2025 Urban Water
Management Plan
Public Draft
Part 2 Chapter 5
APRIL 2026 RIALTO
RIALTO
2025 Urban Water
Management Plan Public
Draft
APRIL 2026
Prepared by Water Systems Consulting, Inc
ACKNOWLEDGEMENTS
The 2025 Urban Water Management Plan Public Draft was prepared by Water Systems Consulting, Inc. and Blua Consulting, LLC. The primary authors are listed below.
Laine Carlson, PE
Ariana Lopez
Aaron Morland, PE
Patricia Parks, PE
Madeline Blua
Water Systems Consulting, Inc. would like to acknowledge the significant contributions of the City of Rialto. The primary contributors are listed below.
Toyasha Sebbag
Jason Pivovaroff, Dopudja & Wells
Rialto Water Services, as Operated by Veolia North America
Table of Contents
2025 Urban Water Management Plan Public Draft | i
TABLE OF CONTENTS
5 City of Rialto ................................ ................................ ................................ .................... 5-1
5.1 System Description ................................ ................................ ................................ ... 5-2
5.2 Water Use ................................ ................................ ................................ ................. 5-4
5.3 SBX7-7 Compliance & Future Water Use Efficiency Requirements ........................ 5-14
5.4 Water Supply ................................ ................................ ................................ .......... 5-15
5.5 Water Service Reliability Assessment ................................ ................................ ..... 5-27
5.6 Drought Risk Assessment ................................ ................................ ....................... 5-31
5.7 Water Shortage Contingency Plan ................................ ................................ .......... 5-32
5.8 Demand Management Measures ................................ ................................ ............ 5-33
5.9 Adoption, Submittal and Implementation ................................ ................................ . 5-35
List of Figures
2025 Urban Water Management Plan Public Draft | ii
LIST OF FIGURES
Figure 5-1: City of Rialto Water Service Area Map ................................ ................................ .. 5-3 Figure 5-2. City of Rialto 2021-2025 Water Consumption by Customer Class ......................... 5-6 Figure 5-3: City of Rialto Historic and Projected Demand (AFY) ................................ ........... 5-12 Figure 5-4: City of Rialto Projected Supply (AFY) ................................ ................................ .. 5-25 List of Tables
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LIST OF TABLES
Table 5-1: DWR 3-1R Current and Projected Population ................................ ........................ 5-4 Table 5-2: City of Rialto 2021-2025 Connections by Customer Class ................................ ..... 5-5 Table 5-3: 2021-2025 Actual Water Use (AFY) ................................ ................................ ....... 5-6 Table 5-4: DWR 4-5R Month Water Loss Audit Reporting ................................ ....................... 5-7 Table 5-5: DWR 4-6R Progress Towards 2028 Water Loss Standard ................................ ..... 5-9 Table 5-6. Growth Rates used to Develop Projected Demand ................................ .............. 5-11 Table 5-7: DWR 4-2R Projected Demands for Water (AF) ................................ .................... 5-11 Table 5-8: DWR 4-3R Inclusion in Water Use Projections ................................ ..................... 5-13 Table 5-9: SBX7-7 2020 Target Progress ................................ ................................ ............. 5-14 Table 5-10: DWR 6-1R Groundwater Pumped Last Five Years (AF) ................................ ..... 5-18 Table 5-11: DWR 6-2R Wastewater Collected within Service Area in 2025 (AF) ................... 5-20 Table 5-12: DWR 6-3R Wastewater Treatment and Outcomes within UWMP Service Area in 2025 ................................ ................................ ................................ ................................ ...... 5-21 Table 5-13: DWR 6-8R Actual Water Supplies in 2025 (AF)................................ .................. 5-23 Table 5-14: DWR 6-9R Projected Water Supplies (AF) ................................ ......................... 5-24 Table 5-15: DWR 7-2R Normal Year Supply and Demand Comparison (AFY) ...................... 5-25 Table 5-16: DWR 7-1R Basis of Water Year Data ................................ ................................ . 5-29 Table 5-17: DWR 7-3R Single Dry Year Supply and Demand Comparison (AF) ................... 5-29 Table 5-18: DWR 7-4R Multiple Dry Years Supply and Demand Comparison (AF) ............... 5-30 Table 5-19: DWR 7-5 Five-Year Drought Risk Assessment (AF) ................................ .......... 5-31
2025 Urban Water Management Plan Public Draft 5-1
5 City of Rialto
This chapter describes information specific to the City of Rialto, its supplies, demands , and water use efficiency programs. The information and analysis in this chapter are supplemental to the regional information presented in Part 1 of the 202 5 RUWMP and are provided to meet the City of Rialto’s reporting requirements for 202 5 under the UWMP Act.
IN THIS S ECTIO N
• System Description
• Water Use
• SBX7 -7 Compliance & Future
Water Use Efficiency
Requirements
• Water Supply
• Water Service Reliability
Assessment
• Drought Risk Assessment
• Water Shortage Contingency
Plan Summary
• Demand Management Measures
• Adoption, Submittal, and
Implementation
City of Rialto
2025 Urban Water Management Plan Public Draft 5-2
5.1 System Description
Three different entities provide water service to different portions of the City of Rialto (City or Rialto): the City through its water system operator Rialto Water Services, LLC and Veolia Water West Operating Services, Inc. (Rialto Water Services/Veolia), the West Valley Water District (WVWD), and the Fontana Union Water Company (FUWC). Rialto’s municipal water system provides potable and recycled water to retail customers primarily within the City and serves approximately one-half of the population of the City. The service area is essentially the incorporated portion of the City located between Interstate 10 and State Route 210. The City's service area is shown in Figure 5-1. Rialto is a retail public water supplier that meets the definition of an urban water supplier with over 12,300 municipal water service connections in 2025.
Rialto sits at the base of the San Bernardino Mountains in the interior valley known as the San Bernardino Valley and within the Santa Ana River Basin Watershed. The topography ranges from 1120 feet to a high of 1520 feet above sea level. Land use within the service area is principally composed of single and multi-family residences, a centralized business and commercial district, and some institutional and industrial areas. The City distributes its water through a 162-mile network of distribution mains with pipelines sizes ranging from 2 to 48 inches. The water system consists of three pressure zones with subzones that provide sufficient water pressure to customers.
This section describes the population and land uses within the City’s service area. The regional climate, which includes Rialto’s service area, is described in Part 1, Chapter 2 of the 2025 RUWMP.
City of Rialto
2025 Urban Water Management Plan Public Draft 5-3
Figure 5-1: City of Rialto Water Service Area Map
City of Rialto
2025 Urban Water Management Plan Public Draft 5-4
5.1.1 Population
Population estimates for the City are based on data from the U.S. Census Bureau and the Southern California Association of Governments (SCAG) (Southern California Association of Governments, 2024). A geographic information systems (GIS) analysis of 2020 Census data was used to determine the City’s 2020 service area population, 56,769 people. The 2020 population and the number of residential connections served by the City in 2020 were used to derive a 2020 persons per connection factor of 4.8. This factor was then multiplied by the City’s number of connections in 2025 to estimate 2025 population served by the City as 59,264 people.
To project the population served by the City from 2030 to 2050, SCAG projected the number of households for 2019, 2035, and 2050. A GIS analysis of SCAG projection data was used to determine the SCAG estimated number of households within the City’s service area. To estimate the number of households in 2020, the SCAG data was linearly interpolated between 2019 and 2035. A 2020 persons per household factor of 3.9 was calculated based on the 2020 Census population. This 2020 persons per household factor was applied to the number of connections projected for the City’s service area. Details pertaining to projected connections are discussed in Section 5.2.2. The projected population for the City is provided in Table 5-1.
