DRAFT - May 2026
2025 Urban Water Management Plan
DRAFT
Attachment 1
May 15, 2026
City of Sunnyvale
2025 Urban Water
Management Plan
DRAFT
Prepared by HydroScience Engineers, Inc.
DRAFT
Attachment 1
City of Sunnyvale
2025 Urban Water Management Plan
Table of Contents
Page I
www.hydroscience.com
TABLE OF CONTENTS
– Introduction and Overview ................................ ................................ .......... 1-1
1.1 Lay Description ................................ ................................ ................................ ........... 1-2 – Plan Preparation ................................ ................................ ........................... 2-1
2.1 Plan Organization ................................ ................................ ................................ ....... 2-1
2.2 Inclusion of All 2025 Data ................................ ................................ ........................... 2-1
2.3 Coordination ................................ ................................ ................................ ............... 2-2 – System Description ................................ ................................ ...................... 3-1
3.1 History ................................ ................................ ................................ ........................ 3-1
3.2 Organization Structure ................................ ................................ ................................ 3-2
3.3 Climate ................................ ................................ ................................ ....................... 3-2
3.3.1 Climate Change Impacts ................................ ................................ .................... 3-3
3.4 Service Area Population ................................ ................................ ............................. 3-3
3.5 Demographics ................................ ................................ ................................ ............ 3-4
3.5.1 Low-Income Housing ................................ ................................ ......................... 3-4
3.6 Land Uses within Service Area ................................ ................................ ................... 3-5
3.7 Water Supply Sources ................................ ................................ ................................ 3-5
3.8 Distribution System ................................ ................................ ................................ .... 3-5 – Water Use Characterization ................................ ................................ ......... 4-1
4.1 Water Use Objectives ................................ ................................ ................................ . 4-1
4.2 Non-Potable Versus Potable Water Use ................................ ................................ ..... 4-1
4.3 Past, Current, and Projected Water Use by Sector ................................ ..................... 4-1
4.3.1 Historical Water Use ................................ ................................ .......................... 4-2
4.3.2 Distribution System Water Loss ................................ ................................ ......... 4-3
4.3.3 Current Water Use ................................ ................................ ............................. 4-5
4.3.4 Projected Water Use ................................ ................................ .......................... 4-6
4.4 Future Water Savings ................................ ................................ ................................ . 4-7
4.5 Low-Income Housing Water Use Projection ................................ ............................... 4-8
4.6 Climate Change Considerations ................................ ................................ ................. 4-8 – Baselines and Targets ................................ ................................ ................. 5-1 – Water Supply Characterization ................................ ................................ .... 6-1
6.1 Purchased Water ................................ ................................ ................................ ........ 6-1
6.1.1 SFPUC – Wholesaler (Surface Water) ................................ ............................... 6-1
6.1.2 Valley Water – Wholesaler (Surface Water) ................................ ....................... 6-2
6.2 Groundwater ................................ ................................ ................................ .............. 6-3
6.2.1 Basin Description ................................ ................................ ............................... 6-3
6.2.2 Historical Groundwater Pumping ................................ ................................ ....... 6-5
6.3 Stormwater ................................ ................................ ................................ ................. 6-6
6.4 Wastewater and Recycled Water................................ ................................ ................ 6-6 DRAFT
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2025 Urban Water Management Plan
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6.4.1 Wastewater Collection, Treatment, and Disposal ................................ ............... 6-7
6.4.2 Future Wastewater Improvement Projects ................................ ......................... 6-7
6.4.3 Recycled Water System Description ................................ ................................ .. 6-9
6.4.4 Potential, Current, and Projected Recycled Water Use ................................ ...... 6-9
6.4.5 Projected Future Uses of Recycled Water ................................ ....................... 6-11
6.4.6 Recycled Water Optimization and Incentives ................................ ................... 6-13
6.4.7 Recycled Water Streamflow Augmentation and Groundwater Recharge ......... 6-14
6.4.8 Recycled Water Coordination ................................ ................................ .......... 6-14
6.5 Desalinated Water ................................ ................................ ................................ .... 6-14
6.6 Water Exchanges and Transfers ................................ ................................ .............. 6-15
6.7 Future Water Projects ................................ ................................ ............................... 6-15
6.8 Summary of Existing and Planned Sources of Water................................ ................ 6-16
6.9 Energy Intensity ................................ ................................ ................................ ........ 6-17
6.10 Climate Change Impacts to Supply ................................ ................................ ........... 6-18 – Water Supply Reliability and Drought Risk Assessment ........................... 7-1
7.1 Constraints on Water Sources ................................ ................................ .................... 7-1
7.1.1 Water Quality Impacts on Reliability ................................ ................................ ... 7-1
7.1.2 Impacts of Climate Change ................................ ................................ ................ 7-3
7.1.3 Additional Supply Constraints ................................ ................................ ............ 7-6
7.2 Regional Supply Reliability ................................ ................................ ......................... 7-8
7.2.1 SFPUC ................................ ................................ ................................ .............. 7-8
7.2.2 Valley Water ................................ ................................ ................................ .... 7-14
7.2.3 Groundwater ................................ ................................ ................................ .... 7-15
7.3 Water Service Reliability Assessment ................................ ................................ ...... 7-15
7.3.1 Year Type Characterization ................................ ................................ ............. 7-15
7.3.2 Supply and Demand Comparison ................................ ................................ .... 7-17
7.4 Drought Risk Assessment ................................ ................................ ........................ 7-20
7.4.1 Data, Methods, and Basis for Water Shortage Condition ................................ . 7-21
7.4.2 Water Source Reliability ................................ ................................ ................... 7-22
