currently used as a primary water supply planning metric by the City. The City will continue to evaluate readily available energy information through water system operations, capital planning, and future UWMP updates. Table 6-9: FY 2025 Potable Water-Related Electricity Use documents readily available City-operated potable water treatment and distribution electricity use during FY 2025.

TABLE 6-9: FY 2025 POTABLE WATER-RELATED ELECTRICITY USE Water Treatment/Delivery
Function
Energy Demand
(kWh)
Water Produced/Delivered
(acre-feet) kWh/acre-foot
Water Treatment 1,804,616 4,832 373.47
Water Distribution 103,670 4,832 21.45
Total 1,908,286 4,832 394.93
Notes: Source water pumping data was not readily available at the time this report was prepared and is not included in this table.

6.5 Planned Water Supply Projects and Programs
The City continues to implement and evaluate projects and programs intended to maintain and improve water supply reliability, operational flexibility, and long-term resiliency. These efforts include restoration of full Nacimiento Reservoir conveyance capacity, restoration of groundwater production, continued recycled water system expansion, consideration of potable reuse, and studies related to regional desalination feasibility.

Nacimiento Transmission System Restoration
The City is coordinating with Nacimiento Project participating agencies regarding long-term repair and restoration of the Nacimiento transmission pipeline. Full restoration of the Nacimiento pipeline is expected in FY 2027-28. Once full conveyance capacity is restored, the City expects Nacimiento Reservoir to continue serving as a reliable component of the City’s potable water supply portfolio.

Planned Groundwater Production
As noted above, the City is implementing projects intended to restore groundwater as a supplemental potable water supply. These efforts include groundwater cleanup, installation of new monitoring and

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52 extraction wells, treatment facilities, and related operational and regulatory coordination. Groundwater is projected to become available in FY 2027-28 and is therefore included with the 2030 planning increment.

The projected groundwater supply volume is anticipated to be 700 acre-feet per year in normal-year conditions, with reduced volumes available during dry-year conditions.

Recycled Water System Expansion
The City will continue to evaluate opportunities to optimize and expand recycled water use where feasible.

The City’s 2017 Recycled Water Master Plan identified future recycled water expansion opportunities and included demand forecasts that assume continued growth in customer use of recycled water over time. For planning purposes, those forecasts assume that recycled water demand will increase by approximately 10 acre-feet per year as additional customers connect to the recycled water system.

Potable Reuse
The City continues to evaluate potable reuse as a potential long-term water supply resiliency strategy.

Potable reuse could include indirect potable reuse, such as groundwater recharge or surface water augmentation, or direct potable reuse, subject to applicable State regulations, technical feasibility, public health requirements, environmental review, infrastructure needs, cost, public engagement, and future City Council direction. Potable reuse is being studied as a potential future supply opportunity and is not included in the projected water supply volumes or reliability calculations presented in this UWMP.

Desalination
The City is monitoring and participating in regional discussions related to seawater desalination feasibility.

The San Luis Obispo County Flood Control and Water Conservation District is leading a regional desalination feasibility planning effort to evaluate potential project alternatives, costs, constraints, and implementation considerations. While desalination could potentially provide a drought-resilient regional water supply in the future, it remains under study and is not included in the City’s projected water supply availability or reliability calculations in this UWMP.

6.6 Climate Change and Water Supply Considerations
Climate variability and climate-related uncertainty are important considerations in long-term water supply planning. Potential climate-related effects relevant to the City’s water supply portfolio include changes in precipitation patterns, increased frequency or severity of drought, changes in watershed runoff timing and volume, increased evaporation, increased wildfire risk, degradation of raw water quality, and increased stress on water infrastructure during extreme weather events.

Because the City relies primarily on surface water supplies from multiple watersheds, changes in rainfall, runoff, reservoir inflows, evaporation, and watershed conditions may affect long-term supply availability.

The City’s revised safe annual yield analysis for Salinas and Whale Rock Reservoirs incorporates updated historical hydrologic information, including the extended 2006–2016 drought period, and provides a conservative basis for long-term supply planning. In addition, the City evaluated climate-related uncertainty through separate climate sensitivity scenarios as part of the safe annual yield model update, allowing for model runs to be conducted for a variety of climate scenarios.

The City’s safe annual yield model update evaluated potential climate change effects on Salinas and Whale Rock Reservoirs using multiple climate projection sources, including EPA’s Climate Resilience Evaluation and Awareness Tool, SLOCOG climate projections, and other published climate information. The climate scenarios evaluated changes in precipitation, reservoir inflow, and evaporation. The resulting modeled safe annual yield values ranged from approximately 4,050 acre-feet per year to 5,070 acre-feet per year, depending on the climate scenario. These results demonstrate that future reservoir yield is sensitive to changes in precipitation, runoff, and evaporation. They also support the City’s continued use of conservative planning assumptions, including the updated 4,910 acre-foot per year safe annual yield value, a separate 500 acre-foot planning adjustment for future reservoir siltation, and continued efforts to diversify the City’s water supply portfolio.

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53 Climate-related uncertainty may also affect water quality, treatment operations, and infrastructure reliability.

Intense storm events can increase turbidity, organic matter, debris, and other water quality challenges in surface water supplies. Extended dry periods may reduce reservoir inflows and degrade water quality within each reservoir, most notably Salinas Reservoir due to its smaller storage volume and warmer inland climate. Wildfire, watershed disturbance, and post-fire runoff may also affect reservoir water quality and cause unanticipated reservoir capacity loss due to sedimentation.

These considerations reinforce the importance of maintaining a diversified supply portfolio, investing in resilient water infrastructure, periodically updating hydrologic and operational models, and continuing planning and feasibility efforts aimed at expanding and diversifying the City’s water supply portfolio with more drought-resilient supplies, such as potable reuse and/or participation in a regional desalination project, subject to the discretion of the San Luis Obispo City Council.

6.7 Transfers and Exchanges
California Water Code section 10631(c) requires urban water suppliers to describe opportunities for exchanges or transfers of water on a short-term or long-term basis. The City’s projected supply availability in this UWMP is based on existing water rights, contractual entitlements, recycled water production, and planned groundwater production. The City does not currently rely on additional short-term or long-term water transfers or exchanges to meet projected normal-year demands identified in this UWMP.

The City participates in limited regional exchange and mutual aid arrangements that may provide operational flexibility during emergencies or constrained supply conditions. The Whale Rock Commission, of which the City is a member agency, has an agreement with the City of Morro Bay that provides a framework for mutual aid during disruptions to water deliveries or lack of available water supplies. The City also has an agreement with San Luis Obispo County Service Area No. 10A allowing for the exchange of up to 50 acre-feet per year of Nacimiento water for water from Whale Rock Reservoir.