Table 5-1: DWR 3-1R Current and Projected Population
POPULATION SERVED 2025 2030 2035 2040 2045 2050
TOTAL: 59,264 67,923 68,802 69,680 70,559 71,437
5.1.2 Land Use
SCAG’s projections are developed based on land uses. Based on the SCAG land use dataset, much of the land use within Rialto's Service Area is residential (approximately 59%). Of the non- residential uses, 12% is designated as specific plan, 11% is industrial, 13% is commercial, and 5% is open space and recreation.
SCAG prepares demographic forecasts based on land use data for their region through an extensive process that emphasizes input from local planners and is done in coordination with local and regional land use authorities, incorporating essential information to reflect anticipated future populations and land uses. SCAG’s projections undergo extensive local review, incorporate zoning information from city and county general plans, and are supported by Environmental Impact Reports.
5.2 Water Use
This section describes the current and projected water uses within Rialto’s service area. Rialto serves potable water for domestic use and recycled water for irrigation. Section 5.2 addresses City of Rialto
2025 Urban Water Management Plan Public Draft 5-5
potable water demand and provides for the reporting of raw water demand delivered for urban use for the year 2025. Recycled water is discussed in Section 5.4.
5.2.1 Water Use by Sector
Rialto categorizes its water customers into three categories for the purposes of billing:
Residential, Commercial, and Government. The numbers of active connections in each category from 2021 to 2025 are shown in Table 5-2. Residential connections include both single family and multifamily connections.
Table 5-2: City of Rialto 2021-2025 Connections by Customer Class CUSTOMER CLASS 2021 2022 2023 2024 2025
Single-Family 10,618 10,488 10,538 10,596 10,800
Multi-Family 446 441 441 447 457
Commercial 799 789 798 804 649
Government 51 50 50 48 45
Landscape 381 376 385 392 385
TOTAL: 12,295 12,144 12,212 12,287 12,336
5.2.1.1 Past Water Use
Rialto’s actual water use by customer class from 2021-2025 is shown in Table 5-3. Rialto’s water consumption by customer class in the last five years is shown in Figure 5-2. Water losses are calculated based on billed consumption compared to actual production data. Approximately 63% of Rialto’s total deliveries were to residential connections, followed by 20% to commercial customers, and the remainder to municipal customers.
City of Rialto
2025 Urban Water Management Plan Public Draft 5-6
Table 5-3: 2021-2025 Actual Water Use (AFY)
CUSTOMER CLASS 2021 2022 2023 2024 2025
Single-Family 4,506 4,593 4,237 4,465 4,501
Multi-Family 1,103 1,125 1,073 1,096 1,071
Commercial 769 784 743 807 1,691
Government 293 298 440 439 338
Hydrant 84 86 37 55 59
Landscape 1,216 1,240 909 1,017 1,281
Water Losses 571 719 524 373 0
TOTAL: 8,542 8,844 7,963 8,252 8,942
Figure 5-2. City of Rialto 2021-2025 Water Consumption by Customer Class
8,542 8,844
7,963 8,252
8,942
0 1,000
2,000
3,000
4,000
5,000
6,000
7,000
8,000
9,000
10,000
2021 2022 2023 2024 2025
Demand, AFY
Single Family Multi-Family Commercial Government
Hydrant Landscape Water Losses Total
City of Rialto
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5.2.1.2 Distribution System Water Losses
Distribution system water losses are the potable water losses from the point of water entry to the distribution system to the point of delivery to the customer’s system. Water loss can result from aging infrastructure, leaks, seepage, theft, metering inaccuracies, data handling errors, and other causes. Addressing water losses can increase water supplies and recover revenue.
The City monitors its water loss and prepares an annual American Water Works Association (AWWA) Water Audit to estimate the volume of water loss. The City has submitted all required water loss audits to the State, as shown in Table 5-4.
Table 5-4: DWR 4-5R Month Water Loss Audit Reporting
Public Water System ID #
Reported in Table 2-1R Reporting Period Submitted to DWR Water Loss Audit Program
CA3610038 2020 Yes
2021 Yes
2022 Yes
2023 Yes
2024 Yes
DWR NOTES:
2020 AWWA: 2020 Water Audit Veolia RWS.xls
2021 AWWA: 2021 Water Audit Veolia RWS 09272022.xls
2022 AWWA: Rialto City of CY2022 Water Loss Audit Validated Updated 231214 (1).xlsx 2023 AWWA: Rialto CY2023 - AWWA Water Audit V6.xlsx
2024 AWWA: City of Rialto CY2024 - Validated Water Audit.xlsx
California Water Code (CWC) Section 10608.34 required the State Water Resources Control Board (SWRCB) to develop water loss performance standards for urban retail water suppliers to minimize water waste through system leaks. Water loss performance standards were developed through a rulemaking that became effective in 2023. Under the regulations, each supplier will be required to comply, by 2028, with an individualized volumetric water loss standard based on real loss, using the economic model developed by the SWRCB and the supplier’s own unique data.
Real loss is the physical loss of water from water distribution systems, as opposed to apparent losses, which are revenue losses due to meter inaccuracies, billing errors or unauthorized consumption. A supplier’s baseline water loss is calculated as the average water loss from at least 3 of the 4 water loss audits from 2017 – 2020. The real water loss performance standard is City of Rialto
2025 Urban Water Management Plan Public Draft 5-8
based on gallons per service connection per day (gpscd), or gallons per mile of pipe per day (gpmd), depending on how the supplier reports real loss. Post-2028 compliance with volumetric water loss standards will be assessed every three years based on the average of the supplier’s real loss from the preceding three years, with an allowed variation of five gpscd above the supplier’s water loss standard. Apparent loss standards are equal to the baseline apparent loss and compliance is evaluated at the same time as compliance with the Real Water Loss Performance Standard.
Although the compliance period has not yet started, CWC Section 10631 (d)(3)(C) requires water suppliers to provide data in the UWMP to show the supplier’s progress toward meeting its SWRCB water loss performance standard.
Based on data released by the State on January 30, 2026, Rialto’s baseline real water loss is
37.9 gpscd and the real water loss standard is 18.4 gpscd, and the apparent loss standard is the baseline of 21.1 gpscd. As shown in Table 5-5, based on the most recent water loss audit from 2024, Rialto has not yet met the real water loss performance standard, but is working toward that goal by 2028. Section 5.1 discusses Rialto’s programs to assess and manage distribution system real loss.
City of Rialto
2025 Urban Water Management Plan Public Draft 5-9
Table 5-5: DWR 4-6R Progress Towards 2028 Water Loss Standard Public System ID #
Reported in Submittal
Table 2-1R
Did the Water
Board Calculate
a Water Loss
Standard for this
Public System?
2028 Real Water
Loss Standard
per Unit per day
Units for Real Water
Loss Standard
Number of
Units
Volume of Total
Real Water Loss
(from AWWA
Water Loss Audit)
2025 or Most
Recent Year Real
Water Loss per
Unit per Day
2028 Apparent
Water Loss
Standard per Unit
per Day
Units for Apparent
Water Loss
Number of
Connections
Volume of Total
Apparent Loss
(from AWWA
Water Loss
Audit)
2025 or Most
Recent Year
Apparent Water
Loss per Unit per
Day
CA3610038 Yes 18.4 gpscd 12,451 433 31.1 21.1 gpscd 12,451 197 14.1 City of Rialto
2025 Urban Water Management Plan Public Draft 5-10
5.2.2 Projected Water Use
As shown in Figure 5-3, water demand has generally remained consistent since 2021, which is most likely due to permanent conservation in response to droughts, state mandated water use reduction targets, more efficient appliances and plumbing, and conservation efforts made by the City and its customers. Historic demand trends and water use per connection for each connection type (single-family residential, multi-family residential, commercial, etc.) were assessed along with expected growth rates to project demand through 2050. The major assumptions used to develop demand projections are described below:
Baseline Water Use: A historic baseline period is used to approximate “normal” demand patterns representative of what is expected in the future given normal conditions for influential factors impacting demand, known as “demand drivers”. A key demand driver is rainfall. Baseline years incorporate impacts of dry and wet years since demand typically fluctuates with rainfall due to the need for more irrigation in dry years and less in wet years. For this UWMP, a baseline period of 2021-2025 is used, which captures three average rainfall years, one wet year (2023), and one dry year (2021). This baseline period captures a wide range of demand drivers to approximate an average or normal demand pattern. A baseline water use per connection was established for each connection type.