7.4.3 Total Water Supply and Use Comparison ................................ ........................ 7-25 – Water Shortage Contingency Planning ................................ ....................... 8-1
8.1 Water Supply Reliability Analysis................................ ................................ ................ 8-1
8.1.1 Demand Projections ................................ ................................ .......................... 8-2
8.1.2 Supply Projections ................................ ................................ ............................. 8-3
8.1.3 Water Supply Reliability Assessment ................................ ................................ . 8-6
8.1.4 Drought Risk Assessment ................................ ................................ .................. 8-9
8.2 Annual Water Supply and Demand Assessment Procedures ................................ ... 8-10
8.2.1 Decision-Making Process ................................ ................................ ................ 8-10
8.2.2 Data and Methodology ................................ ................................ ..................... 8-11
8.3 Standard Water Shortage Stages ................................ ................................ ............. 8-12
8.3.1 SFPUC Water Shortage Allocation Plan ................................ .......................... 8-13
8.3.2 Valley Water’s Water Shortage Contingency Plan ................................ ........... 8-14
8.3.3 Sunnyvale’s Shortage Stages of Action ................................ ........................... 8-16 DRAFT
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8.4 Shortage Response Actions ................................ ................................ ..................... 8-17
8.5 Consumption Reduction Methods ................................ ................................ ............. 8-21
8.5.1 Public Outreach/Rebates ................................ ................................ ................. 8-21
8.5.2 Water Rate Structure for Conservation ................................ ............................ 8-21
8.5.3 Enforcement Approach ................................ ................................ .................... 8-22
8.6 Water Use Monitoring Procedure................................ ................................ .............. 8-22
8.6.1 Determining Water Shortage Reductions ................................ ......................... 8-23
8.7 Analysis of Revenue Impacts of Reduced Sales during Shortages ........................... 8-23
8.8 Emergency Response Plan ................................ ................................ ...................... 8-23
8.8.1 Sunnyvale Emergency Response Plan ................................ ............................ 8-23
8.8.2 SFPUC Emergency Preparedness Plan ................................ .......................... 8-25
8.8.3 Valley Water Catastrophic Interruption Planning ................................ .............. 8-27
8.9 Seismic Risk Assessment and Mitigation Plan................................ .......................... 8-30
8.9.1 Sunnyvale Seismic Risk Assessment and Mitigation Plans .............................. 8-30
8.9.2 SFPUC Seismic Risk Assessment and Mitigation Plan ................................ .... 8-30
8.9.3 Valley Water Local Hazard Mitigation Plan ................................ ...................... 8-32
8.10 Legal Authority ................................ ................................ ................................ ......... 8-32
8.11 Plan Adoption, Submittal, and Availability ................................ ................................ . 8-32
8.11.1 60-Day Notification ................................ ................................ .......................... 8-33
8.11.2 Notice to Cities and Counties ................................ ................................ ........... 8-33
8.11.3 Public Hearing and Adoption................................ ................................ ............ 8-34
8.11.4 Plan Submittal ................................ ................................ ................................ . 8-34
8.11.5 Public Availability ................................ ................................ ............................. 8-34
8.11.6 Amending an Adopted WSCP ................................ ................................ .......... 8-34 – Demand Management Measures ................................ ................................ . 9-1
9.1 Demand Management Measures for Wholesale Agencies ................................ ......... 9-2
9.2 Demand Management Measures for Retail Agencies ................................ ................. 9-2
9.2.1 Water Waste Prevention Ordinances ................................ ................................ . 9-2
9.2.2 Metering ................................ ................................ ................................ ............ 9-3
9.2.3 Conservation Pricing ................................ ................................ .......................... 9-3
9.2.4 Public Education and Outreach ................................ ................................ .......... 9-4
9.2.5 Programs to Assess and Manage Distribution System Real Loss ...................... 9-7
9.2.6 Water Conservation Program Coordination and Staffing Support ...................... 9-8
9.2.7 Other Demand Management Measures ................................ ............................. 9-8
9.3 Reporting Implementation ................................ ................................ ........................ 9-14
9.3.1 Planned DMM Implementation ................................ ................................ ......... 9-14
9.3.2 Evaluation of Effectiveness ................................ ................................ .............. 9-14 – Plan Adoption, Submittal, and Implementation ................................ ...... 10-1
10.1 Inclusion of All 2025 Data ................................ ................................ ......................... 10-1
10.2 60-Day Notification ................................ ................................ ................................ ... 10-1
10.3 Notice of Public Hearing ................................ ................................ ........................... 10-1
10.4 Public Hearing and Adoption ................................ ................................ .................... 10-2
10.5 Plan Submittal ................................ ................................ ................................ .......... 10-2 DRAFT
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10.6 Public Availability ................................ ................................ ................................ ...... 10-3
10.7 Amending an Adopted UWMP and WSCP ................................ ............................... 10-3
LIST OF APPENDICES
Appendix A: Postings and Notifications for UWMP and WSCP Preparation Appendix B: City of Sunnyvale Detailed Demographic Data Appendix C: BAWSCA’s Regional Water Demand and Conservation Projections Appendix D: Projected Demands Provided to Wholesale Agencies Appendix E: SBX7-7 Compliance
Appendix F: 2021 Santa Clara Valley Water District Groundwater Management Plan Appendix G: Water Conservation Plan
Appendix H: SFPUC and Valley Water Drought Analyses Documents Appendix I: City of Sunnyvale’s Annex Within Volume II of the 2023 Santa Clara County Multijurisdictional Hazard Mitigation Plan
Appendix J: Sunnyvale Municipal Code
Appendix K: Sunnyvale’s Fiscal Year 2024/2025 Utility Fee Schedule Appendix L: Resolution for Adoption of the UWMP and WSCP Appendix M: Required 2025 UWMP Tables
Appendix N: 2025 UWMP Checklist
LIST OF FIGURES
Figure 3-1: City of Sunnyvale Service Area Map ................................ ................................ ..... 3-7 Figure 4-1: Annual Water Production 1995-2025 (AFY) ................................ .......................... 4-3 Figure 4-2: Potable and Non-Potable Water Demands by Sector 2015 to 2025 (AFY) ............ 4-5 Figure 6-1: Santa Clara County Groundwater ................................ ................................ ......... 6-4 Figure 6-2: Existing and Potential Recycled Water Distribution System ................................ 6-12 Figure 6-3: Percentage of Water Supply Sources (2025) ................................ ...................... 6-16
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2025 Urban Water Management Plan
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LIST OF TABLES