These agreements provide operational flexibility and emergency response options, but they are not assumed to increase the City’s projected long-term water supply availability in this UWMP. The City may evaluate future water transfer, exchange, or cooperative water management opportunities if they become available and are consistent with applicable water rights, contractual obligations, infrastructure capacity, treatment requirements, environmental requirements, and long-term water supply reliability objectives.

CHAPTER 7: WATER SERVICE RELIABILITY AND DROUGHT RISK

ASSESSMENT

7.1 Introduction
Chapter 7 evaluates the reliability of the City’s water supplies under the hydrologic conditions required by the UWMP Act. The chapter includes both long-term water service reliability analysis and near-term drought risk assessment.

Sections 7.4 through 7.6 evaluate long-term reliability under normal-year, single dry-year, and multiple dryyear conditions using the demand forecasts described in Chapter 4 and the long-term water supply planning values described in Chapter 6. These analyses evaluate whether the City’s existing and planned supplies are sufficient to meet projected demands through the UWMP planning horizon.

Section 7.7 presents the five-year drought risk assessment, which is a near-term operational reliability analysis supported by the City’s Water Projection Model. The five-year drought risk assessment evaluates whether available supplies are sufficient during the near-term five-year drought risk period using current or projected near-term conditions, including current reservoir storage, recent water use, current population estimates, seasonal demand patterns, source availability, infrastructure constraints, groundwater project status, recycled water availability, and dry-year assumptions.

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54 When conducting a drought risk assessment, if actual or projected conditions result in a water shortage, the City would implement the shortage response actions identified in the Water Shortage Contingency Plan, which is described in Chapter 8 and included as Appendix H.

7.2 Basis of Water Service Reliability Assessment
The City’s water service reliability analysis is based on projected water demands and projected water supply availability for each required planning scenario. Because Chapter 7 includes both long-term reliability analysis and near-term drought risk assessment, the City applies different methodologies based on the purpose of each analysis.

For the long-term reliability assessments presented in Sections 7.4 through 7.6, the City uses the long-term demand forecasts described in Chapter 4 and the long-term supply planning values described in Chapter

6. Long-term potable demand is based on the population methodology described in Section 3.6 and the City’s 117 gpcd planning value. Long-term potable supply availability is based on established sourcespecific planning values, including Nacimiento Reservoir contractual supply, the combined Salinas and Whale Rock Reservoir safe annual yield with the long-term siltation adjustment, and planned groundwater production when available. Recycled water is evaluated separately as a non-potable supply that offsets potable demand where recycled water service is available. This long-term method is consistent with the General Plan and WWE and is intentionally conservative. It is used to evaluate supply sufficiency many years into the future, when future population, customer water use, hydrologic conditions, regulatory requirements, infrastructure needs, climate conditions, and source availability may differ from current conditions. The long-term method therefore provides a conservative planning basis for General Plan consistency, infrastructure planning, and UWMP reliability analysis.

For the five-year drought risk assessment and upcoming single-year assessments, the City uses near-term operational reliability analysis. This analysis is supported by the Water Projection Model and uses current or projected near-term conditions, including reservoir storage, recent water use, current population estimates, seasonal demand patterns, source-specific availability, infrastructure constraints, groundwater project status, recycled water availability, and dry-year assumptions. This method is used because the purpose of the five-year drought risk assessment and annual assessments is to determine whether the City can meet expected near-term demands under reasonably anticipated operating conditions, not to evaluate General Plan buildout demand.

Separate forecasting methodologies are used because long-term planning and near-term operational analysis serve different purposes. Applying the General Plan demand methodology to near-term analyses could overstate expected customer demand by using buildout-oriented assumptions for a period when actual population, recent water use, and current operating conditions are known with greater certainty.

Conversely, relying only on current demand for long-term planning could understate future needs and would not provide the conservative basis needed for General Plan consistency and multi-decade water supply planning.

7.3 Water Year Type Characterization
The UWMP Act requires urban water suppliers to evaluate water service reliability under normal-year, single dry-year, and multiple dry-year conditions. For purposes of this UWMP, the City evaluates these conditions using the source-specific planning assumptions described in Chapter 6, including the safe annual yield analysis for Salinas and Whale Rock Reservoirs, Nacimiento Reservoir contractual supply reliability, planned groundwater availability, recycled water availability, and known infrastructure constraints.

Because the City’s supply portfolio is based primarily on stored surface water and stored groundwater supplies, availability is not characterized solely by selecting an average rainfall year or a single historical dry year. Instead, the City applies assumptions that reflect how each source is planned and operated to preserve supplies on a long-term basis. These assumptions are then applied to the UWMP’s required water year types as described below.

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55 • Normal year: A normal year represents typical hydrologic and operational conditions used to evaluate projected supply availability and demand. For the City, normal-year supplies are based on adopted planning assumptions for each source, including the combined Salinas and Whale Rock Reservoir safe annual yield, Nacimiento dependable yield, groundwater safe annual yield, and recycled water availability.
• Single dry year: A single dry year represents one year of reduced hydrologic supply availability.

For water suppliers with surface water systems, this often includes reduced runoff, reduced reservoir inflow, increased reliance on stored supplies, and the need to preserve reservoir reliability if dry conditions continue. For the City, these conditions are already reflected in the planning values used for its primary surface water supplies. The Salinas and Whale Rock Reservoir supply is based on safe annual yield modeling that evaluates the coordinated operation of the reservoirs through historical hydrologic conditions, including drought periods. Nacimiento Reservoir supply availability is based on the City’s contractual entitlement and prior dependable yield analyses that evaluated the reliability of that supply during drought conditions. Because these dry-year effects are already incorporated into the City’s surface water planning assumptions, the City does not apply a blanket additional dry-year reduction to all supplies for the single dry-year scenario. However, to support continued compliance with SGMA and avoid or minimize potential impacts to basin conditions and interconnected surface waters, the City applies a reduction of available supply from 700 AFY to 300 AFY to available groundwater supplies during the single dry-year scenario. • Multiple dry years: A multiple dry-year period represents five consecutive years of reduced hydrologic supply availability. For water suppliers with surface water systems, this often includes prolonged reductions in runoff and reservoir inflow, increased reliance on stored supplies, and a greater need to preserve long-term reservoir reliability. For the City, these conditions are already reflected in the planning values used for its primary surface water supplies. The Salinas and Whale Rock Reservoir supply is based on safe annual yield modeling that evaluates the coordinated operation of the reservoirs through historical drought periods, including extended drought conditions. Nacimiento Reservoir supply availability is based on the City’s contractual entitlement and prior dependable yield analyses that evaluated the reliability of that supply during drought conditions. Because these drought-related effects are already incorporated into the City’s surface water planning assumptions, the City does not apply a blanket additional dry-year reduction to all supplies for the multiple dry-year scenario. However, to support continued compliance with SGMA and avoid or minimize potential impacts to basin conditions and interconnected surface waters, the City applies increasing annual reductions to available groundwater supplies during multiple dryyear scenarios.