Future % Reduction: Based on the State’s indoor water use standard of 42 Gallons per Capita per Day (GPCD), it was assumed that new residential connections would be more efficient and meet this standard once constructed. Additionally, suppliers are required to reduce water demands in alignment with “Making Conservation a California Way of Life Regulation” (CWOL Regulation) over the next 30 years. Therefore, it was assumed that existing residential customers may reduce indoor water demands by 3% by 2030 and 1% by 2035 and onward, while new connections are anticipated to reduce indoor water demands by 25% based on newer efficient technology and alignment with the latest energy efficient plumbing codes. Indoor use demand factors for new single-family connections were assumed to reduce by 25% by 2030 relative to current baseline under the assumption that new connections would meet Urban Water Use Objective Indoor GPCD targets.
Although Rialto also focuses its demand management measures on other categories, such as outdoor water use efficiency, and has specific programs to support businesses, no adjustments were made to future landscape demand factors to be conservative for the purposes of supply planning.
Growth Rate: Projected connection growth for each use type is based on historic connections growth for 2021 to 2024 for each customer class. The total number of projected single family residential connections for 2030 was custom entered based on the City’s known near-term developments. The estimated single-family residential connection count for 2030 is 2,245 new connections and includes estimated unit counts based on the Specific Plan near Foothill, Renaissance Plan, other known residential communities, and an assumption of an additional 650 connections to capture projected demand for accessory dwelling units (ADUs), as recently experienced by the City.
City of Rialto
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Table 5-6. Growth Rates used to Develop Projected Demand CUSTOMER CLASS 2021-2024 Annual Growth
Rate in Connections
Number of New Connections
per 5-Year Period
Single-Family Residential 0.42% 226
Multi-Family 0.22% 5
Commercial 0.26% 8
Institutional/Governmental -2.22% 0
Landscape 0.95% 18
Water Loss: Over the last five years, water losses have ranged from 2% to 20%. Recently, the City’s water losses have remained closer to 6%. To be conservative, the average water loss over the last five years of 8% was applied to the projections through 2050.
Total Projected Demand: For each connection type, the baseline water use per connection was multiplied by the projected future number of connections to estimate future water use by connection type. The water loss percentage was applied to the subtotal of demand for all connection types to determine the total projected future demand. Table 5-7 and Figure 5-3 present projected demands through 2050.
Table 5-7: DWR 4-2R Projected Demands for Water (AF)
CUSTOMER CLASS 2030 2035 2040 2045 2050
Single-Family 5,268 5,324 5,380 5,436 5,492
Multi-Family 1,111 1,115 1,119 1,123 1,128
Commercial 854 865 876 887 897
Institutional/Governmental 334 334 334 334 334
Landscape 1,192 1,246 1,300 1,354 1,408
Losses 701 711 721 731 741
TOTAL: 9,460 9,595 9,730 9,865 10,000
City of Rialto
2025 Urban Water Management Plan Public Draft 5-12
Figure 5-3: City of Rialto Historic and Projected Demand (AFY) Table 5-7 satisfies the requirement to include anticipated water conservation savings when developing future demand projections since they account for historically low water use in 2023.
The significant demand reduction in 2023, which was a wet year, demonstrates that customers modified outdoor water use behaviors based on rainfall, which supports water use efficiency.
Additionally, the baseline period demands on a per connection basis are lower than the long- term average, indicating that customer use patterns are becoming more efficient, and these efficiency gains are embedded in the projected future demands. Therefore, some conservation savings were considered and included in developing demand estimates for the next 25 years.
However, this UWMP projects demand to plan for supply reliability if demands continue in alignment with historic patterns rather than in alignment with new water use efficiency standards, so the demand projections may not reflect all the water use savings needed to meet the Urban Water Use Objective (UWUO) requirements. Rialto is complying with and planning for new water use efficiency standards as described in Section 5.1.
5.2.3 Water Use for Lower Income Households
Senate Bill 1087 requires water use projections in an UWMP to include the projected water use for single-family and multi-family residential housing for lower income households as identified in the housing element of any city, county, or city and county in the service area of the supplier.
Based on SCAG’s 6th cycle final Regional Housing Needs Allocation (RHNA), it is estimated that about 41 percent of all Rialto households qualify as lower income. It should be noted that approximately half of the City of Rialto is within the City’s water service area, while the other half is served by WVWD and FUWC. However, a detailed breakdown of the household income categories within the water service area was not available; therefore, the City-wide estimate of -
2,000
4,000
6,000
8,000
10,000
12,000Water Demand (AFY)
Actual Total Potable Demand (AFY) Projected Demand
City of Rialto
2025 Urban Water Management Plan Public Draft 5-13
41 percent was used. These lower-income water demands have been included in future demand projections.
Table 5-8: DWR 4-3R Inclusion in Water Use Projections
Are Future Water Savings Included in Projections? Yes, Section 5.2.2 Are Lower Income Residential Demands Included in Projections? Yes
5.2.4 Climate Change Considerations
A topic of growing concern for water planners and managers is climate change and the potential impacts it could have on California’s future water supplies.
Recent climate change modeling for the Santa Ana River (SAR) watershed suggests that a changing climate will have multiple effects on the Region. Adaptation and mitigation measures will be necessary to account for these effects. Part 1 Chapter 2 includes an assessment of the potential impacts of climate change.
City of Rialto
2025 Urban Water Management Plan Public Draft 5-14
5.3 SBX7-7 Compliance & Future Water Use Efficiency
Requirements
SBX7-7 was incorporated into the UWMP Act in 2009 and required that all water suppliers increase water use efficiency with the overall goal to decrease per capita water consumption within the state by 20 percent by the year 2020.
SBX7-7 required DWR to develop certain criteria, methods, and standard reporting forms through a public process that water suppliers could use to establish their baseline water use and determine their water conservation targets. SBX7-7 and DWR's Methodologies for Calculating Baseline and Compliance Urban Per Capita Water (State of California Department of Water Resources, 2021) specify methodologies for determining the baseline water demand, 2015 interim urban water use target and the 2020 urban water use target for the City as described in the 2020 UWMP. This section also demonstrates that the City achieved its 2020 water use target.
Table 5-9 below establishes the City’s 2020 actual and 2020 target GPCD. As shown, the City met its 2020 target. Most recently, in 2025, the water use was 135 GPCD, which is well below the 2020 target of 171 GPCD.
Table 5-9: SBX7-7 2020 Target Progress
2020 Target GPCD 2020 Actual GPCD Did Supplier Achieve Target? 171 143 Yes
New water use efficiency standards from the CWOL Regulation supersede SBX7-7 standards.
In 2018, two policy bills were enacted by the California Legislature, Assembly Bill 1668 (AB1668, 2018) and Senate Bill 606 (SB606, 2018), collectively referred to as the “2018 Water Conservation Legislation.” Based on the 2018 Water Conservation Legislation, related legislation, and subsequent adoption of the CWOL Regulation, each urban retail water supplier must comply with its UWUO. DWR and the SWRCB have developed a reporting framework for calculating the UWUO and compliance annually with efficiency standards becoming increasingly stringent through 2040.