Table 2-1: Public Water System ................................ ................................ .............................. 2-1 Table 2-2: Supplier Identification ................................ ................................ ............................. 2-2 Table 2-3: Plan Identification ................................ ................................ ................................ ... 2-2 Table 2-4: List of Notified Agencies ................................ ................................ ......................... 2-3 Table 3-1: Local Climate Data ................................ ................................ ................................ . 3-2 Table 3-2: Population Projections for City of Sunnyvale ................................ .......................... 3-3 Table 3-3: Population by Race for City of Sunnyvale................................ ............................... 3-4 Table 4-1: Progress Toward 2028 Water Loss Standard ................................ ......................... 4-4 Table 4-2: Water Loss Audit Reporting ................................ ................................ ................... 4-4 Table 4-3: 2025 Demands for Potable and Non-Potable Water ................................ ............... 4-5 Table 4-4: Projected Potable and Non-Potable Water Use by Customer Type (AFY) .............. 4-7 Table 4-5: Projected Passive Water Conservation Savings ................................ ..................... 4-7 Table 4-6: Inclusion in Water Use Projections ................................ ................................ ......... 4-8 Table 4-7: Low-Income Estimated Current and Projected Water Use (AFY) ........................... 4-8 Table 5-1: 2020 Compliance with SBX7-7 ................................ ................................ ............... 5-1 Table 6-1: Past and Current Groundwater Volume Pumped (AFY) ................................ ......... 6-5 Table 6-2: Wastewater Collected within Service Area in 2025 (AFY) ................................ ...... 6-8 Table 6-3: Wastewater Treatment and Discharge Within Service Area in 2025 ....................... 6-8 Table 6-4: Current/Projected Recycled Water Direct Beneficial Uses within Service Area..... 6-10 Table 6-5: 2020 UWMP Recycled Water Use Projection Compared to 2025 Actual (AFY) .... 6-10 Table 6-6: Methods to Encourage Future Recycled Water Use (AFY) ................................ ... 6-13 Table 6-7: Transfer and Exchange Opportunities ................................ ................................ .. 6-15 Table 6-8: 2025 Water Supplies – Actual (AFY) ................................ ................................ .... 6-16 Table 6-9: Water Supplies – Projected (AFY) ................................ ................................ ........ 6-17 Table 6-10: Energy Usage for Calendar Year 2025 ................................ ............................... 6-18 Table 7-1: SFPUC Tier 1 Drought Allocations ................................ ................................ ......... 7-8 Table 7-2: Basis of Water Year Data ................................ ................................ ..................... 7-17 Table 7-3: Normal Year Supply and Demand Comparison (AFY) ................................ .......... 7-18 Table 7-4: Single Dry Year Supply and Demand Comparison (AFY) ................................ ..... 7-19 Table 7-5: Multiple Dry Years Supply and Demand Comparison (AFY) ................................ . 7-20 Table 7-6: Anticipated Percent Supply Reduction from Wholesale Suppliers ........................ 7-22 Table 7-7: SFPUC Tier 1 Drought Allocations ................................ ................................ ....... 7-23 Table 7-8: Five-Year Drought Risk Assessment ................................ ................................ .... 7-26 DRAFT
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2025 Urban Water Management Plan
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Table 8-1: Projected Potable and Non-Potable Water Use by Customer Type (AFY) .............. 8-2 Table 8-2: Water Supplies – Projected (AFY) ................................ ................................ .......... 8-6 Table 8-3: Basis of Water Year Data ................................ ................................ ....................... 8-7 Table 8-4: Water Service Reliability Supply and Demand Comparison ................................ ... 8-8 Table 8-5: Five-Year Drought Risk Assessment ................................ ................................ ...... 8-9 Table 8-6: Assessment Completion Timeline ................................ ................................ ........ 8-12 Table 8-7: SFPUC Retail and Wholesale RWS Allocations during System-wide Shortage .... 8-14 Table 8-8: Valley Water’s WSCP Six Standard Shortage Stages ................................ .......... 8-15 Table 8-9: Water Shortage Response Actions................................ ................................ ....... 8-16 Table 8-10: Water Shortage Contingency Plan Levels ................................ .......................... 8-17 Table 8-11: Demand Reduction Actions ................................ ................................ ................ 8-19 Table 8-12: Supply Augmentation and Other Actions ................................ ............................ 8-21 Table 8-13: Water Use Monitoring Mechanisms ................................ ................................ .... 8-22 Table 8-14: Summary of Actions for Catastrophic Events ................................ ..................... 8-24 Table 8-15: Notification to Cities and Counties ................................ ................................ ...... 8-33 Table 9-1: Demand Management Measures (DMMs) ................................ .............................. 9-1 Table 10-1: Notification to Cities and Counties ................................ ................................ ...... 10-2
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2025 Urban Water Management Plan
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ACRONYMS AND ABBREVIATIONS
AB Assembly Bill
ABAG Association of Bay Area Governments
ACS American Community Survey
ACWD Alameda County Water District
AF acre-feet, acre-foot
AFU affordable rental units
AFY acre-feet per year
AWIA America's Water Infrastructure Act
AWSP Alternative Water Supply Planning
AWWA American Water Works Association
BAIRWMP Bay Area Integrated Regional Water Management Plan BARDP Bay Area Regional Desalination Project
BARR Bay Area Regional Reliability
BAWSCA Bay Area Water Supply and Conservation Agency
BayQWEL Bay Area Qualified Water Efficient Landscaper Training BMR below market rate
Cal Water California Water Service Company
CalWEP California Water Efficiency Partnership
CAP 1.0 Sunnyvale’s 2014 Climate Action Plan
CCAP Climate Change Action Plan
CCF hundred cubic feet
CCWD Contra Costa Water District
CII commercial, industrial, and institutional
City City of Sunnyvale
CMIP5 Coupled Model Intercomparison Project Phase 5
Corps Army Corps of Engineers
COVID-19 Coronavirus
CPC California Plumbing Code
CVP Central Valley Project
CWRMP Countywide Water Reuse Master Plan
DCR Delivery Capability Report
DDW State Water Resources Control Board, Division of Drinking Water DRAFT
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ACRONYMS AND ABBREVIATIONS
Demand Study BAWSCA Regional Water Demand and Conservation Study, December 2025
DEOP Division Emergency Operations Plan
DMMs demand management measures
DOF Department of Finance
DOSD Division of Safety of Dams
DRA drought risk assessment
DSS Model Demand Side Management Least Cost Planning Decision Support System model
DWR Department of Water Resources
EBMUD East Bay Municipal Utilities District
EIR Environmental Impact Report
EO education outreach
EOC Emergency Operations Center
EOP Emergency Operations Plan
ERP Emergency Response Plan
ESSU Emergency Services and Security Unit
FEMA Federal Emergency Management Agency
ft feet, foot
FY fiscal year
GHG greenhouse gas
GMP Groundwater Management Plan
gpcd gallon per capita per day
gpf gallon(s) per flush
GSA Groundwater Sustainability Agency
GSI green stormwater infrastructure
GSP Groundwater Sustainability Plan
GSR Groundwater Storage and Recovery
Guidebook Final Draft 2020 Urban Water Management Plans: Guidebook for Urban Water Suppliers
HET high-efficiency toilet
HEU high-efficiency urinal
HHLSM Hetch Hetchy and Local Simulation Model
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2025 Urban Water Management Plan