7.4 Normal-Year Water Service Reliability
Normal-year reliability compares projected water demand with projected available water supplies under expected non-drought planning conditions. The City’s normal-year potable supplies include Salinas Reservoir, Whale Rock Reservoir, Nacimiento Reservoir, and planned groundwater production. Recycled water is evaluated separately as a non-potable supply.

The City’s normal-year reliability analysis demonstrates that projected potable supplies are sufficient to meet projected potable demands through 2050, as shown in Table 7-1. The analysis also demonstrates that projected recycled water supplies are sufficient to meet projected recycled water demands through 2050, as show in Table 7-2.

TABLE 7-1: NORMAL-YEAR POTABLE WATER RELIABILITY
Planning Year Potable Supply
(acre-feet)
Potable Demand
(acre-feet)
Potable
Surplus/Deficit
(acre-feet)

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56 2030 10,592 7,068 3,524
2035 10,592 7,496 3,096
2040 10,592 7,879 2,713
2045 10,592 8,281 2,311
2050 10,592 8,703 1,889
Notes: Demand values are based on the Section 3.6 population methodology and the City’s 117 gpcd water demand planning value. Supply values are based on the long-term source availability and planning assumptions described in Chapter 6.

TABLE 7-2: NORMAL-YEAR NON-POTABLE RELIABILITY
Planning Year
Non-Potable
Supply (acrefeet)
Non-Potable
Demand
(acre-feet)
Non-Potable
Surplus/Deficit
(acre-feet)
2030 1,296 338 958
2035 1,296 388 908
2040 1,296 438 858
2045 1,296 488 808
2050 1,296 538 758
Notes:

7.5 Single Dry-Year Water Service Reliability
Single dry-year reliability evaluates the City’s ability to meet projected demands during one dry year. Dryyear conditions may reduce runoff, reservoir inflows, or available surface water supply. The City’s supply portfolio is designed to remain reliable under dry-year conditions through stored surface water supplies, Nacimiento water, planned groundwater production, recycled water offsets, and demand management measures as needed.

The City’s single dry-year analysis demonstrates that projected potable supplies are sufficient to meet projected potable demands through 2050. Projected recycled water supplies are also sufficient to meet projected recycled water demands through 2050, subject to the operational and regulatory considerations described in Chapter 6. Single Dry-Year projections for the UWMP planning horizon can be seen in Table 7-1 and Table 7-2.

TABLE 7-3: SINGLE DRY-YEAR POTABLE WATER RELIABILITY
Planning Year Potable Supply
(acre-feet)
Potable Demand
(acre-feet)
Potable
Surplus/Deficit
(acre-feet)
2030 10,192 7,068 3,124
2035 10,192 7,496 2,696
2040 10,192 7,879 2,313
2045 10,192 8,281 1,911
2050 10,192 8,703 1,489
Notes: Demand values are based on the Section 3.6 population methodology and the City’s 117 gpcd water demand planning value. Supply values are based on the long-term source availability and planning assumptions described in Chapter 6.

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57 TABLE 7-4: SINGLE DRY-YEAR NON-POTABLE WATER RELIABILITY Planning Year
Non-Potable
Supply (acrefeet)
Non-Potable
Demand
(acre-feet)
Non-Potable
Surplus/Deficit
(acre-feet)
2030 1,296 371 925
2035 1,296 426 870
2040 1,296 481 815
2045 1,296 536 760
2050 1,296 591 705
Notes:

7.6 Multiple Dry-Year Water Service Reliability
Multiple dry-year reliability evaluates the City’s ability to meet projected demands during five consecutive dry years. This analysis tests the City’s water supply portfolio under extended drought conditions and determines whether projected supplies are sufficient over a multi-year dry period.

The City’s surface water planning assumptions are intended to preserve reliability over multiple years.

Salinas and Whale Rock Reservoir supplies are based on safe annual yield modeling that evaluates reservoir operations over historical drought periods, including the extended 2006–2016 drought period.

Nacimiento supplies are based on the City’s contractual entitlement and reliability evaluations described in Chapter 6. Planned groundwater production and recycled water supplies provide additional diversification and operational flexibility, but their availability may vary under multiple dry-year conditions.

The City’s multiple dry-year analysis demonstrates that projected potable supplies are sufficient to meet projected potable demands through 2050, as shown in Table 7-5. Projected recycled water supplies are also sufficient to meet projected recycled water demands during the five-year dry sequence, as shown in Table 7-6.

Groundwater availability is adjusted in the multiple dry-year analysis to reflect groundwater basin management considerations and the City’s intent to avoid or minimize potential impacts to surface water flows and other groundwater sustainability plan sustainable management criteria. Under normal planning conditions, groundwater availability may be assumed at up to 700 acre-feet per year once groundwater is available. During multiple dry-year planning scenarios, assumed groundwater availability is reduced to volumes as low as 50 acre-feet per year. These reductions are reflected in the multiple dry-year reliability tables.

TABLE 7-5: MULTIPLE DRY-YEAR POTABLE WATER RELIABILITY
2030 2035 2040 2045 2050
First year
Supply totals 10,192 10,192 10,192 10,192 10,192
Demand totals 7,068 7,496 7,879 8,281 8,703
Surplus/Deficit 3,124 2,696 2,313 1,911 1,489
Second year
Supply totals 10,092 10,092 10,092 10,092 10,092
Demand totals 7,139 7,571 7,958 8,364 8,790
Surplus/Deficit 2,953 2,521 2,134 1,728 1,302
Third year
Supply totals 10,042 10,042 10,042 10,042 10,042
Demand totals 7,210 7,647 8,037 8,447 8,878
Surplus/Deficit 2,832 2,395 2,005 1,595 1,164
Fourth year Supply totals 9,992 9,992 9,992 9,992 9,992

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58 Demand totals 7,283 7,724 8,118 8,532 8,967
Surplus/Deficit 2,709 2,268 1,874 1,460 1,025
Fifth year
Supply totals 9,942 9,942 9,942 9,942 9,942
Demand totals 7,355 7,801 8,199 8,617 9,056
Surplus/Deficit 2,587 2,141 1,743 1,325 886
Notes: Demand values are based on the Section 3.6 population methodology and the City’s 117 gpcd water demand planning value. Supply values are based on the long-term source availability and planning assumptions described in Chapter 6.

