May 2026
Draft
Attachment 1
CITY OF MOUNTAIN VIEW 2025 URBAN WATER MANAGEMENT PLAN
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CHAPTER 1: INTRODUCTION
The Urban Water Management Plan (UWMP) provides an analysis of the City of Mountain View’s available water supply, during normal and dry-year scenarios, compared to current and projected water demand. The UWMP is a link between land use planning and water supply planning, developed to evaluate if sufficient water is available to meet the needs of Mountain View’s existing and future water customers. This UWMP update also includes an update to the Water Shortage Contingency Plan. In preparing this UWMP update, staff worked collaboratively with the City’s wholesale water suppliers to exchange necessary information. Notice of the preparation and adoption process was posted in local newspapers and emailed to neighborhood and business liaisons, local water agencies, and the County of Santa Clara. Pursuant to State law, water agencies must update their UWMP every five years.
CHAPTER 2: SERVICE AREA
Mountain View’s municipal water system serves the majority of businesses and residents within the City limits.
A small number of customers are served by the California Water Service Company. The City currently serves 84,413 residents. Future water demand projections were developed based on a snapshot of approved development and the General Plan growth estimates, including the current Housing Element. Collective growth is estimated to reach 148,200 residents within the municipal water service area by 2050, which is a 76% increase from the current level.
CHAPTER 3: WATER SYSTEM OVERVIEW
The City’s municipal water system services three pressure zones and consists of three wholesale water turnouts, four reservoirs, three pump stations, four active groundwater supply wells, and buried pipelines of varying composition, ages, and sizes. Mountain View currently serves 18,009 potable water service connections (18,952 with fire services) and 59 active recycled water service connections. Single-family and multi-family homes account for 86 percent of all connections, with the remaining connections serving commercial, institutional, and industrial accounts and landscape customers.
CHAPTER 4: WATER DEMAND
Mountain View’s historical water demand is shown in Figure ES-1. This figure shows a general downward trend in water use since the mid-1980s, punctuated by rapid drops in water use coinciding with periods of drought, as customers responded to conservation requests.
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Figure ES-1: Historical Water Demand
Mountain View’s water demand projections were developed based on regional modeling efforts completed between 2024 and 2025. Mountain View’s water demand model was most recently revised to account for updated population and employment projections and the impacts of climate change (among other things).
The City’s water demand model includes three scenarios to evaluate and forecast Mountain View’s water demand through the year 2050. The “base-case” scenario represents a high-end estimate of possible future demand. Two additional scenarios were developed to capture water savings expected from passive conservation (e.g., plumbing code efficiencies) and active water conservation measures. Mountain View’s model results are shown in Table ES-1 in five-year increments through the year 2050. For the purpose of this UWMP, the scenario incorporating passive and active conservation savings (Scenario C), is selected for the City’s official demand projections.
Table ES-1: Water Model Results
Water Model Scenario Projected Water Demand (AFY)
2030 2035 2040 2045 2050
Scenario A (Base-Case) 11,160 12,103 12,732 13,316 13,955 Scenario B (Plumbing Codes) 10,876 11,587 12,120 12,630 13,212 Scenario C (Plumbing Codes and Conservation) 10,831 11,512 12,038 12,541 13,116
CITY OF MOUNTAIN VIEW 2025 URBAN WATER MANAGEMENT PLAN
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CHAPTER 5: WATER SUPPLY SOURCES
The City of Mountain View receives the majority of drinking water from the City and County of San Francisco’s Regional Water System (Regional System), operated by the San Francisco Public Utilities Commission (SFPUC). Mountain View is a member of the Bay Area Water Supply and Conservation Agency (BAWSCA), which represents the 26 water agencies that purchase water wholesale from SFPUC. Mountain View also purchases water wholesale from the Santa Clara Valley Water District (now known as Valley Water) and pumps local groundwater from City-owned wells. Mountain View has a recycled water distribution system to meet a portion of the nonpotable demand in the North Bayshore Area. In 2025, the City’s water supply production was 84 percent SFPUC, 8 percent Valley Water, 2 percent groundwater, and 6 percent recycled water. Below is a summary of the City’s water supplies:
• San Francisco: The Regional System draws an average of 85 percent of its supply from the Tuolumne River, collected in Hetch Hetchy Reservoir in Yosemite National Park. This water feeds into an aqueduct system delivering water 167 miles by gravity to Bay Area reservoirs and customers. The remaining 15 percent of SFPUC’s supply is drawn from local surface waters in Alameda County and Peninsula watersheds through the San Antonio, Calaveras, Crystal Springs, Pilarcitos, and San Andreas reservoirs.
• Valley Water: Valley Water is an independent special district that provides wholesale water supply, groundwater management, flood protection, and stream stewardship on behalf of Santa Clara County’s nearly 2 million residents. Valley Water’s service area includes all of Santa Clara County.