Table of Contents
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ACRONYMS AND ABBREVIATIONS
HydroScience HydroScience Engineers, Inc
IPCC International Panel on Climate Change
IRP Infrastructure Reliability Plan
ISG Individual Supply Guarantee
ITR industrial to residential
JPA Joint Powers Authority
kWh kilowatt-hour
L2L Graywater Laundry to Landscape
LCSD Lower Crystal Springs Dam
LHMP Local Hazard Mitigation Plan
LOS Level of Service
LTVA Long Term Vulnerability Assessment
LVE Los Vaqueros Reservoir Expansion
MAP Monitoring and Assessment Program
MCL maximum contaminant level
MGD million gallons per day
MID Modesto Irrigation District
MMWD Marin Municipal Water District
MRP Municipal Regional Stormwater Permit
NPDES National Pollutant Discharge Elimination System
NPDWR National Primary Drinking Water Regulation
OCF Our City Forest
OES Office of Emergency Services
PFAS Per- and Polyfluoroalkyl Substances
Playbook Sunnyvale's Climate Action Playbook
PRSV pre-rinse spray valves
psi pounds per square inch
RCP representative concentration pathways
RGSR Regional Groundwater Storage and Recovery
RWJC Recycled Water Joint Committee
RWS City and County of San Francisco's Regional Water System SB Senate Bill
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2025 Urban Water Management Plan
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ACRONYMS AND ABBREVIATIONS
SBX7-7 Senate Bill Seven of the Senate’s Seventh Extraordinary Session of 2009
SCADA supervisory control and data acquisition
SCVURPPP Santa Clara Valley Urban Runoff Pollution Prevention Program SFPUC San Francisco Public Utilities Commission
SGMA Sustainable Groundwater Management Act
SMaRT® Station Sunnyvale Materials Recovery and Transfer Station sq ft square feet
State State of California
STORMS Strategy to Optimize Resource Management of Stormwater SVCE Silicon Valley Clean Energy
SVCW Silicon Valley Clean Water
SWAP Shared Water Access Program
SWP State Water Project
SWRCB State Water Resources Control Board
TID Turlock Irrigation District
U.S. United States
USBR U.S. Bureau of Reclamation
USD Union Sanitary District
USEPA United States Environmental Protection Agency
UWMP Urban Water Management Plan
UWUO Urban Water Use Objective
Valley Water Santa Clara Valley Water District
WEAP Water Evaluation and Planning
WPCP, Plant Sunnyvale's Water Pollution Control Plant
WRPS Wolfe Road Pump Station
WSA Water Supply Agreement between the City and County of San Francisco and Wholesale Customers in Alameda County, San Mateo County and Santa Clara County
WSAP Water Shortage Allocation Plan
WSCP Water Shortage Contingency Plan
WSIP Water System Improvement Program
WSMP Water Supply Master Plan
DRAFT
Attachment 1
City of Sunnyvale
2025 Urban Water Management Plan
SECTION 1 – Introduction and Overview
www.hydroscience.com
– INTRODUCTION AND OVERVIEW
The City of Sunnyvale’s (City) 2025 Urban Water Management Plan (UWMP) was prepared to provide a comprehensive update to the 2020 UWMP, which was adopted by City Council on June 29, 2021. The 1983 California Urban Water Management Act (Act), also referred to as Assembly Bill (AB) 797, requi res all urban water suppliers (Suppliers) who directly serve 3,000 or more customers or who provide 3,000 or more acre-feet of water per year (AFY), to prepare a UWMP every five years.
The UWMP will enable the Department of Water Resources (DWR) to make projections on water usage and determine the status of water conservation efforts throughout the State. Although the efficient use of water supplies is a statewide concern, the planning and implementation of such use can best be accomplished at the local level.
The 2025 update to the City’s 2020 UWMP builds upon previous updates, incorporates relevant water management issues, addresses supply and demand projections within the City for the next 20 years, and presents future water supply reliability . It demonstrates compliance with State legislative mandates that have been enacted, in particular Senate Bill (SB) X7 -7 Water Conservation Act of 2009, AB 1420 Water Demand Management Measures, and 2018 Water Conservation Legislation AB 1668 (Friedman) and SB 606 (Hertzberg).
SBX7-7 targeted a 20% water use reduction per capita by December 31, 2020 , and required Suppliers to identify their base daily per capita water use (baseline), urban water use target, interim water use target, and compliant daily per capita water use . The City demonstrated compliance with SBX7 -7 in 2020, as documented in the 2020 UWMP. The 2018 Water Conservation Legislation AB 1668 and SB 606 established additional requirements for the UWMP, including requiring Suppliers to develop and adopt a standalone Water Shortage Contingency Plan (WSCP).
The 2025 UWMP must also include information on water deliveries and uses; water supply sources; efficient water uses; and demand management measures, including implementation strategy and schedule. DWR is responsible for reviewing the UWMP and determining whether it addresses the requirements of the Act. A current UWMP is required to be eligible for a water management grant or loan administered by the State including DWR, the State Water Resources Control Board (SWRCB), or the Delta Stewardship Council.
The goals of the 2025 UWMP update include:
• To provide a valuable resource tool to be used by policy makers at City, County, and local government levels to facilitate making sound and consistent decisions relating to water management and regional growth in the area.
• To meet all Federal and State regulatory requirements. • To update the City’s water conservation plan and projections for future conservation efforts. • To prepare a realistic Drought Risk Assessment.
• To update the City’s Water Shortage Contingency Plan and Seismic Risk Assessment and Mitigation Plan.
• To calculate water service energy usage.
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2025 Urban Water Management Plan
SECTION 1 – Introduction and Overview
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• To identify communication links between key departments at both City and County levels, and to strengthen ties for cooperatively addressing water supply and land use planning issues. • To continue to solidify relationships with other retailers and wholesalers to address regional issues concerning water supply and demand.
1.1 Lay Description
The City owns, operates, and maintains a drinking water system that serves its approximately 160,000 residents. Most of the City’s water comes from treated surface water from two wholesalers: the San Francisco Public Utilities Commission (SFPUC) and Santa Clara Valley Water District (Valley Water). The remainder of the City’s water is comprised of groundwater from six City-owned wells. The City also owns and operates a recycled water system that supplies water for irrigation to some customers in the City . The recycled water is produced at the City’s Water Pollution Control Plant (WPCP or Plant). The City’s water demand projections have been updated in this 2025 UWMP to reflect population growth, planned development, water conservation estimates, and the anticipated effects of climate change. Water demands within City boundaries are expected to increase from 18,806 acre -feet per year (AFY) in 2025 to approximately 29,014 AFY in 2045.
There are several factors in determining the City’s water supply reliability. In December 2018, the SWRCB adopted amendments to the Water Quality Control Plan for the San Francisco Bay/Sacramento-San Joaquin Delta Estuary (Bay -Delta Plan Amendment) to est ablish water quality objectives with the stated goal of increasing salmon populations in three San Joaquin River tributaries (the Stanislaus, Merced, and Tuolumne Rivers) and the Bay-Delta. It remains unclear how or if the Bay -Delta Plan Amendment will be implemented. This UWMP assumes the Bay - Delta Plan Amendment will be implemented in 2030, consistent with SFPUC’s 2025 UWMP , leading to cutbacks in projected wholesaler supplies. SFPUC expects that some of these cutbacks will trickle down to its retailers, including the City. Even with some expected cutbacks by SFPUC and Valley Water, based on the information provided by both wholesalers, the City will be able to meet projected water demands under normal, single-dry, and five consecutive dry-year conditions both in the near term and long term (through 2040). The City only anticipates shortfalls up to 4% during a multi-year drought beginning in 2045.