TABLE 7-6: MULTIPLE DRY-YEAR NON-POTABLE WATER RELIABILITY 2030 2035 2040 2045 2050
First year
Supply totals 1,296 1,296 1,296 1,296 1,296
Demand totals 371 426 481 536 591
Surplus/Deficit 925 870 815 760 705
Second year
Supply totals 1,296 1,296 1,296 1,296 1,296
Demand totals 382 437 492 547 602
Surplus/Deficit 914 859 804 749 694
Third year
Supply totals 1,296 1,296 1,296 1,296 1,296
Demand totals 393 448 503 558 613
Surplus/Deficit 903 848 793 738 683
Fourth year
Supply totals 1,296 1,296 1,296 1,296 1,296
Demand totals 404 459 514 569 624
Surplus/Deficit 892 837 782 727 672
Fifth year
Supply totals 1,296 1,296 1,296 1,296 1,296
Demand totals 415 470 525 580 635
Surplus/Deficit 881 826 771 716 661
Notes:

7.7 Five-Year Drought Risk Assessment
The UWMP Act requires urban water suppliers to include a drought risk assessment that evaluates water supply reliability for a five-consecutive-year drought period. For the 2025 UWMP, the five-year drought risk assessment evaluates the City’s ability to meet projected demands during the near-term period from FY 2026-27 through FY 2030-31.

The five-year drought risk assessment is a near-term operational reliability analysis. Unlike the long-term reliability tables presented in Sections 7.4 through 7.6, the five-year drought risk assessment does not use General Plan buildout demand assumptions or the City’s 117 gpcd long-term water demand planning value to estimate customer demand. Instead, the City uses its Water Projection Model and current or projected near-term conditions to evaluate whether available supplies are sufficient during the five-year drought risk period. The Water Projection Model evaluates how current and projected near-term conditions may affect the City’s ability to meet demands during the five-year drought risk period. Model inputs may include current reservoir storage volumes, recent potable water use, current population estimates, recent seasonal demand patterns, source-specific availability, dry-year hydrologic assumptions, Nacimiento conveyance assumptions, groundwater project completion timing, recycled water availability, infrastructure constraints, and applicable regulatory or operational limitations. The model provides an assessment of near-term water supply availability and helps determine whether a shortage is anticipated and whether WSCP response actions may be needed.

The five-year drought risk assessment considers historical drought hydrology, current and projected nearterm supply conditions, and locally applicable climate-related factors that could affect supplies or demands during the assessment period. Climate change may affect the City’s water supplies through changes in

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59 precipitation timing, runoff efficiency, reservoir inflows, evaporation, drought duration and severity, wildfire risk, watershed conditions, and source water quality. Climate-related demand effects may include changes in seasonal irrigation demand, evapotranspiration, and customer water use patterns. These considerations are incorporated qualitatively through the City’s selection of dry-year assumptions, evaluation of current reservoir storage and source availability, assessment of infrastructure and operational constraints, and ongoing use of the Water Projection Model.

The City does not apply a separate numerical climate change adjustment to projected demands or supplies in the five-year drought risk assessment. Instead, the assessment uses current and projected near-term conditions, drought-informed hydrologic assumptions, known infrastructure constraints, and source-specific reliability information to evaluate potential shortage conditions.

For purposes of this five-year drought risk assessment, potable and non-potable supplies are evaluated separately. Potable demands are compared against potable supplies available from Salinas Reservoir, Whale Rock Reservoir, Nacimiento Reservoir, and planned groundwater production, as applicable during the assessment period. Non-potable demands are compared against recycled water supplies available for approved non-potable uses. Recycled water offsets potable demand where recycled water service is available, feasible, and authorized, but it is not assumed to meet potable demands.

The five-year drought risk assessment incorporates known near-term conditions that may affect source availability during the assessment period, including temporary Nacimiento transmission system conveyance constraints, the anticipated timing of permanent Nacimiento pipeline repairs, the expected timing of groundwater treatment and extraction facilities coming online, and other operational or infrastructure limitations. As these conditions change, the City will reevaluate near-term supply availability through the annual water supply and demand assessment process and implement the WSCP as needed.

As shown in Table 7-7 and Table 7-8, the City’s projected near-term supplies are sufficient to meet projected potable and non-potable demands during the five-year drought risk assessment period. Based on the assumptions used in this assessment, the City does not anticipate a water shortage during the five-year drought risk assessment period. If actual conditions differ from the assumptions used in this assessment, including changes in reservoir storage, hydrology, infrastructure availability, water quality, treatment capacity, regulatory requirements, or customer demand, the City will re-evaluate water supply conditions through its annual water supply and demand assessment process and implement the WSCP as needed.

Based on the assumptions used in this assessment, the City has sufficient supplies to meet projected demands during the Five-Year Drought Risk Assessment period. Near-term reliability is supported by the City’s diversified supply portfolio, local reservoir supplies, planned groundwater restoration, and recycled water offsets. Drought Risk Assessment details for potable water and recycled water can be found in Table 7-7 and Table 7-8.

TABLE 7-7: FIVE-YEAR DROUGHT RISK ASSESSMENT - POTABLE WATER Reporting Year Potable Demand Potable Supply Potable Surplus / Shortage
FY 2026-27 5,355 6,481 1,126
FY 2027-28 5,451 10,357 4,906
FY 2028-29 5,506 10,307 4,801
FY 2029-30 5,561 10,257 4,696
FY 2030-31 5,616 10,207 4,591
Notes:

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2025 Urban Water Management Plan
60 TABLE 7-8: FIVE-YEAR DROUGHT RISK ASSESSMENT - NON-POTABLE WATER Reporting Year Non-Potable Demand Non-Potable Supply Non-Potable Surplus / Shortage
FY 2026-27 306 1,296 990
FY 2027-28 348 1,296 948
FY 2028-29 359 1,296 937
FY 2029-30 370 1,296 926
FY 2030-31 381 1,296 915
Notes:

7.8 Reliability Findings and Relationship to the WSCP
The water service reliability analysis demonstrates that the City’s projected potable supplies are sufficient to meet projected potable demands under normal-year, single dry-year, and multiple dry-year conditions through 2050. The analysis also demonstrates that projected recycled water supplies are sufficient to meet projected recycled water demands through 2050.

The City’s reliability is supported by a diversified supply portfolio that includes local surface water supplies, planned groundwater production, and recycled water. The City’s use of conservative planning assumptions, including the safe annual yield for Salinas and Whale Rock Reservoirs, the long-term siltation planning adjustment, drought-representative modeling, source-specific groundwater adjustments, and the separate evaluation of recycled water as a non-potable supply, provides a reasonable basis for evaluating long-term reliability.