Sources of supply for Valley Water include local surface water, imported water from the State Water Project and Central Valley Project, groundwater, and recycled and purified water. Valley Water supplies are used to recharge local groundwater basins, released to local creeks to meet environmental needs, and delivered directly to retail water suppliers through Valley Water’s treatment plants and distribution system.
• Local Groundwater: Mountain View owns and operates water supply wells that extract local groundwater for use as drinking water. City wells pump groundwater from the Santa Clara Basin, which is managed by Valley Water. Approximately two-thirds of all groundwater used in Santa Clara County is recharged by Valley Water from local and imported surface water. • Recycled Water: Mountain View uses recycled water from the Palo Alto Regional Water Quality Control Plant for irrigation, toilet flushing, and industrial uses in the North Bayshore Area. The City has utilized recycled water since 1980. There are currently 59 active customer connections to the City’s recycled water system, including the Shoreline golf course, Shoreline Regional Park, Shoreline Amphitheatre, Charleston Park, and various business and roadway landscaping. A small number of customers also use recycled water for indoor purposes, such as toilet flushing and air cooling.
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Mountain View's historical water supply production is shown in Figure ES-2. A general downward trend is evident over the past 50 years, due mostly to changes in customer base, increased plumbing efficiencies, changes in landscape aesthetics, and periodic drought.
Figure ES-2: Historical Water Supply Production
Projected Water Supply Production
Mountain View maintains a diverse water supply portfolio to meet existing and future needs. Production of each water supply changes based on several factors, including demand, water quality, and drought. In order to meet projected demand, Mountain View expects to utilize the City’s supplies in the approximate volumes presented in Table ES-2. Actual use of each supply will depend on demand, supply conditions, and operational needs.
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Table ES-2: Projected Water Supply Production
Supply Source Projected Water Supply Production (AFY)
2030 2035 2040 2045 2050
SFPUC 8,811 9,092 9,618 10,121 10,696
Valley Water 920 920 920 920 920
Groundwater 200 200 200 200 200
Potable 9,931 10,212 10,738 11,241 11,816
Recycled 900 1,300 1,300 1,300 1,300
Total Supply 10,831 11,512 12,038 12,541 13,116
CHAPTER 6: WATER SUPPLY RELIABILITY
As part of this UWMP update, the City and the City’s wholesale water suppliers have evaluated their ability to meet projected demand during normal and dry years.
Reliability of the SFPUC Regional System
The Regional System provides a safe, reliable water supply for over 2 million residents and various other users in the Bay Area. Key reliability constraints assessed by SFPUC include the effects of climate change and regulatory actions, such as the Bay-Delta Plan Amendment. SFPUC is developing strategies to address these vulnerabilities.
• Bay-Delta Plan Amendment: The State Water Board’s Bay-Delta Plan Amendment establish water quality objectives to maintain the health of the Bay Delta ecosystem. A main goal of the amendment is to increase salmon populations in the Bay Delta and three San Joaquin River tributaries. One of the affected tributaries is the Tuolumne River, which is SFPUC’s primary water source. If the Bay-Delta Plan Amendment is implemented as adopted, SFPUC will be able to meet system demand in normal years, but would experience supply shortages during dry years, up to 43 percent system-wide in some years. The State Water Board, SFPUC, and others are currently negotiating alternative agreements and, at this time, the final resolution of this process is uncertain. • Water System Improvement Plan: To enhance the ability of the Regional System and meet its goals for water quality, seismic reliability, delivery reliability, and water supply, SFPUC approved a $4.8 billion Water System Improvement Plan (WSIP) in 2008. The WSIP included over 30 capital projects related to rehabilitation, construction, replacement, and upgrades to pipelines, reservoirs, CITY OF MOUNTAIN VIEW 2025 URBAN WATER MANAGEMENT PLAN
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dams, treatment facilities, tunnels, and power facilities. The WSIP authorized SFPUC to undertake a number of water supply projects to meet dry-year demands with no greater than 20 percent rationing. • Alternative Water Supply Planning: SFPUC is evaluating new water supplies and other projects that would improve water resilience. Development of additional water supplies and partnerships could reduce SFPUC’s projected supply shortfalls. Projects under consideration include potable reuse, groundwater banking, dry year transfers and other collaborations.
Reliability of Valley Water Managed Supplies
Based on Valley Water’s existing and planned sources of supply, Valley Water expects to be able to meet Countywide demands through 2050 under normal conditions, with rationing limited to 9 percent during extended drought periods.
• Imported Water Constraints: Valley Water’s imported supplies are subject to a number of constraints, including hydrologic variability, regulatory requirements to protect fish and water quality in the Bay-Delta, and conveyance limitations. Imported Bay-Delta supplies are at risk from levee failures due to seismic threats and flooding, sea-level rise and climate change, declining populations of protected fish species, and water quality variations. Local and out-of-County storage can help mitigate the impacts of hydrologic variability. Water quality variations are addressed by blending sources and/or switching sources to Valley Water’s drinking water treatment plants. Algae and disinfection byproduct precursors have been especially challenging during recent droughts. To address some of these constraints, Valley Water continues to evaluate the costs and benefits of participating in the Delta Conveyance Project in addition to other water supply options, including developing additional local supplies, securing and optimizing Valley Water’s existing water system, and expanding water conservation.