The City will work closely with SFPUC, Valley Water, and other water retail agencies to implement any stages of action as appropriate to reduce the demand for water during water shortage conditions. The City’s WSCP describes the City’s approach and response in the event of a water shortage ranging from 10% to greater than 50%. If a shortage is identified, the WSCP outlines the appropriate response actions, such as restrictions on irrigation and expanding public information campaigns, and relevant enforcem ents to mitigate the shortage. In the event of a decrease of local supplies, the City would respond by implementing demand reduction strategies outlined in this UWMP in line with the severity of the supply shortage. Thus, any supply deficits would be compensated for by increased conservation and restrictions in consumption, if needed.
DRAFT
Attachment 1
City of Sunnyvale
2025 Urban Water Management Plan
SECTION 2 – Plan Preparation
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– PLAN PREPARATION
The UWMP was prepared in accordance with the Final 2025 Urban Water Management Plan Guidebook dated January 2026 (Guidebook). The City retained HydroScience Engineers , Inc. (HydroScience) to prepare the 2025 UWMP update. HydroScience worked closely with the City’s Environmental Services Department during the development of the UWMP to assure accurate and updated information was collected and incorporated . Based on the number of municipal connections as shown in Table 2-1, the City is required to prepare an update to the 2020 UWMP.
Table 2-1: Public Water System
Public Water System
Number
Public Water System
Name
Number of Municipal
Connections 2025
Volume of Water
Supplied 20251
CA4310014 City of Sunnyvale 28,514 18,806
Note:
1. Volume of water in acre-feet (AF) supplied within City limits.
The UWMP organization and coordination efforts are detailed below.
2.1 Plan Organization
The 2025 UWMP is organized as recommended in the Guidebook to expedite review and approval by DWR. The sections contained in the 2025 UWMP are as follows:
• Section 1 – Introduction and Overview
• Section 2 – Plan Preparation
• Section 3 – System Description
• Section 4 – Water Use Characterization
• Section 5 – SBX7-7 Baselines and Targets
• Section 6 – Water Supply Characterization
• Section 7 – Water Supply Reliability and Drought Risk Assessment • Section 8 – Water Shortage Contingency Plan
• Section 9 – Demand Management Measures
• Section 10 – Plan Adoption, Submittal, and Implementation
2.2 Inclusion of All 2025 Data
The 2025 UWMP includes all data for water use and planning for the calendar year of 2025. Data is shown in calendar year with units in acre-feet (AF) (Table 2-2).
DRAFT
Attachment 1
City of Sunnyvale
2025 Urban Water Management Plan
SECTION 2 – Plan Preparation
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Table 2-2: Supplier Identification
Supplier and UWMP Format
Type of Supplier
Supplier is a wholesaler
X Supplier is a retailer
Fiscal or Calendar Year
X UWMP Tables are in calendar years
UWMP Tables are in fiscal years
Units of measure used in UWMP
Unit Acre-Feet (AF)
2.3 Coordination
This UWMP was developed as an individual UWMP ( Table 2-3) but included coordination with several regional partners.
Table 2-3: Plan Identification
Select Only One Type of Plan
X Individual UWMP
Water Supplier is also a member of a RUWMP
Water Supplier is also a member of a Regional Alliance
Regional Urban Water Management Plan (RUWMP)
The City participates in area and regional planning with the Bay Area Water Supply and Conservation Agency (BAWSCA), SFPUC, and Valley Water. The City also participates in basin- wide groundwater and conservation planning with Valley Water . Valley Water provides management of local groundwater resources and contracts for imported water to Santa Clara County. Participation in these planning efforts helps ensure that the City will receive an adequate amount of water to provide for its residents and businesses. It also provides for drought-condition planning and coordination with the rest of the region so that no water provider is unduly impacted by lack of water.
BAWSCA provides regional water reliability planning and conservation programming for the benefit of its 26 member agencies that purchase wholesale water supplies from SFPUC .
Collectively, the BAWSCA member agencies deliver water to over 1.8 million residents and nearly 40,000 commercial, industrial, and institutional accounts in Alameda, San Mateo, and Santa Clara Counties.
BAWSCA also represents the collective interests of these wholesale water customers on all significant technical, financial, and policy matters related to the operation and improvement of the SFPUC’s Regional Water System (RWS).
BAWSCA’s role in the development of the 2025 UWMP updates is to work with its member agencies and the SFPUC to seek consistency among UWMP documents. The City contacted the DRAFT
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SFPUC (through BAWSCA) and Valley Water for assistance with its UWMP and at the same time provided those agencies with pertinent data for their own plans.
The City encouraged the involvement of social, cultural, and economic community groups during the preparation of the 2025 UWMP. Specific efforts were made to send out a public notification mailer to all community groups, including public and private water suppliers. BAWSCA agencies were notified of the 2025 preparation process. The City directed these agencies to the location of the Draft UWMP and solicited comments and suggestions.
The City published its intention to update the 2020 UWMP and invited public comments on the City’s Web page. Copies of notices for participation in the 2025 UWMP preparation can be found in Appendix A.
A Notice of Preparation of the UWMP was sent on February 2, 2026 to the following agencies listed in Table 2-4.
Table 2-4: List of Notified Agencies
Agency Name
Alameda County Water District Santa Clara Valley Water District City of Hayward Mid-Peninsula Water District
City of Milpitas North Coast County Water District
City of Mountain View City of East Palo Alto
City of Palo Alto Westborough Water District
City of Santa Clara California Water Service Company
Stanford University San Jose Water Company
Purissima Hills Water District City of San Jose
City of Brisbane City of San Bruno
City of Burlingame Coastside County Water District
City of Daly City City of Foster City
Town of Hillsborough County of Santa Clara
City of Menlo Park Bay Area Water Supply & Conservation Agency City of Millbrae
San Francisco Public Utilities Commission
City of Redwood City
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– SYSTEM DESCRIPTION
This section provides information about the City and service area including the organization structure and history, climate, demographics, and the water distribution system.