Although this chapter demonstrates projected supply sufficiency, actual conditions may differ from the assumptions used in the UWMP. Potential causes of reduced supply availability include extended drought, infrastructure failure, wildfire or watershed disturbance, water quality impacts, regulatory changes, treatment or conveyance limitations, groundwater production delays, groundwater basin management constraints, reduced recycled water availability, or demand conditions that differ from projections. If such conditions result in a projected or actual shortage, the City would implement the WSCP described in Chapter 8.

The WSCP establishes the City’s shortage response framework, including shortage stages, demand reduction actions, supply augmentation options, communication protocols, monitoring and reporting procedures, and enforcement mechanisms. The WSCP allows the City to respond to changing conditions while continuing to protect public health, safety, and essential water uses.

CHAPTER 8: WATER SHORTAGE CONTINGENCY PLANNING &

EMERGENCY SUPPLY RESILIENCY

8.1 Introduction
The City’s Water Shortage Contingency Plan (WSCP) provides the framework for identifying, declaring, responding to, and recovering from water shortage conditions. A water shortage may result from drought, infrastructure failure, seismic damage, wildfire impacts, water quality issues, regulatory limitations, power outages, supply interruption, or other emergency conditions that affect the City’s ability to access, convey, treat, or deliver water.

The UWMP Act requires urban water suppliers to prepare a WSCP that includes procedures for conducting

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61 an annual water supply and demand assessment, six standard water shortage levels, shortage response actions, communication protocols, monitoring and reporting procedures, enforcement provisions, and other actions necessary to address shortage conditions. The WSCP is adopted in coordination with the UWMP and is included as an appendix to this Plan. Because the WSCP is intended to guide the City’s response to actual or projected water shortage conditions, it may be reviewed separately from the UWMP and updated over time as needed to reflect changes in State requirements, DWR guidance, City policy, water supply conditions, system operations, or implementation experience.

The City’s WSCP is intended to function as an operational response plan. It does not replace the long-term water supply reliability analysis presented in Chapter 7. Instead, the WSCP provides the response framework the City would use if actual or projected near-term conditions indicate that available supplies may be insufficient to meet expected demands. WSCP implementation is informed by near-term operational reliability analysis, including current storage, recent water use, source availability, infrastructure constraints, and the City’s Water Projection Model.

8.2 Potential Causes of Water Shortage Conditions
Water shortage conditions may result from a range of hydrologic, operational, infrastructure, regulatory, or emergency conditions. While drought is often the primary long-term water supply reliability concern, the City’s water supply availability could also be affected by conditions that limit the City’s ability to access, convey, treat, or distribute otherwise available supplies.

Potential causes of water shortage conditions may include, but are not limited to:
• Prolonged drought or reduced runoff into surface water reservoirs; • Damage to raw water transmission pipelines, pump stations, or other conveyance facilities; • Seismic events that damage dams, reservoirs, pipelines, tanks, pump stations, treatment facilities, or distribution system infrastructure;
• Wildfire impacts to watersheds, reservoir water quality, or treatment plant operations; • Water quality conditions that reduce source availability or treatment capacity; • Regulatory requirements affecting diversions, releases, discharges, or source operations; • Power outages or energy supply constraints affecting pumping, treatment, or distribution; • Treatment plant or distribution system failures; and
• Emergency conditions that increase water demand.

Because the City relies on multiple surface water reservoirs, raw water conveyance facilities, treatment infrastructure, storage facilities, distribution system assets, recycled water facilities, and planned groundwater infrastructure, water shortage planning must consider both the amount of water available from each source and the City’s ability to physically deliver that water to customers. The WSCP provides the City’s staged response framework for addressing actual or projected shortage conditions, regardless of whether the shortage is caused by drought, infrastructure limitations, emergency conditions, or another supply interruption.

8.2.1 Seismic Risk Assessment and Mitigation
California Water Code section 10632.5(a) requires UWMPs to include a seismic risk assessment and mitigation plan to assess and mitigate a water system’s seismic vulnerabilities. Pursuant to California Water Code section 10632.5(c), an adopted Local Hazard Mitigation Plan or Multi-Jurisdictional Hazard Mitigation Plan may be incorporated into a UWMP to satisfy this requirement if the plan addresses seismic risk.

In coordination with the County of San Luis Obispo and participating local agencies, the 2025-2030 San Luis Obispo County Multi-Jurisdictional Hazard Mitigation Plan (MJHMP) was developed to assess regional hazards, vulnerabilities, and mitigation strategies associated with natural and human-caused disasters. The City of San Luis Obispo participated in the development of the MJHMP and incorporates the plan by reference into this UWMP for purposes of complying with California Water Code section 10632.5.

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2025 Urban Water Management Plan
62 The MJHMP evaluates earthquake hazards, liquefaction susceptibility, critical facility vulnerabilities, utility system impacts, and infrastructure mitigation strategies applicable to the City and surrounding region. The MJHMP also identifies potential impacts to utility infrastructure, including water transmission pipelines, storage facilities, pump stations, treatment facilities, and related systems that could be affected by seismic activity. Accordingly, the MJHMP also identifies mitigation measures intended to improve infrastructure resilience and emergency preparedness, including capital improvements, emergency response coordination, infrastructure assessments, redundancy planning, and continued incorporation of seismic considerations into facility design and maintenance activities. The City uses information contained in the MJHMP to support emergency preparedness planning, capital improvement prioritization, infrastructure resiliency efforts, and interagency coordination during emergency response and recovery activities.

The City’s water system also benefits from operational flexibility associated with multiple water supply sources, interconnected transmission facilities, emergency storage, backup power capabilities, mutual aid coordination, and emergency response procedures maintained through the Utilities Branch’s Emergency Operations Plan and related emergency response programs. These measures support the City’s ability to prepare for, respond to, and recover from seismic events and other emergency conditions that could affect water service.

The 2025-2030 San Luis Obispo County MJHMP is incorporated by reference into this UWMP and may be amended or updated independently of the UWMP process in accordance with applicable federal, state, and local requirements.

8.3 City Water Shortage Contingency Plan
The City’s WSCP is included as Appendix H to the 2025 UWMP. The WSCP establishes the procedures and response actions the City would use to address water shortage conditions. It includes the City’s annual assessment process, shortage stage framework, shortage response actions, communication procedures, enforcement provisions, revenue and expenditure considerations, monitoring and reporting procedures, and procedures for responding to catastrophic supply interruptions.