The demand projections in this UWMP incorporate portions of the UWUO, such as the indoor residential standard, as described in Section 5.2.2. Rialto will plan and implement necessary demand management measures (described in Section 5.1) to support meeting the UWUO.
Demand Management Measures (DMMs) and UWUO compliance planning enhance resiliency for drought and other water shortage conditions as described in Sections 5.1, 5.7, and 5.8
City of Rialto
2025 Urban Water Management Plan Public Draft 5-15
5.4 Water Supply
The City’s municipal water system generally obtains supplies from the following different types of sources:
• Groundwater from four different adjudicated groundwater basins: the Rialto Basin, Lytle Creek Basin, North Riverside Basin and the Bunker Hill Basin. The City also receives additional Bunker Hill groundwater delivered through a shared delivery system called the Baseline Feeder.
• Surface water from canyon surface flows on the east side of the San Gabriel Mountains, including the North Fork Lytle Creek, Middle Fork Lytle Creek and South Fork Lytle Creek, which are treated at the Oliver P. Roemer Water Filtration Plant (Roemer).
Roemer is owned and operated by WVWD, and the City of Rialto has a 25% share of the original 6 million gallons per day (MGD), 1.5 MGD capacity of the Facility. • Emergency stand-by agreements with the City of San Bernardino and Riverside- Highland Water Company (RHWC).
• Recycled water is available from the City’s Wastewater Treatment Plant.
More information about local surface water and groundwater basins is included in Part 1, Chapter 3 of the 2025 RUWMP.
5.4.1 Purchased or Imported Water
Rialto does not currently purchase imported California State Water Project (SWP) water or other supplies but does purchase SWP water for groundwater recharge and management.
5.4.2 Groundwater
Groundwater currently supplies the majority of Rialto's total supply, and the City will continue to rely on groundwater as its preferred source of supply, augmented with surface supplies when available. The City produces water from four different adjudicated groundwater basins: the Rialto Basin, Lytle Creek Basin, Riverside North Basin and the Bunker Hill Basin. Rialto participates in several ongoing water conservation measures through the Rialto Basin Groundwater Council to optimize and enhance the use and reliability of local groundwater water resources. Relevant portions of the adjudications and judgments that govern groundwater use are discussed in Part 1, Chapter 3 of the 2025 RUWMP.
5.4.2.1 San Bernardino Basin (SBB), which includes Bunker Hill and Lytle Basins The City currently has one well in the Bunker Hill Basin, City Well #4A, and is also supplied Bunker Hill Basin groundwater produced and delivered through the Baseline Feeder. There are no restrictions on Rialto’s extractions from the Bunker Hill Basin except within the area of the Lytle Creek Region and the City of San Bernardino’s groundwater management zone, which restricts new or additional pumping. Restrictions on the City of Rialto’s pumping rights from the Bunker Hill Basin are that all the water is to be used within the boundaries of San Bernardino Valley.
City of Rialto
2025 Urban Water Management Plan Public Draft 5-16
The City owns groundwater extraction rights in the Lytle Creek groundwater basin. The basin was adjudicated under the 1924 Judgment No. 17030 from the Superior Court of San Bernardino County and is based on the City’s stock ownership in the Citizens Land and Water Company, the Lytle Creek Water and Improvement Company, and the companies that the City acquired which were named in the 1924 Judgment (Rialto Domestic Water, Rancheria Water Company and Mutual Water Company). The 1924 Judgment restricts the place of users and rate of extraction for the right to export out of the Lytle Creek Region. The Lytle Creek Region is comprised of the entire Lytle Creek Basin and some portions of the Bunker Hill Basin.
The Lytle Creek Groundwater Basin is highly porous and easily replenished during heavy precipitation years. Recharge for the basin is from storm runoff in the Lytle Creek watershed and from percolation of SWP Water by the San Bernardino Valley Municipal Water District (San Bernardino Valley or SBV). The depth of groundwater in the basin varies from 50 feet to 400 feet depending on whether the area is in a drought or wet cycle. Well production varies in the basin as the basin levels change from year to year. The City’s long term water supply from the basin varies from 1,700 to 5,000 acre-feet per year. There is no known contamination within the Lytle Creek Groundwater Basin, and no contamination is expected in the future.
5.4.2.1.1 Baseline Feeder
In 1991, the City entered into a joint venture agreement with San Bernardino Valley, WVWD and the RHWC to construct the Baseline Feeder. The Baseline feeder is a 48- inch transmission main with a capacity of 60 MGD designed to transport water from the Bunker Hill basin west to the Rialto area. The City owns 33 percent of the pipeline from Meridian Avenue and Baseline Road to Cactus Avenue and Baseline Road. In 1991, the City and WVWD entered into an agreement with SBV to participate in the financing of reaches one and two of the pipeline. In May 2012, the City, WVWD, RHWC and SBV entered into a Restated and Amended Agreement for the Construction, and Operation and Maintenance of the New Baseline Feeder. This allowed for the construction of two new wells located in the Bunker Hill Basin and booster station. The City and WVWD were given the right to have access to 2,500 acre feet per year (AFY) and 5,000 AFY respectively, at an approximate operation and maintenance cost of $130 to $140 per acre foot for 20 years.
In 1991, the City entered into an agreement with WVWD to jointly construct and own a 1.0- million-gallon reservoir and booster station to boost water from the wells in the 9th Street and Lytle Creek Wash areas into the Baseline Feeder. The City has one-third ownership in the reservoir and booster station. The reservoir acts as a stilling well to remove entrapped air from the well discharges. City Well #4A pumps from the Bunker Hill basin directly into the reservoir and is then boosted into the Baseline Feeder for delivery to Rialto.
The City is also able to take delivery through the Baseline Feeder of water from the City of San Bernardino Municipal Water Department (SBMWD), if needed. This water is provided by SBMWD, up to 3,000 gpm, from the Newmark Groundwater Contamination Superfund Site. This water is considered surplus water by SBMWD, and it may be suspended when SBMWD needs the water to meet its own demands.
City of Rialto
2025 Urban Water Management Plan Public Draft 5-17
All water delivered through the Baseline Feeder is Bunker Hill groundwater and is included in the City’s total Bunker Hill production for the purposes of this plan.
5.4.2.2 Rialto-Colton
Rialto has groundwater extraction rights in the Rialto-Colton Basin. The basin was adjudicated under the 1961 Decree No. 81264 of the Superior Court of San Bernardino County and is managed by the Rialto Basin Management Association (stipulated parties of the judgment).
When the basin’s three index wells (WVWD Well No. 11 and 13, and Rialto’s Well 4) highest average mean groundwater level elevations is above 1002.3 feet when measured during March, April, or May, the City has no restrictions on yearly extractions. The City has no restrictions on the rate of pumping per minute or day. When the highest average standing water levels in the three index wells falls below 1002.3 feet msl and is above 969.7 feet msl, the City is restricted to total groundwater extractions of 4,366 AFY. This extraction right is based on the City’s listed rights in the decree, ownership of wells listed in the decree, stock ownership in the Citizens Land and Water Company and stock ownership in the Lytle Creek Water and Improvement Company. The extraction rights listed in the 1961 decree total 15,290 AFY.
When the average of the three index wells drops below 969.7 feet msl, ground water extractions are reduced for all parties stipulated in the decree by one percent per foot below the 969.7-foot level, but not to exceed 50-percent reduction.