3.1 History
The City of Sunnyvale is in Santa Clara County, just minutes from the City of San José and approximately 40 miles south of the City and County of San Francisco . The City of Sunnyvale was incorporated in 1912 and became an official charter city in 1950 . When the City was incorporated in 1912, its population was approximately 1,500 and the entire municipal water system relied exclusively on groundwater for its potable water supply source. The original water supply source was from a privately -owned well at the Joshua Hendy Iron Works Factory in Sunnyvale. By 1926, a total of three wells were operational, none of which are in use today .
During World War II, the Federal government awarded several war contracts that led to the development of the Central Wate r Plant and groundwater well , which were more recently decommissioned.
At the close of World War II, Sunnyvale began to grow very quickly. By the early 1950s, demand for water surpassed the supplies available from groundwater and led to overdraft of the aquifers.
As a direct consequence of the overdraft of the groundwater, land subsidence in the northern region of the City was at 0.3 feet per year . By 1952, the population had grown to 10,000, and it was at that time that Sunnyvale entered into a contractual agreement with the City and County of San Francisco for delivery of imported SFPUC water. That same year, three connections were made to the SFPUC supply to serve as a primary water source, to be supplemented by additional City-owned and operated wells located throughout the City at that time . In the 17 years that followed, the City population grew to 96,000. Sunnyvale realized the need for an additional water supply source and contracted with Valley Water for two connections to the Valley Water’s West Pipeline. By 1970, the City had developed three of its four current water supply sources (SFPUC/Hetch Hetchy, Valley Water Central Valley Project water, and City-owned wells).
As the demand for water was steadily on the rise during the period of 1970 through the mid-1980s, the City expanded the number of Hetch Hetchy connections to its current total of six. Sunnyvale also added two well water producing facilities, which gave the City a total of 11 City -owned and operated wells at that time.
The City also expanded its interconnections with surrounding water utilities in the immediate area to ensure a sustainable water supply during times of emergencies, thus adding to the system’s reliability. The City has, at the present time, connections to the cities of Mountain View, Cupertino, and Santa Clara, as well as to the California Water Service Company.
The City’s water demand reached an all-time high in 1987 and demand was expected to increase, reaching approximately 36,000 AFY at the projected system build-out. The six-year drought that started in the late 1980s and ended in the mid-1990s brought about many changes in water usage, which came largely from the industrial sector . Conservation measures and a recycled water program adopted by the City were some of the most important drought -induced changes .
Changes in the economic dynamics of the area occurring after 2001 brought about new reductions to water demand. Current projections for the water system build -out expect a slow increase to less than 30,000 AFY over the next 30 years.
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3.2 Organization Structure
The City operates under a Council-manager form of government. Council, as the legislative body, represents the entire community and is empowered by the City Charter to formulate citywide policy. Six Council members are elected by District by City voters for numbered seats and serve four-year terms. The mayor is elected city-wide by the voters. The City Charter limits the Mayor and Council members to serving two consecutive terms. The Vice Mayor is selected from among the ranks of the Council . The City Manager is appointed by Council and serves as the Chief Executive Officer, responsible for day-to-day administration of City affairs and implementation of Council policies. Boards and commissions, through public meetings, advise the City Council on policy issues. The City Council meetings are open to the public with few exceptions as allowed by law and take place between one and four Tuesdays per month.
The City’s water utility is managed, operated, and maintained by the Water and Sewer Division in the Environmental Services Department. This Division is responsible for the purchase and distribution of potable and non -potable water as well as construction of new and replacement infrastructure.
3.3 Climate
The City enjoys a generally mild, temperate climate with relatively low levels of precipitation .
Daytime temperatures range from the mid 80’s during the summer to typically not less than 45°F in the winter. Climate information for the area is illustrated in Table 3-1.
Table 3-1: Local Climate Data
Parameter Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Tot/ Avg
Monthly Average
ETo (inches)1,2 1.38 1.94 3.21 4.45 5.48 6.10 6.34 5.60 4.41 3.14 1.68 1.25 44.98 Precipitation
(inches)3 4.7 4.0 3.7 1.7 0.7 0.1 0.0 0.0 0.2 1.1 2.5 4.3 23.0 Average Max
Temperature (°F)3 55.1 57.7 60.7 65.3 71.2 78.2 83.2 82.7 80.4 73.3 62.9 55.8 68.9 Average Min
Temperature (°F)3 37.3 39.0 40.2 42.1 46.5 51.1 55.3 55.2 53.2 48.3 41.5 37.4 45.6 Average
Temperature (°F)3 46.2 48.4 50.5 53.7 58.9 64.6 69.2 68.9 66.8 60.8 52.2 46.6 57.2 Notes:
1. ETo = Evapotranspiration is the loss of water to the atmosphere by the combined processes of evaporation (from soil and plant surfaces) and transpiration (from plant tissues).
2. 2001-2025 data from California Irrigation Management Information System (CIMIS) Station 171 – Union City.
3. 1895-2025 data for Santa Clara County from the National Oceanic and Atmospheric Administration (NOAA).
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3.3.1 Climate Change Impacts
Several scientific reports have confirmed that greenhouse gas (GHG) emissions from human activities are contributing to a progressively warming climate . A slight increase in global temperatures could cause several environmental impacts, including increased wildfires, reduced snowpack, sea level rise, intensifying droughts and storms, and shorter and more intense water seasons. Some climate change effects are already apparent in the State . Precipitation in the Bay Area has had high variability each year, leading to some very wet years and some very dry years. This variability is expected to continue, leading to potential changes in water supply and management. Additionally, the State is predicted to experience longer and deeper droughts due to increasing temperatures, which could pose a significant challenge to water supply reliability.
The City has consistently incorporated sustainability and climate action into their goals and planning efforts to address these potential threats. In 2014, the City created the Climate Action Plan (CAP 1.0) to set sustainability goals and outline strategies to reduce emissions . The City built on CAP 1.0 and adopted a new Climate Action Playbook in 2019 along with Game Plan 2022, which identified a three-year work plan of specific actions to help the City meet State level targets for carbon neutrality. The most recent update of the 2019 plan is the June 2024 Climate Action Playbook Update and Game Plan 2028 (Playbook), available at the following link:
https://www.sunnyvale.ca.gov/home/showpublisheddocument/1066/638606111674670000. The Playbook identifies an updated five-year work plan of strategies and actions to continue progress towards the State level GHG emissions reduction targets, which include:
• 1990 levels by 2020 (AB 32, 2006)
• 40% below 1990 levels by 2030 (SB 32, 2016)
• 80% below 1990 levels by 2050 (Executive Order S-3-05, 2005) The City has already met the 2020 emissions goal and has several emission reducing actions in place to meet 2030 levels . The Playbook outlines strategies to meet the 2050 goal, including promoting clean electricity, decarbonizing buildings, decarbonizing transportation, sustainable land use, and managing resources sustainably.