The WSCP includes six shortage stages that correspond to progressively increasing levels of water supply shortage. These stages are intended to provide a structured framework for escalating response actions as supply conditions worsen. The stages are generally aligned with shortage levels of up to 10 percent, 10 to 20 percent, 20 to 30 percent, 30 to 40 percent, 40 to 50 percent, and greater than 50 percent. The specific response actions implemented during a shortage would depend on the cause, severity, duration, timing, and expected progression of the shortage.

The City evaluates near-term water supply conditions through its annual water supply and demand assessment process. This assessment considers current and projected near-term demands, sourcespecific supply availability, reservoir storage, hydrologic conditions, infrastructure constraints, treatment and conveyance limitations, recycled water availability, groundwater project status, and other relevant operational conditions. The assessment is supported by the City’s Water Projection Model, which helps evaluate the City’s ability to meet expected demands under actual or projected near-term conditions.

If the annual assessment or another operational evaluation indicates that available supplies may be insufficient to meet expected demands, City staff would evaluate the appropriate WSCP stage and recommended response actions. The City Council would declare the applicable water shortage stage and authorize implementation of specific shortage response actions through resolution, ordinance, or other appropriate action. The City may also implement emergency response actions as needed if a sudden supply interruption, infrastructure failure, water quality issue, or other emergency required immediate action.

WSCP response actions may include public outreach and education, voluntary or mandatory conservation measures, outdoor irrigation restrictions, restrictions on water waste, limitations on certain discretionary uses of water, expanded monitoring and reporting, increased enforcement, drought rates or financial

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63 response measures, and other actions necessary to reduce demand or protect public health and safety.

The City may tailor response actions to the specific circumstances of a shortage and is not required to implement every action listed in the WSCP during every shortage event.

The WSCP is intended to remain flexible and implementable. Because water shortages may result from different causes, the City must retain the ability to adjust response actions based on the nature of the shortage. For example, a drought-related shortage may require sustained demand reduction over an extended period, while an infrastructure failure may require targeted short-term restrictions, emergency repairs, temporary supply measures, or localized operational changes. The WSCP provides the framework for these decisions while preserving City Council discretion to respond to actual conditions.

8.4 Water Shortage Contingency Plan Adoption, Submittal, and Availability The City’s WSCP was adopted by the City Council alongside the 2025 UWMP on June 16, 2026 by Resolution No.______. The adopted WSCP is included as Appendix H to this UWMP.

Following adoption, the City will submit the WSCP to DWR together with the adopted UWMP through the required online submittal process. The City will also make the adopted WSCP available for public review on the City’s website and at applicable City offices, consistent with UWMP Act requirements.

Because the WSCP may need to be updated more frequently than the UWMP, the City may amend the WSCP independently of the UWMP if needed to respond to changes in State law, DWR guidance, City policy, water supply conditions, system operations, emergency response procedures, or implementation experience. Any future amendment to the WSCP would be completed in accordance with applicable legal requirements, including public noticing, City Council consideration, and submittal to DWR as required.

CHAPTER 9: DEMAND MANAGEMENT MEASURES

9.1 Introduction
Demand management measures are water conservation programs, policies, incentives, operational practices, and regulatory measures that reduce water waste and promote the reasonable and efficient use of available water supplies. Demand management is an important component of the City’s long-term water supply strategy because it helps reduce potable water demands, improve drought resilience, support compliance with State water use efficiency requirements, and extend the reliability of existing supplies.

The City’s water conservation program supports both long-term water supply reliability and day-to-day customer water use efficiency. The program includes operational measures such as metering, billing data review, Advanced Metering Infrastructure, water loss control, and recycled water use; customer-oriented measures such as outreach, audits, rebates, complimentary devices, and landscape water budgets; and regulatory measures such as water waste enforcement, plumbing retrofit requirements, Model Water Efficient Landscape Ordinance implementation, Urban Water Use Objective reporting, and UWMP and Water Shortage Contingency Plan compliance.

The City’s demand management measures are guided in part by the City’s 2023 Water Conservation and Efficiency Plan. That plan provides a proactive framework for reducing water demand, improving water use efficiency, reducing water loss and waste, and supporting responsible land management practices. The 2023 plan distinguishes these proactive conservation efforts from the City’s Water Shortage Contingency Plan, which identifies actions taken in response to drought or other shortage conditions.

This chapter describes the City’s demand management measures and summarizes the nature and extent of implementation during the 2021 through 2025 UWMP reporting period, consistent with Water Code section 10631(e). The measures described in this chapter support the water demand projections presented in Chapter 4, the water supply reliability analysis presented in Chapter 7, and the shortage response

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64 framework described in Chapter 8.

9.2 Water Conservation Program Goals and Objectives
The City’s water conservation program is intended to support reliable water service, reduce unnecessary water use, comply with State and federal requirements, and promote responsible water use practices throughout the community. The City’s 2023 Water Conservation and Efficiency Plan identifies five primary objectives:

1. Develop cost-effective water conservation measures that maximize opportunities to meet the future water needs of the community;

2. Offset or delay the need to construct additional water supplies or upsize treatment and distribution infrastructure;

3. Offset or reduce ratepayer costs associated with the treatment and delivery of safe drinking water and the treatment of wastewater;

4. Meet applicable State and federal water conservation mandates; and

5. Foster environmental stewardship through responsible and innovative water use practices.

These objectives reflect the City’s approach to conservation as both a long-term water supply reliability strategy and a practical tool for improving day-to-day water use efficiency. By reducing inefficient water use and improving the City’s ability to understand customer demand patterns, the City can better manage existing supplies, improve system resiliency, and support sustainable community growth.

9.3 Historical Conservation Efforts
Water conservation has been a core component of the City’s water management strategy for decades.

Conservation was first referenced in the City’s water management policies in 1973, and in 1985 the City adopted the Annual Water Operational Plan policy, which identified conservation as a tool for extending available supplies during projected water shortages. Since that time, conservation has evolved from a primarily drought-response measure into an ongoing water resource management strategy that supports long-term supply reliability, infrastructure planning, regulatory compliance, and responsible water use.

The City’s conservation program has historically included a combination of regulatory requirements, customer assistance programs, operational practices, and public education. These efforts have included water waste prohibitions, water use surveys and audits, plumbing fixture replacement requirements, public outreach, conservation-oriented pricing, recycled water use, landscape water efficiency standards, water loss auditing, meter replacement, and customer assistance programs. Together, these measures have helped reduce inefficient water use while allowing the City to continue meeting community water needs.