• Local Surface Water Constraints: Valley Water’s local surface water is vulnerable to hydrologic variability and operational needs. Reservoirs are sized for annual operation and have multiple management considerations. For example, in wet years, Valley Water’s ability to capture local surface water is limited by Valley Water’s need to provide flood protection. Dam safety requirements have reduced reservoir storage capacities, which Valley Water is working to address. • Groundwater Constraints: Groundwater supply is largely constrained by hydrologic variability and the operational storage capacity within the subbasins. Inflows to the groundwater subbasins are controlled by Valley Water’s managed aquifer recharge program and natural recharge.
CITY OF MOUNTAIN VIEW 2025 URBAN WATER MANAGEMENT PLAN
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Water Service Reliability Assessment
Mountain View plans to meet projected water demand during normal and dry-year scenarios using a combination of existing supplies and demand-reduction measures. Local groundwater and recycled water supplies are projected to be fully available during all year types (normal and dry) through 2050. Valley Water supplies are projected to experience shortfalls up to 9 percent during the latter years of some multiple dry year sequences. Based on the information provided by the SFPUC under their Bay-Delta Plan Amendment scenario, Mountain View will have full SFPUC supply availability during normal years but will experience SFPUC supply shortfalls of up to 48 percent during some dry years (due to a 43% systemwide reduction).
Water Supply and Demand Assessment
Mountain View uses the information on reliability provided by the City’s wholesale suppliers to evaluate the cumulative supply impacts to the City during normal and dry years. Based on the information provided by Valley Water and SFPUC, Mountain View expects to meet current and future water needs during normal years. During dry years, the City intends to utilize existing groundwater wells to limit rationing to 20 percent.
In these instances, the City would also implement demand-reduction strategies from the City’s Water Shortage Contingency Plan to achieve 20 percent drought reductions.
CHAPTER 7: WATER CONSERVATION
Mountain View implements several water conservation measures, in partnership with Valley Water and BAWSCA. Key measures are summarized below:
• Regulations: The City has adopted a Water Waste Prevention Ordinance, Water Conservation in Landscaping Regulations, and the Mountain View Green Building Code.
• Metering: Mountain View has metered customer water use since at least 1938. Current metering efforts include conversion to advanced metering (also known as “smart” metering) and requiring that irrigation be metered separate from other uses.
• Water Loss Control: The City tracks system water loss on an annual basis as part of the City’s water loss control and prevention program.
• Customer Programs: Several programs are available to help customers use water more efficiently.
Examples include: home water reports, Water-Wise House Calls, irrigation budget reports, landscape CITY OF MOUNTAIN VIEW 2025 URBAN WATER MANAGEMENT PLAN
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audits, plumbing fixture replacement (toilets, clothes washers, commercial equipment, and submeters), and landscape upgrades.
• Education and Outreach: Outreach is promoted through school assemblies, landscape education classes, website and social media postings, utility bill design and messaging, bill inserts, brochure racks, a dedicated phone hotline, and booths for public events.
CHAPTER 8: WATER SHORTAGE CONTINGENCY PLAN
Mountain View’s Water Shortage Contingency Plan serves as a flexible framework of planned response measures to mitigate water supply shortages. The Plan describes demand-reduction strategies to meet various stages of shortages, including up to 10 percent, 11 percent to 25 percent, 26 percent to 40 percent, and greater than 40 percent. Each stage includes a set of demand reduction actions that become progressively more stringent as the shortage condition escalates. All of the stages are designed to provide adequate water to protect public health and safety and satisfy the City’s fire protection needs. The City’s Water System Emergency Response Plan and a Risk and Resilience Assessment evaluate impacts from natural disasters and man-made threats on Mountain View’s water supply. SFPUC and Valley Water similarly have prepared studies to evaluate and plan for emergency supply interruptions.
SUMMARY
Mountain View updates the City’s UWMP every five years to evaluate the City’s ability to meet the City’s water needs over the next 25 years. This UWMP considers water demand associated with current customers as well as new customers, arising from implementation of the General Plan and affiliated adopted land use plans and policies. This growth is expected to increase water use by 32 percent between 2025 and 2050.
Mountain View will meet these water needs through continued implementation of water conservation measures and use of the City’s four water supplies: SFPUC, Valley Water, groundwater, and recycled water.
Although actions by the State Water Board may reduce SFPUC’s dry-year supply availability by up to 43 percent system-wide, the final impacts are uncertain at this time and negotiations are ongoing. In the meantime, several options are being studied by SFPUC to meet its contractual obligations and service level goals, and Mountain View’s groundwater wells remain available for use, mitigating impacts from a possible temporary reduction in imported water supply. Mountain View continues to collaborate with SFPUC, Valley Water, BAWSCA, and others to sustainably manage our water supplies and meet the City’s water needs now and in the future.