Several other entities also withdraw water from the Rialto Basin. FUWC has one well located within the basin but was omitted from the adjudication decree. In 2018, the City, San Bernardino Valley, FUWC, and Cucamonga Valley Water District entered into a Settlement Agreement that resulted in FUWCs No Man’s Land production of 5,014 AFY being counted as part of the Rialto Basin production limits in the 1961 decree. These parties also agreed to form a Rialto Basin Groundwater Council (Rialto Basin GC), which was formed in 2021. The Rialto Basin GC is developing a sustainable groundwater management plan and anticipates implementing groundwater recharge projects to restore groundwater levels and increase reliability.
The City has entered into an agreement with the County of San Bernardino to lease 1,600 AFY of its water rights during drought conditions to allow the San Gabriel Valley Water Company (SGVWC) to extract and remove volatile organic compounds (VOC) from the contaminant plumes. A separate agreement provides Rialto with funding to drill a new well to make up for the lost supply.
Extractions from the Rialto Basin have been limited in recent years due to groundwater contamination plumes of VOC from the Mid Valley Landfill and perchlorate from abandoned rocket fuel plants in the northern parts of the City. A groundwater treatment program is in place to extract and remove VOC’s and perchlorate from the groundwater basin thereby restoring the City’s ability to have access to all of their Rialto Basin rights. It is expected that the City will be able to utilize these rights starting in 2045, once the lease agreement ends.
The City has a total water right allocation in the Rialto Basin of 4,366 AFY, including 1,520 AFY that are fixed rights and 2,846 AFY that are adjustable and subject to a percent reduction each City of Rialto
2025 Urban Water Management Plan Public Draft 5-18
year based on groundwater levels in the index wells. Over the previous 10 years, the average percent reduction has been nearly 38 percent and was 50 percent in 2025. For the purposes of this plan, the City and the other agencies who pump from the Rialto Basin are assuming a 50- percent reduction in adjustable rights in the planning period.
5.4.2.3 Riverside North
The City has one well, Chino 2, that produces from the Riverside North Basin. This basin was discussed further in Part 1 Chapter 3.
The City’s historical production for the past five years is shown in Table 5-10.
Table 5-10: DWR 6-1R Groundwater Pumped Last Five Years (AF)
GROUNDWATER TYPE LOCATION OR
BASIN NAME 2021 2022 2023 2024 2025
Alluvial Basin SBB (Bunker Hill) 2,209 1,734 1,384 1,670 2,311 Alluvial Basin SBB (Bunker Hill via
Baseline Feeder) 1,357 1,405 1,654 1,591 882
Alluvial Basin SBB (Lytle) 1,692 1,273 1,067 1,244 1,563 Alluvial Basin Rialto-Colton 1,984 2,112 3,914 4,259 3,548 Alluvial Basin Riverside North 617 1,532 1,301 804 1,458 TOTAL: 7,859 8,056 9,320 9,568 9,762
5.4.3 Surface Water
The City has a total of 115.63 miner’s inches (1.0 miner’s inch =9.0 gallons per minute) or 1,040.67 gallons per minute (gpm) of surface water diversion rights in Lytle Creek. The surface water diversion rights for Lytle Creek were determined in the 1897 McKinley Decree entered in Los Angeles Superior Court Case No. 20,790. The City owns 21.98% of the shares of the Lytle Creek Water & Improvement Company. The Lytle Creek Water & Improvement Company realized a total of 329.39 miner’s inches from the decree. The City obtained 72.4 miner’s inches from its stock shares in the Lytle Creek Water & Improvement Company. The City also obtained an additional 43.23 miner’s inches of Lytle Creek surface water diversion rights when the City purchased the Rialto Domestic Water Company.
The City utilizes all its surface water diversion rights in Lytle Creek through its ownership of 1.5 MGD of capacity in the Roemer Water Filtration Facility that WVWD owns and operates. The surface water from Lytle Creek is diverted by Southern California Edison at the mouth of Lytle Creek Canyon to generate electrical power at its Fontana Power Plant located on the east side City of Rialto
2025 Urban Water Management Plan Public Draft 5-19
of Riverside Avenue at the intersection of Linden Avenue. WVWD bills the City for its portion of Roemer operation and maintenance costs.
When the flows at the mouth of Lytle Creek Canyon drop below 7,182 gpm (798 miner’s inches), all diversion rights holders must reduce their diversions to a prorated schedule set in the 1897 decree. If the City is not receiving its full Lytle Creek surface water allotment, it is permitted to make up the difference by additional pumping in the Lytle Creek Region, which is part of the SBB.
5.4.4 Stormwater
Rialto is participating in regional project planning efforts to capture additional stormwater for purposes of groundwater recharge to increase sustainability of the basins Rialto produces water from. These regional projects are discussed in Part 1 Chapter 3.
5.4.5 Wastewater and Recycled Water
Rialto, through its operator, Rialto Water Services LLC/Veolia Water West Operating Services, Inc., maintains and operates the City of Rialto wastewater collection system and treatment plant. All the wastewater flows from the City are collected by the City's local sewer mains and delivered to the Rialto Wastewater Treatment Plant. Currently the Rialto Wastewater Treatment Plant also collects, treats, and disposes of the wastewater from the WVWD service area and some areas of the City of Fontana through Extra-Territorial Agreements. Currently the City’s WWTP is permitted for 11.7 MGD of treatment capacity and treats an average of 7 MGD as of 2025. It is estimated that approximately 43% of the wastewater collected at the City of Rialto WWTP was generated within Rialto’s water service area in 2025.
5.4.5.1 Potential, Current, and Projected Recycled Water Uses The Rialto Wastewater Treatment Plant is a Grade V plant with tertiary treatment that discharges its treated wastewater to serve landscape irrigation purposes and to the Santa Ana River. The City maintains a recycled water network using effluent from its wastewater treatment plant. There were no recycled water deliveries in 2025; historical use has been approximately 10 AFY for freeway landscape irrigation, with future expansion planned for park irrigation.
Information about wastewater collected and treated is presented in Table 5-11 and Table 5-12.
Rialto plans to reduce the amount of treated effluent that is discharged from the Rialto Wastewater Treatment Plant into the Rialto Channel, which is a tributary to the Santa Ana River.
The reduction of flow would occur in two parts as infrastructure is constructed, demand for recycled water increases, and certain habitat modifications are implemented within the Rialto Channel. The City would reuse the wastewater by transporting treated wastewater through a pipeline system to recycled water consumers within the service area for direct application.
City of Rialto
2025 Urban Water Management Plan Public Draft 5-20
Table 5-11: DWR 6-2R Wastewater Collected within Service Area in 2025 (AF)
NAME OF
WASTEWATER
COLLECTION
AGENCY
WASTEWATER
VOLUME METERED
OR ESTIMATED
WASTEWATER VOLUME
COLLECTED FROM UWMP
SERVICE AREA IN 2025
NAME OF WASTEWATER
AGENCY RECEIVING
COLLECTED WASTEWATER
WASTEWATER
TREATMENT
PLANT NAME
WASTEWATER
TREATMENT PLANT
LOCATED WITH UWMP
AREA
City of Rialto Estimated 3,332 City of Rialto Rialto WWTP Yes TOTAL: 3,332
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2025 Urban Water Management Plan Public Draft 5-21
Table 5-12: DWR 6-3R Wastewater Treatment and Outcomes within UWMP Service Area in 2025
WASTEWATER
TREATMENT
PLANT NAME &
PLACE ID
NUMBER
DOES THIS
PLANT TREAT
WASTEWATER
GENERATED
OUTSIDE THE
UWMP SERVICE
AREA
2025 VOLUME
OF
WASTEWATER
RECEIVED FROM
UWMP SERVICE
AREA
TOTAL
2025
VOLUME
OF WATER
TREATED
WATER RECYCLED WITHIN
UWMP SERVICE AREA
WATER RECYCLED OUTSIDE
OF UWMP SERVICE AREA
EFFLUENT DISCHARGE
THAT IS NOT A PERMITTED
RECYCLED WATER USE
REQUIRED DISCHARGE FOR
INSTREAM FLOW
DELIVERED TO ANOTHER ENTITY
FOR ADDITIONAL TREATMENT
TREATMENT
LEVEL VOLUME TREATMENT
LEVEL VOLUME TREATMENT
LEVEL VOLUME TREATMENT
LEVEL VOLUME TREATMENT
LEVEL VOLUME
NAME
OF
OTHER
ENTITY
Rialto WWTP Yes 3,332 7,748 0 0 Tertiary 8,0531 Tertiary 5,0672 0 TOTAL: 3,332 7,748 8,053 5,067
Note:
12025 wastewater discharge data greater than influent data; potential meter inaccuracy. 2See Part 1, Section 3.5.2 for details regarding required discharges to the Santa Ana River. Note that this total is included in “Effluent Discharge that is not a Permitted Recycled Water Use” total.