The effectiveness of the City’s long-term conservation efforts is reflected in the City’s water use trends. The City’s 2023 Water Conservation and Efficiency Plan notes that total water demand has not increased at the same rate as population growth, and that community-wide water use declined from a high of approximately 182 gallons per capita per day in 1987 to approximately 92 gallons per capita per day in FY 2023. The 2023 Water Conservation and Efficiency Plan received Platinum recognition from the Alliance for Water Efficiency, the highest recognition level available, reflecting the City’s continued commitment to comprehensive and forward-looking conservation planning.

This history demonstrates that conservation is not only a temporary response to drought or shortage conditions. For the City, conservation functions as a continuing water supply reliability strategy by reducing avoidable demand, preserving stored supplies, delaying or reducing the need for new infrastructure, supporting regulatory compliance, and helping customers use water efficiently under both normal and dryyear conditions.

9.4 Demand Management Measure Implementation (2021-2025) The UWMP Act requires retail urban water suppliers to describe the nature and extent of demand

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2025 Urban Water Management Plan
65 management measures implemented during the prior five years. For the 2025 UWMP, this reporting period covers 2021 through 2025. The required demand management measure categories include water waste prevention ordinances, metering, consumption-based pricing, public education and outreach, programs to assess and manage distribution system losses, water conservation program coordination and staffing support, and other significant demand management measures.

During the 2021 through 2025 reporting period, the City continued implementing a broad conservation program intended to reduce water waste, improve customer water use efficiency, support regulatory compliance, and maintain long-term water supply reliability. These efforts included ongoing water waste enforcement, customer water use reviews, public outreach, recycled water program management, consumption-based rates, landscape efficiency review, water loss auditing, meter replacement, and implementation planning for Advanced Metering Infrastructure.

The City also advanced programs to prepare for new State water use efficiency requirements, including Urban Water Use Objective reporting, commercial, industrial, and institutional performance measures, dedicated irrigation meter tracking, large landscape water budgets, and future non-functional turf implementation. These efforts are part of the State’s broader Making Conservation a California Way of Life framework and are expected to shape the City’s conservation program over the next UWMP cycle.

The City’s 2023 Water Conservation and Efficiency Plan provided a more detailed evaluation of long-term conservation measures using the Alliance for Water Efficiency Conservation Tracker Tool. The plan evaluated potential water savings, costs, staffing needs, and customer participation opportunities, and identified a conservation program intended to maximize practical water savings using available funding and staff resources. The City’s subsequent conservation program planning has focused on implementation of selected measures, refinement of conservation review methods, rebate program adjustments, Waterfluence landscape budgets, AMI rollout, land-based demand projections, MWELO reporting, and preparation for UWUO and water loss reporting.

TABLE 9-1: DEMAND MANAGEMENT MEASURE IMPLEMENTATION SUMMARY (2021-2025) Demand Management
Measure Implementation During 2021-2025 Planned Continuation Water Waste Prohibition
Continued enforcement of water waste prohibitions
and response to suspected leaks, runoff, and
inefficient use.

Continue; update
procedures as needed.

Metering and AMI Continued monthly metering and billing; advanced phased AMI implementation.

Continue AMI rollout and
customer data
improvements.

Consumption-Based Pricing
Continued use of metered, consumption-based
water rates developed through cost-of-service
principles.

Continue future cost-ofservice review and rate
updates.

Public Education and
Outreach
Continued use of website information, direct
customer communication, public outreach,
conservation messaging, and program promotion.

Continue and tailor
outreach for AMI, CII,
UWUO, and nonfunctional turf.

Distribution System Loss
Reduction
Continued annual water loss audits, infrastructure
replacement, meter replacement, leak detection,
and water loss control activities.

Continue and integrate
AMI data as available.

Program Coordination and
Staffing
Continued conservation program coordination
across Water Resources, Utility Billing, Water
Distribution, and Planning sections/functions.

Continue coordinated
implementation and
reporting.

Other Significant DMMs
Continued recycled water program, rebates,
complimentary devices, customer audits,
plumbing retrofit, MWELO, and landscape water
budgets.

Continue and refine
based on costeffectiveness,
participation, and
regulatory needs.

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2025 Urban Water Management Plan
66 9.5 Water Waste Prevention Ordinances
The City’s water waste prevention requirements are a core component of its demand management program. Water waste prevention helps reduce unnecessary demand, supports responsible use of potable supplies, and provides the City with a regulatory mechanism to respond to inefficient or unreasonable water use.

The City’s Municipal Code prohibits water waste, including waste caused by leaks, faulty fixtures, excessive irrigation, and runoff. City staff respond to reports of water waste, review potential violations, conduct field inspections when needed, and work with customers to correct inefficient or wasteful water use. Water waste response is intended to achieve correction through education and customer assistance whenever practical, while retaining enforcement authority when voluntary compliance is not achieved.

The City’s water waste regulations also support implementation of the City’s WSCP during water shortage conditions. While water waste prohibitions apply during normal conditions, additional restrictions may be implemented during declared shortage stages to reduce demand and protect available supplies.

9.6 Metering, Billing, and Advanced Metering Infrastructure The City meters potable and non-potable water service connections and uses metered consumption data for billing, customer service, water conservation, water loss auditing, and demand forecasting. Metering supports conservation by linking water use to customer billing and by providing the data needed to identify leaks, high-use accounts, and unusual consumption patterns. The City also meters water supply sources, including surface water, groundwater, and recycled water sources, which supports system-wide water accounting and water loss analysis.

The City reads and bills meters monthly. Monthly billing data provides a regular source of customer consumption information and allows the City to identify potential leaks or abnormal consumption through routine billing and consumption reviews.

The City has begun implementing Advanced Metering Infrastructure (AMI) to improve water use monitoring, leak detection, customer service, and demand management. AMI will provide more timely and granular water use data, improve the City’s ability to identify continuous use and potential leaks, reduce inefficiencies associated with manual meter reading, and provide customers with better access to water use information.

It is anticipated that the addition of AMI capabilities will result in significant behavioral changes to water use within a customer’s home due to added oversight and awareness by water users.

As of 2025, approximately 5,000 meters had been equipped with radio communication endpoints as part of the City’s phased transition to a full AMI system, which is anticipated to be completed in 2028.

9.7 Conservation Pricing and Water Rate Structure
The City uses metered, consumption-based water rates for monthly water and sewer billings. Consumptionbased rates support water use efficiency by charging customers based on the amount of water used and by reinforcing the relationship between water use and the total cost of water service. The City’s water rates are developed through cost-of-service analysis and adopted through applicable public review and approval processes. Water rate setting must be consistent with cost-of-service requirements and applicable law, including Proposition 218. The City will continue to evaluate water rates through future cost-of-service studies to ensure that rates recover the cost of providing water service, remain legally defensible, and support efficient water use.