3.4 Service Area Population
The City currently provides water service to a population of 159,673 people. Since the City’s service area overlaps the City boundaries by more than 95%, the 2025 population estimate was sourced from the 2025 Department of Finance (DOF) E-5 Population and Housing Estimates for Cities. According to the DOF data, the average annual population growth rate between 2010 and 2025 is approximately 0.88%. This rate was used to project the population of the water service area through 2045. As shown in Table 3-2, city population is projected to increase approximately 19% in the next 20 years.
Table 3-2: Population Projections for City of Sunnyvale 2025 2030 2035 2040 2045
City Population1 159,673 166,813 174,272 182,065 190,206 Note:
1. Department of Finance 2025 estimate and 2030-2045 projections based on the 2010-2025 historical annual growth rate of 0.88%.
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3.5 Demographics
The City is a diverse community with a residential population of 159,673. Approximately 60% of residents speak a language other than English at home . The percent population by race is summarized in Table 3-3.
Table 3-3: Population by Race for City of Sunnyvale
Race Percent
Asian alone 49.6%
White alone 28.4%
Black or African American alone 1.6%
Native American and Alaska Native alone 0.6%
Native Hawaiian and Other Pacific Islander alone 0.4%
Some other race alone 9.5%
Two or more races 9.9%
Source: 2020-2024 American Community Survey 5-Year Narrative Profile According to the 20 20-2024 American Community Survey (ACS) 5 -Year Narrative Profile, t he City’s median household income is estimated to be $186,170, which is one of the highest in the nation. The City has a solid economic base, and poverty levels in the City have remained consistently lower than those of Santa Clara County or the State . Residents are generally well educated, with approximately 69% having a bachelor’s degree or higher. With its Silicon Valley location, the City has a n established high-tech presence having transitioned from agricultural to defense to the current high-tech economy. It has remained on the cutting edge of Silicon Valley’s innovation. According to the City’s July 2025 Business License Database, the number of firms in the City is estimated to be 6,978. The top industries in the City include professional, scientific , management, and administrative and waste management services (2 9.0%); manufacturing (15.7%); education services, health care and social assistance (14.3%); information (12.7%); and retail trade (8.1%). The City is home to growing clusters of emerging technology companies in the high-tech and biotechnology industries.
3.5.1 Low-Income Housing
In December 2023, the City adopted the 2023-2031 Housing Element (Housing Element), which provides a roadmap for the City to address current and projected housing needs. Per the Housing Element, there were approximately 55,424 housing units in the City in 2023. Based on the 2021 Association of Bay Area Governments (ABAG) projections, the City is estimated to need an additional 11,966 housing units through the year 2030.
Over 1, 800 City housing units are designated as low -income housing. The City has actively supported affordable rental housing utilizing a variety of local, State, and Federal funds, and works extensively with non-profit housing developers in the ownership and management of its projects.
Rent-restricted housing in Sunnyvale includes both publicly subsidized affordable housing, generally assisted with any combination of Federal, State, local, and/or private subsidies, and deed-restricted rental units provided through the City’s Below Market Rate (BMR) program. The City’s BMR program currently requires that a percentage of units within some market-rate rental properties be offered at BMR rent for lower -income residents . Lower-income residents are DRAFT
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defined as households at 80% of the Area Median Income . Very low-income residents, defined as households at 50% of the Area Median Income, can take advantage of a subset of BMR units referred to as Affordable Rental Units (ARUs). Additional detailed demographic data can be found in Appendix B.
3.6 Land Uses within Service Area
The City service area encompasses approximately 24 square miles. Although the City is mostly built-out, factors such as population growth and climate change call for changes in the City’s land use over time. The 2024 Update to the Land Use and Transportation Section of the Sunnyvale General Plan identified areas of the City that will be preserved, enhanced, and transformed over a 20-year planning horizon (Horizon 2035). Preserved and enhanced areas are expected to have minor upgrades but no major character shift. Transformed areas include older shopping centers and office areas that will be transformed into new mixed-use developments called Village Centers.
The Village Centers are meant to provide residential diversity in existing residential areas . On July 1, 2025, the City adopted the Village Center Master Plan (VCMP), which outlines a detailed framework to facilitate the continued development of Village Center sites.
As part of the 1993 “Industrial to Residential” program (ITR), the City has encouraged specific industrial areas to redevelop to residential use. Each ITR site allows industrial, office, commercial, and residential uses to exist within the same district while gradually converting to residential use.
As of 2007, ITR designated sites totaled approximately 320 acres, accommodating up to 7,700 dwelling units. Moffett Park is one of the City’s largest employment centers and is the newest area in the City planned for transition from industrial to residential. The Moffett Park Specific Plan was adopted in July 2023.
3.7 Water Supply Sources
The City has three sources of potable water supplies : purchased water from SFPUC, treated purchased water from Valley Water, and City-owned and operated groundwater wells. In addition, the City has multiple potable water interties with the City of Santa Clara, the City of Mountain View, the City of Cupertino, and the California Water Service Company (Cal Water), which can all provide water service in the event of an emergency . The City also has a recycled water program that supplies water treated at the City’s WPCP for non -potable purposes such as landscape irrigation and watering golf courses.
3.8 Distribution System
The City retails potable drinking water and non-potable (recycled) water within the City limits. The City also wholesales recycled water through a developed recycled water program in partnership with Valley Water. Recycled water pipelines serve communities both within and beyond city limits.
Cal Water retails potable drinking water from Cal Water owned groundwater wells in pocket areas of the City (see Figure 3-1).
The City owns, operates, and maintains a water supply and distribution system worth more than $200 million . The system is a closed network consisting of three different pressure zones .
Sunnyvale’s elevation varies from sea level at the northern end of town to approximately 300 feet above sea level at the southwest corner of town . Zone I extends roughly from El Camino Real DRAFT
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northward to the San Francisco Bay and is supplied primarily by SFPUC water. Zone II consists of everything south of Zone I except for the southwest corner of the City and is served by a supply mixture of SFPUC water, City groundwater wells, and Valley Water treated water. Zone III serves the southwest section of town with Hollenbeck Avenue on the east side and Fremont Avenue on the north side and is served by a combination of Valley Water treated water and City well water.
The conveyance system extends approximately 339 miles in length, with pipe diameters ranging from 4 inches to 36 inches.
Water pressure within the distribution system is maintained within a range of 40 pounds per square inch (psi) to 105 psi throughout all three zones . A Supervisory Control and Data Acquisition (SCADA) system allows the City to maintain a balanced system, generally keeping water deliveries between those pressure readings . The average operating pressure is 68 psi .
Zone I receives direct downstream pressure from the SFPUC pipeline system with an operating pressure of approximately 130 psi in the winter and 120 psi in the summer, though that pressure is reduced by pressure regulating valves before it is delivered to customers.