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2025 Urban Water Management Plan Public Draft 5-22
5.4.6 Water Exchanges and Transfers
Rialto does not anticipate regular or long-term transfers or exchanges during the period covered by this Plan. Any transfer or exchanges would be as-needed related to an emergency.
5.4.6.1 Emergency Interties
The City has emergency stand-by agreements with the City of San Bernardino, WVWD and RHWC to meet needs on a short-term basis. The City has mutual aid agreements with the City of San Bernardino, FUWC, RHWC, and WVWD.
5.4.6.2 Future Water Projects
The City completed a Water Master Plan in 2023 to identify necessary upgrades to its water distribution system. The projects identified are intended to increase the reliability of the City’s system; they are not intended to create new sources of supply.
As part of the Rialto Basin GC, the City plans to collaborate with the other parties to implement groundwater recharge in the Rialto Basin to increase water levels. Increased water levels will result in an increase in the City’s allowable pumping from the Rialto Basin, thereby increasing supply. The Rialto Basin is developing a groundwater management plan that will identify recharge goals and projects to increase potential supply.
5.4.7 Summary of Existing and Planned Sources of Water
Rialto's water supply is comprised primarily of local groundwater, supplemented by local surface water when available. The City serves a small amount of recycled water for landscape irrigation.
This same mix of supplies is anticipated to be used in the future. The volume of water utilized from each source in 2025 is summarized in Table 5-13 and projected supply by source is summarized in Table 5-14 and plotted in Figure 5-4.
City of Rialto
2025 Urban Water Management Plan Public Draft 5-23
Table 5-13: DWR 6-8R Actual Water Supplies in 2025 (AF)
WATER SUPPLY ADDITIONAL DETAIL ACTUAL VOLUME WATER QUALITY
TOTAL RIGHT
OR SAFE
WATER YIELD
Groundwater (Not Desalinated) Rialto-Colton 3,548 Potable See Note Groundwater (Not Desalinated) Riverside North 1,458 Potable See Note Groundwater (Not Desalinated) Bunker Hill (part of SBB) 2,311 Potable See Note Groundwater (Not Desalinated) Bunker Hill via Baseline
Feeder 882 Potable See Note
Groundwater (Not Desalinated) Lytle (part of SBB) 1,563 Potable See Note Surface Water (Not
Desalinated) Lytle Creek (part of SBB) 1,101 Potable
TOTAL: 10,863
Note: See Part 1 Chapter 3 for discussion of safe yield of regional groundwater basins.
City of Rialto
2025 Urban Water Management Plan Public Draft 5-24
Table 5-14: DWR 6-9R Projected Water Supplies (AF)
2030 2035 2040 2045 2050
WATER SUPPLY ADDITIONAL DETAIL
REASONABLY
AVAILABLE
VOLUME
REASONABLY
AVAILABLE
VOLUME
REASONABLY
AVAILABLE
VOLUME
REASONABLY
AVAILABLE
VOLUME
REASONABLY
AVAILABLE
VOLUME
Groundwater (Not
Desalinated) Bunker Hill (Part of SBB) 2,017 2,152 2,287 822 957 Groundwater (Not
Desalinated)
Bunker Hill via Baseline
Feeder 2,500 2,500 2,500 2,500 2,500
Groundwater (Not
Desalinated) Lytle (part of SBB) 1,400 1,400 1,400 1,400 1,400 Groundwater (Not
Desalinated) Rialto-Colton 1,343 1,343 1,343 2,943 2,943 Groundwater (Not
Desalinated) Riverside-North 1,200 1,200 1,200 1,200 1,200 Surface Water (Not
Desalinated) Lytle Creek 1,000 1,000 1,000 1,000 1,000
Recycled Water Rialto WWTP 15 15 15 15 15
TOTAL: 9,475 9,610 9,745 9,880 10,015
City of Rialto
2025 Urban Water Management Plan Public Draft 5-25
Figure 5-4: City of Rialto Projected Supply (AFY)
The projected supply and demand during a normal year are shown in Table 5-15.
Table 5-15: DWR 7-2R Normal Year Supply and Demand Comparison (AFY) 2030 2035 2040 2045 2050
Supply Totals
From Table 6-9R
9,475 9,610 9,745 9,880 10,015
Demand Totals
From Table 4-3R
9,475 9,610 9,745 9,880 10,015
DIFFERENCE: 0 0 0 0 0
5.4.8 Energy Intensity
Reporting water energy intensity has many benefits for water utilities and their customers including:
• Identifying energy saving opportunities as energy consumption is often a large portion of the cost of delivering water.
• Calculating energy savings and greenhouse gas (GHGs) emissions reductions associated with water conservation programs.
-
2,000
4,000
6,000
8,000
10,000
12,000
2030 2035 2040 2045 2050
Normal Year Supply Production (AFY)
Recycled Water - Rialto
WWTP
Riverside North
SBB Groundwater - Bunker
Hill
SBB Groundwater - Bunker
Hill via Baseline Feeder
Surface Water - Lytle Creek
SBB Groundwater - Lytle
Rialto-Colton
City of Rialto
2025 Urban Water Management Plan Public Draft 5-26
• Potential opportunities for receiving energy efficiency funding for water conservation programs.
• Informing climate change mitigation strategies.
• Benchmarking of energy use at each water acquisition and delivery step and the ability to compare energy use among similar agencies.
In 2025, Rialto consumed a total of 616 kWh of energy per AF produced.
City of Rialto
2025 Urban Water Management Plan Public Draft 5-27
5.5 Water Service Reliability Assessment
This section considers Rialto’s water supply reliability during normal years, single dry years, and up to five consecutive dry water years. The supply reliability assessment discusses factors that could potentially limit the expected quantity of water available from Rialto’s current sources of supply through 2050.
5.5.1 Constraints on Water Sources
Plumes of various chemical pollutants have been detected in local groundwater basins requiring the installation of well head treatment systems or blending. Rialto’s Perchlorate Contamination Zero Tolerance Policy resulted in taking wells out of service which tested positive for detectible levels of perchlorate. Clean up efforts are through agreement with San Bernardino County and Emhart, responsible parties for the contamination, in coordination with the United States Environmental Protection Agency (EPA) and the Santa Ana Regional Water Quality Control Board and will provide a remedy of the groundwater treatment within the Rialto-Colton Basin.
Based on current conditions and treatment facilities, water quality is not expected to affect Rialto’s supply reliability. However, water quality issues are constantly evolving. Rialto will take action to protect and treat supplies when needed, though water quality treatment is known to have significant costs. These water quality issues are further discussed at a regional level in Part 1 Chapter 3.