9.8 Public Education, Outreach, and Technical Assistance Public education and outreach are important tools for promoting water conservation, preventing water waste, and helping customers understand how to use water efficiently. The City has used public education and outreach to support conservation since the 1970s. Public outreach is used to support both ongoing conservation and implementation of new conservation-related regulatory requirements. During normal

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2025 Urban Water Management Plan
67 conditions, outreach may focus on efficient irrigation, leak detection, fixture efficiency, recycled water, landscape efficiency, rebates, complimentary devices, and responsible water use. During water shortage conditions, outreach may also include information about shortage stages, restrictions, enforcement, conservation targets, and available customer assistance.

The City’s outreach methods include website updates, City news articles, e-notifications, attendance at local events, informational materials, newsletters, social media advertising, welcome emails for new customers, billing inserts, online how-to videos, direct mail campaigns, and meetings with business groups and homeowners associations. The City is also expanding outreach to support commercial, industrial, and institutional water use efficiency. Planned and ongoing efforts include contacting high-use CII customers, identifying large landscapes, providing information about rebates and complimentary devices, and directing customers to irrigation scheduling training and water efficiency resources.

9.9 Programs to Assess and Manage Distribution System Losses The City has completed annual AWWA water loss audits since 2009 and conducts annual water loss audits and implements programs to reduce real and apparent losses within the potable water distribution system.

Water loss management supports water supply reliability by reducing avoidable losses, improving system efficiency, and helping prioritize infrastructure replacement and maintenance.

The City’s water loss control efforts include service line replacement, meter replacement, valve exercising to ensure effective system isolation during emergency leak repairs, capital project planning and delivery, acoustic leak detection, meter testing and calibration, and regularly scheduled billing audits.

The City will continue to reduce real and apparent losses through the measures outlined above and through expansion of its AMI infrastructure. Chapter 4 provides additional information regarding the City’s reported distribution system water loss.

9.10 Water Conservation Program Coordination and Staffing The City’s demand management measures are implemented through coordination among multiple Utilities work groups. Water Resources staff coordinate conservation planning, customer outreach, water waste response, conservation reviews, regulatory reporting, MWELO support, rebate and complimentary device programs, recycled water coordination, and long-term demand management planning. Utility Billing supports meter reading, billing review, customer account data, and customer communication. Water Distribution supports meter replacement, AMI implementation, leak detection, water loss control, valve exercising, and infrastructure maintenance.

The City’s Water Resources section, which leads the water conservation programs, is staffed by the Water Resources Program Manager, Water Conservation Specialist, Water Resource Technician, Recycled Water Specialist. Program responsibilities include UWMP and WSCP work, water supply and demand assessments, conservation reporting, UWUO work, water loss reporting, AMI coordination, MWELO reviews, rebate program administration, conservation reviews, public outreach, plumbing retrofit reviews, complimentary devices, water waste violations, Waterfluence budget development, and recycled water program implementation.

This coordinated staffing approach allows the City to connect customer-facing conservation programs with utility operations, billing, recycled water management, regulatory compliance, and long-term planning. The City may also use professional services, regional partnerships, or consultant support for specialized program needs such as land-based demand projections, outreach campaigns, irrigation system training, water loss validation, regulatory reporting, or conservation program evaluation.

9.11 Other Significant Demand Management Measures
In addition to the demand management measure categories described above, the City implements other programs that have a significant effect on water use and long-term water supply reliability, as noted below.

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2025 Urban Water Management Plan
68 9.11.1 Recycled Water Use
Recycled water offsets potable water use for approved non-potable applications and is an important component of the City’s demand management strategy. The City has used recycled water as part of its water supply portfolio since 2006. Recycled water is used primarily for landscape irrigation and construction water, and it provides a local, non-potable supply that is less dependent on surface reservoir inflows than the City’s potable surface water supplies. The City serves recycled water to over 50 recycled water users in the City. Each site is required to have a site supervisor who receives training and completes quarterly reports identifying water waste runoff and system deficiencies. In total, recycled water accounts for approximately five percent of the City’s water demand each year, offsetting water demand from local reservoirs.

9.11.2 Conservation Reviews, Audits, and Customer Support The City provides water conservation-related assistance to residential and non-residential customers who have high water use, suspected leaks, water waste violations, or an interest in reducing water consumption.

Staff may review historical water use, evaluate property conditions, confirm meter functionality, identify potential leaks, review irrigation practices, and provide information on low-flow fixtures and other water saving opportunities.

Staff typically attempt to work with customers by phone or email first after discovering abnormal water use at a property. If staff are unable to contact the customer, staff may conduct a site visit and make contact in person or leave a door hanger if unable to make personal contact. The City’s newer conservation program planning efforts include streamlining monthly conservation reviews through automated calls or pre-set emails, proactively providing monthly water use data to certain buildings and large landscapes, and annually contacting or scheduling site visits with high-use commercial customers. These contacts may include information about high-use status, current rebates, complimentary items, cost-effectiveness tools, and irrigation scheduling training.

9.11.3 Complimentary Devices and Rebate Programs
The City provides complimentary water conservation devices to help customers reduce inefficient water use. Complimentary devices include items such as low-flow showerheads, faucet aerators, flow meter bags, five-minute shower timers, dish squeegees, leak detection dye tablets, hose nozzles, soil moisture meters, water conservation posters, and lawn signs.

Additionally, the City uses rebates and financial incentives to encourage customers to replace inefficient fixtures, equipment, irrigation systems, or other water-using devices with more efficient alternatives. In 2022, the City Council authorized $30,000 to launch an updated rebate program. Beginning in 2023, the City offered rebates for high-efficiency toilets and urinals, large landscape smart irrigation controllers, and water-efficient restaurant dipper wells. Rebate funding was allocated among single-family residential, multifamily residential, and CII account holders to support equitable access to program funds. For a period the City also entered into a partnership with Rachio through the California Water Efficiency Partnership to offer discounted smart irrigation controllers to single-family residential customers.

The City’s plumbing retrofit program has been in place since the 1990s. This program has helped to create long-term indoor water savings by requiring inefficient fixtures to be replaced over time. The City adopted plumbing retrofit regulations in 1992 requiring existing residential and CII structures to be retrofitted with low-water-use plumbing fixtures upon sale, change of use, or expansion of use. The program was most recently amended on December 7, 2021, to require indoor toilets, faucets, showerheads, and urinals to meet California Civil Code section 1101.3. The City documents the use of this program through an online mapping tool showing properties certified as having low-flow fixtures. This program has reduced the City’s long-term water demand by an estimated 1,500 acre-feet per year since its inception.