Rialto is located in a semi-arid environment. The local groundwater and surface water supplies are influenced by annual precipitation. In extended drought conditions, the surface water supplies in the Lytle Creek region can be severely impacted. In addition, groundwater levels in the Lytle Creek Basin have been known to drop over 300 feet during extended drought periods.
As a result, the City is vulnerable to water shortages due to seasonal hot weather and climatic influences.
The City’s pumping rights in the Rialto Basin are determined by groundwater levels. While the City and the Rialto Basin GC plan to recharge the basin to increase water levels, the City’s pumping rights could be reduced if groundwater levels decline.
The City can shift production to the Bunker Hill basin if needed and will be required to contribute to recharge through regional coordination to maintain reliable supplies in that basin.
5.5.2 Year Type Characterization
In general, groundwater is less vulnerable to seasonal and climatic changes than surface water (i.e. local and imported) supplies. The Western-San Bernardino Watermaster, in collaboration with the Basin Technical Advisory Committee (BTAC), monitor groundwater levels and implement supplemental recharge to maintain long-term sustainability of local groundwater sources. Further discussion of regional water resource management is included in Part 1, Chapter 3.
City of Rialto
2025 Urban Water Management Plan Public Draft 5-28
Per UWMP requirements, Rialto has evaluated reliability for an average year, single dry year, and a five consecutive dry year period. The UWMP Act defines these years as:
• Normal Year: This condition represents the water supplies a supplier considers available during normal conditions. This could be a single year or averaged range of years that most closely represents the average water supply available. • Single Dry Year: The single dry year is recommended to be the year that represents the lowest water supply available.
• Five-Consecutive Year Drought: The driest five-year historical sequence for the Supplier, which may be the lowest average water supply available for five years in a row.
5.5.3 Water Service Reliability
Under single dry and consecutive dry year conditions, the assessment assumes that demands will increase by as much as 5% due to increased outdoor water use. Although water use may decrease in the later years of a multiple year drought due to implementation of conservation measures and drought messaging, the assessment is based on a 5% increase throughout the 5-year drought to be conservative.
As described in Part 1, Chapter 3, the effects of a local drought are not immediately recognized since the region uses the local groundwater basins to simulate a large reservoir for long-term storage. While pumping rights from the Rialto Basin and available surface water may be reduced in dry years, Rialto is able to pump additional groundwater from Bunker Hill, Lytle and Riverside North to meet total demands in dry years and participates in efforts to replenish the basins with imported and local water through regional recharge programs. Rialto’s total groundwater supplies are not reduced in dry years so 2025 is considered the base year for a normal year. Based on the analysis, Rialto does not anticipate any shortage due to single or consecutive dry years. Even though localized drought conditions should not affect supply, Rialto participates in several ongoing water conservation measures and regional recharge projects to optimize and enhance the use and reliability of regional water resources. Rialto also has a water shortage contingency plan to put into action as appropriate to reduce the demand during critical drought years or other supply emergencies.
A summary of the basis of water year data is presented in Table 5-16. The percent of average supply increases in drought years because Rialto’s groundwater production will increase to meet an assumed increase in demands.
City of Rialto
2025 Urban Water Management Plan Public Draft 5-29
Table 5-16: DWR 7-1R Basis of Water Year Data
YEAR TYPE BASE YEAR AVAILABLE SUPPLY IF YEAR TYPE REPEATS
AS PERCENT OF AVERAGE SUPPLY
Average Year 2025 100%
Single Dry Year 2024 105%
Consecutive Dry Year 1st Year 2024 105%
Consecutive Dry Year 2nd Year 2024 105%
Consecutive Dry Year 3rd Year 2024 105%
Consecutive Dry Year 4th Year 2024 105%
Consecutive Dry Year 5th Year 2024 105%
The results of the reliability assessment are summarized in the following tables. The projected supply and demand during a single dry year are shown in Table 5-17. Rialto’s demands in single dry years are assumed to increase by 5% above normal year demands. The local groundwater basins Rialto produces water from have storage for use in dry years so Rialto can produce the volume of water needed to meet 100% of demands in single dry years. Rialto’s supplies are 100% reliable during single dry years.
Table 5-17: DWR 7-3R Single Dry Year Supply and Demand Comparison (AF)
The projected supply and demand during five consecutive dry years are shown in Table 5-18.
Rialto’s demands in multiple dry years are assumed to increase by 5% above normal year demands. The local groundwater basins Rialto produces water from have storage for use in dry years so Rialto can produce the volume of water needed to meet 100% of demands in multiple dry years. Rialto’s supplies are 100% reliable during multiple dry years.
2030 2035 2040 2045 2050
Supply Totals 9,933 10,074 10,216 10,358 10,500 Demand Totals 9,933 10,074 10,216 10,358 10,500 DIFFERENCE: 0 0 0 0 0
City of Rialto
2025 Urban Water Management Plan Public Draft 5-30
Table 5-18: DWR 7-4R Multiple Dry Years Supply and Demand Comparison (AF) 2030 2035 2040 2045 2050
FIRST
YEAR Supply Totals 9,933 10,074 10,216 10,358 10,500 Demand Totals 9,933 10,074 10,216 10,358 10,500 DIFFERENCE: 0 0 0 0 0
SECOND
YEAR Supply Totals 9,961 10,103 10,244 10,387 10,500 Demand Totals 9,961 10,103 10,244 10,387 10,500 DIFFERENCE: 0 0 0 0 0
THIRD
YEAR Supply Totals 9,990 10,131 10,273 10,415 10,500 Demand Totals 9,990 10,131 10,273 10,415 10,500 DIFFERENCE: 0 0 0 0 0
FOURTH
YEAR Supply Totals 10,018 10,159 10,301 10,443 10,500 Demand Totals 10,018 10,159 10,301 10,443 10,500 DIFFERENCE: 0 0 0 0 0
FIFTH
YEAR Supply Totals 10,046 10,188 10,330 10,472 10,500 Demand Totals 10,046 10,188 10,330 10,472 10,500 DIFFERENCE: 0 0 0 0 0
City of Rialto
2025 Urban Water Management Plan Public Draft 5-31
5.6 Drought Risk Assessment
The Drought Risk Assessment (DRA) is required for the 2025 UWMP, with a focus on a five- year consecutive drought scenario beginning in 2026. Because Rialto has access to groundwater basins with significant storage, total available supplies do not vary on a monthly or seasonal basis, so this analysis is conducted on an annual basis. Projected demands and supplies from 2026-2030 are shown in Table 5-19.
Demands for 2026-2030 were assumed to increase at a uniform rate between 2025 actual use and 2030 projected use. 2025 and 2030 values were increased by 5% to reflect higher anticipated demands during dry years, based on the same methodology used when calculating the five-dry consecutive years scenario.
Table 5-19: DWR 7-5 Five-Year Drought Risk Assessment (AF) 2026
Gross Water Use 9,159
Total Supplies 9,159
SURPLUS: 0
2027
Gross Water Use 9,347
Total Supplies 9,347
SURPLUS: 0
2028
Gross Water Use 9,538
Total Supplies 9,538
SURPLUS: 0
2029
Gross Water Use 9,734
Total Supplies 9,734
SURPLUS: 0
2030
Gross Water Use 9,933
Total Supplies 9,933
SURPLUS: 0
City of Rialto
2025 Urban Water Management Plan Public Draft 5-32
5.7 Water Shortage Contingency Plan
The Water Shortage Contingency Plan (WSCP) is a strategic plan that Rialto uses to prepare for and respond to foreseeable and unforeseeable water shortages. A water shortage occurs when water supply available is insufficient to meet the normally expected customer water use at a given point in time. A shortage may occur due to a number of reasons, such as water supply quality changes, climate change, drought, regional power outage, and catastrophic events (e.g., earthquake). Additionally, the State may declare a statewide drought emergency and mandate that water suppliers reduce demands, as occurred in 2014. The WSCP serves as the operating manual that Rialto will use to prevent catastrophic service disruptions through proactive, rather than reactive, mitigation of water shortages. The WSCP provides a process for an annual water supply and demand assessment and structured steps designed to respond to actual conditions.
The level of detailed planning and preparation provide accountability and predictability and will help Rialto maintain reliable supplies and reduce the impacts of any supply shortages and/or interruptions.
The WSCP was prepared in conjunction with the 2025 RUWMP and is a standalone document that can be modified as needed. Rialto’s WSCP is attached as Part 4 Appendix E.
City of Rialto
2025 Urban Water Management Plan Public Draft 5-33
5.8 Demand Management Measures
The Demand Management Measures section outlines the water conservation framework Rialto has utilized over the past five years, is currently implementing, and plans to implement to reduce demand. By successfully achieving its SBX7-7 targets in 2020 and 2025, the City has demonstrated the effectiveness of its conservation strategy. Moving forward, these measures will serve as the foundation for meeting new urban water use objectives and ensuring long-term supply reliability.
5.8.1 Existing Demand Management Measures
Consistent with CWC requirements, the following details the specific DMMs within the service area. These programs represent the City’s ongoing commitment to water-use efficiency and are designed to maintain consumption levels below established benchmarks. Rialto intends to continue programs for the foreseeable future to provide stable, sustainable water management for all customers.
5.8.1.1 Water Waste Prevention Ordinances
The City Ordinance Number 1560 Chapter 12.20: Water Conservation Requirements included in Appendix E outlines efficient water use measures and four stages of increasingly restrictive prohibition with related penalties for non-compliance. The goal of this ordinance is to outline restrictions put in place to help the City reduce water waste.
5.8.1.2 Metering
All existing and new water services are metered throughout the Rialto water service area. A water meter calibration and replacement program is in place to continually improve accurate meter readouts. New services, with the exception of single-family residences and apartment complexes up to and including four units per meter, are required to install a separate water meter for the on-site landscaping. Rialto is installing advanced metering infrastructure (AMI) on all service connections, and the update is scheduled to be completed by December 2026.
5.8.1.3 Conservation Pricing
The conservation tiered rate structure used by Rialto, where efficient water use is billed at a low price and higher water use billed at progressively higher prices, provides the economic incentives to customers to use water efficiently. The tiered rate structure includes three tiers.
The first tier is the volume estimated to be the typical indoor use, the second as the typical outdoor use, and the highest tier as “excessive” use.
5.8.1.4 Public Education and Outreach
At the local level, Rialto provides outreach communication and information regarding conservation efforts, rebates and incentives to its customers through water bill inserts, direct mailers, newsletters, door hangers, direct phone calls, emails, websites, social media, business partnerships, quarterly Rialto Progress Magazine, community forums, educational programs, City of Rialto
2025 Urban Water Management Plan Public Draft 5-34
and information booths at fairs, public events, and water walk events. The customer's monthly bill includes a consumption usage chart that compares to prior years in an easy-to-understand format, informing customers of progress towards conservation targets.
5.8.1.5 Programs to Assess and Manage Distribution System Real Losses Rialto has an active Visible Leak Detection Program to decrease leak response times and minimize water loss throughout the water distribution system. Leaks are generally repaired within two days of discovery. Three field meter readers and two production operator employees staff the program five days per week. Meter readers are required to inspect elements in the water distribution system as they travel respective routes throughout the city. This includes meter boxes, fire hydrants, air-vacuum units, above ground piping and appurtenances. They also look for signs of leaks in soil and paved areas on the routes. Two production operators also check wells, tanks, booster pumps, and appurtenant equipment for leaks each day of the business week. The leak detection activity is conducted as part of routine duties assigned and embedded in the operation’s routine activities. Additionally, Rialto prepares the AWWA Water Loss Audit annually to determine what actions to take to reduce real water loss.
5.8.1.6 Water Conservation Program Coordination and Staffing Support The Water Conservation Program, an active program to encourage efficient use of Rialto's Water Resources, is a coordinated effort throughout Rialto's services area. One staff person coordinates conservation programs, including outreach and education programs. This staff person also oversees the rebates, incentive programs, customer services assistance to administer collections of water waste reports and enforcement of non-compliance by water customers to the current water conservation stage coordination with new development, conditions and enforce the use of water efficient measures. Additionally, Rialto has been a member of the California Water Efficiency Partnership (CalWEP) since 2009, which provides City staff with conservation expertise and technical resources to strengthen its conservation programs.
5.8.1.7 Other Demand Management Measures
Rebates, incentives and giveaways are offered to all water customers promoting efficient use of Rialto's Water Resources. Current rebates include:
• High efficiency spray nozzles - $4 each.
• High efficiency toilets - $50 each (2 per household). • High efficiency washing machines - $100 each.
• Weather-based smart irrigation controllers - $100 each. • Turf replacement - $1 per square foot ($1,000 maximum).
These financial incentives are available to help customers offset the cost of upgrading to water- efficient technologies and reduce overall system demand.
City of Rialto
2025 Urban Water Management Plan Public Draft 5-35
5.9 Adoption, Submittal and Implementation
This section describes Rialto’s process for adopting, submitting, and implementing the 2025 RUWMP and Rialto’s WSCP.
5.9.1 Notice of Public Hearing
A joint notice was provided on behalf of all agencies whose 2025 UWMPs are part of the 2025 RUWMP to all cities and counties and other stakeholders within the region that the 2025 RUWMP is being prepared. This notice was sent at least 60 days prior to Rialto’s public hearing.
The recipients are identified in Part 1 Chapter 1 and include all cities and counties within Rialto’s service area. A second notice was provided to these cities and counties with the date and time of the public hearing and the location where the draft report was available for review.
Rialto provided notice to the public through its website and published announcements of the public hearing in a newspaper on two occasions before the hearing. Copies of the proof of publication are included in Part 4 Appendix E.
5.9.2 Public Hearing and Adoption
Rialto held a public hearing on May 26, 2026, to hear public comment and consider adopting this 2025 RUWMP and Rialto’s WSCP.
As part of the public hearing, Rialto provided information on its baseline values, water use targets, and implementation plan required in the Water Conservation Act of 2009. The public hearing on the 2025 RUWMP took place before the adoption of the Plan, which allowed Rialto the opportunity to modify the 2025 RUWMP in response to any public input before adoption.
After the hearing, the Plan was adopted as prepared or as modified after the hearing.
Rialto’s adoption resolution for the 2025 RUWMP and Rialto’s WSCP is included in Part 4 Appendix E.
5.9.3 Plan Submittal
Rialto will submit the 2025 RUWMP and Rialto’s WSCP to DWR, the State Library, and cities and counties within 30 days after adoption. The 2025 RUWMP submittal to DWR will be done electronically through WUEdata, an online submittal tool.
5.9.4 Public Availability
No later than 30 days after filing a copy of its Plan with DWR, Rialto will make the plan available for public review during normal business hours by placing a copy of the 2025 RUWMP and Rialto’s WSCP at the front desk of the City’s office, and by posting the plans on the City’s website for public viewing.
City of Rialto
2025 Urban Water Management Plan Public Draft 5-36
5.9.5 Amending an Adopted UWMP or Water Shortage Contingency Plan
If the adopted 2025 RUWMP or Rialto’s WSCP is amended, each of the steps for notification, public hearing, adoption, and submittal will also be followed for the amended plan.