Several pocketed areas within the City boundaries, located primarily along Fremont Avenue and Sunnyvale-Saratoga Road, receive water from Cal Water. These areas were at one time part of unincorporated Santa Clara County, but have since been annexed by the City . Cal Water produces its own water from wells the company owns exclusively. The City, through a cooperative effort, provides emergency connections to Cal Water’s system to improve fire flows when needed.
There are eight active potable water storage reservoirs at four different locations throughout the City with a total storage capacity of 26.5 million gallons (81 AF). There is also one recycled water reservoir with a storage capacity of 1.5 million gallons (4.7 AF). This volume of water can meet at least one day of average water demand during the summer for the entire City.
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Attachment 1
Villa St
W Mid dlefiel
d Rd
Shoreline Golf
Links
M ount ain
V iew
Gra
nger Ave
Rancho San
Antonio County
Park
E Ar qu es A veW W ash ing ton Ave
E E
velyn Ave
E Evelyn
Ave
Kife r Rd
Fairch
ild Dr
N
Mary
Ave
Ca
ldero
n
Ave
W Evelyn Av
e
Manila Dr
N Borregas Ave
N W
ol
fe R
d
Tasman Dr
Gra
nt Rd
Moffett B
lvd
Cen tral Exp y
W El Cam
ino Real
La
wre
nce
Expy
W V
alley Fwy
Sunnyvale Golf
Course
Sunnyvale
Baylands
County Park
Moffett Federal
Airfield
South Shore
Port
S unnyvale
G2
Gra
pe
Ave
W Remington DrS Bernardo
Ave
Ir is Ave
Henderson Ave
The Dalles Ave
Reed AveLevin Ave
Oak Ave
Popla
rAve
Ca rlisle Way
Fa
llen
Le
af
Ln
B
elle
ville
W
ay
Crest
on
Dr
N Blaney
Av
e
N Stelling Rd
Grant Rd
Sunnyvale Saratoga Rd
W Fremont Ave
E Homestead Rd
N De Anza Blvd
EEl
Cam
ino R
eal
Lawre
nce Expy
Foothill
Expy
W
Valley F
wy
Calabazas Creek
Kifer Rd
Scott Blvd
Central Expy
Santa Clara Golf
and Tennis Club
Alviso
Nobili Ave
War burton
Ave
Ame
th
yst Dr
Benton St
Po
meroy Av
e
Woo
dh
ams
Rd
Monr oe St
Sa
n To
mas Expy
101
85 237
82 280
FIGURE 3-1
CITY OF SUNNYVALE
URBAN W
ATER MANAGEMENT PLAN
SERVICE AREA MAP
LEGEND
CITY LIMITS
ZONE I (SFPUC)
ZONE II (VALLEY WATER)
ZONE III (VALLEY WATER)
BLENDED AREA
CAL WATER SERVICE
0 2,250 4,500
1 IN = 4,500 FT
N
_
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– WATER USE CHARACTERIZATION
This section provides information on past, current, and projected water use within the City’s service area. Note that water use is provided on a calendar year basis.
4.1 Water Use Objectives
In 2018, California State Legislature and Governor Brown passed into law SB 606 (Hertzberg) and AB 1668 (Friedman) which were attributed from the Making Water Conservation a Way of Life Executive Order from 2016. The purpose of these bills is to improve water conservation and drought planning through the development of new standards for water use. In July 2024, California adopted regulations that established an annual Urban Water Use Objective (UWUO) for water suppliers and introduced Performance Measures for commercial, industrial, and institutional water users. The UWUO is a water -budget-based framework tailored to each Supplier based on their individual standards for the following components:
• Indoor residential water use;
• Outdoor residential water use;
• Commercial, industrial, and institutional water use for landscape irrigation with dedicated meters; and,
• Water loss.
Beginning in 2027, Supplie rs will be required to annually assess whether their total water use complies with their established UWUO. Some State standards will become progressively more stringent over time, which may require additional conservation efforts to achieve compliance .
Because compliance with the UWUO requirements is under the authority of the SWRCB, UWUO compliance projections are not required as part of this UWMP per the Guidebook. Therefore, UWUO projections are considered but not explicitly included herein, with the exception of the City’s water loss standard. Pursuant to the Water Code, the City has included data in Section
4.3.2 that demonstrates the City’s progress towards meeting its water loss performance standard.
4.2 Non-Potable Versus Potable Water Use
The City supplies both treated drinking water (potable) and recycled water (non -potable) to service area customers. Recycled water is supplied for non-potable purposes such as irrigation and toilet flushing . Potable water is available as a backup supply to supplement the recycled water system when needed. Although some potable water is used in the recycled water system, potable and recycled water are reported separately throughout this UWMP. Potable water supply totals include any potable water added to the recycled water system. Recycled water is discussed further in Section 6.
4.3 Past, Current, and Projected Water Use by Sector
The City of Sunnyvale categorizes its water accounts into six broad customer categories: single- family, multi-family, commercial (incorporating industrial), institutional, irrigation, and fire services.
The commercial sector includes all non-residential accounts that are not classified as irrigation or DRAFT
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institutional. These six sectors include all service area accounts and will be used to report past, current, and projected water use throughout this UWMP.
4.3.1 Historical Water Use
Water use varies depending on factors such as population, weather, policy change, and the economic climate . Recognizing these factors and long-term general trends in water use is valuable in projecting future supply needs. Historical water production is generally representative of water demand and can be used as a surrogate to quantify historical water use.
The City has three potable water supply sources: SFPUC, Valley Water, and groundwater wells.
In the 1990’s, the City modified its traditional sewer treatment plant to produce recycled water .
The City began using recycled water in 1999, supplementing the overall water supply.
Figure 4-1 is a graphical depiction of the total annual water supply in AFY categorized by supply source from 1995 to 20 25. The City purchases water from Valley Water and SFPUC, so the increase in deliveries from one source will generally be accompanied by a decrease from the other. Water use in Sunnyvale generally remained consistent from 1996 to 2001. After 2002, water use began to decline in response to drought -related conservation measures, economic factors, and contractual limitations previously negotiated . The sharp decline in water use from 2008 to 2011 and again from 2013 to 2015 was due to drought conditions and implementation of local and regional water conservation measures.
Water use increased from 2015 to 2020 , which can be attributed to recovery from the drought .
Although total water use in 2020 remained consistent with historical non-drought condition trends, demand patterns for 2020 were greatly affected by the Coronavirus (COVID-19) pandemic. The pandemic began in early 2020 and led to several Regional Shelter-In-Place/Stay-at-Home Orders and local emergency restrictions. Most non -essential businesses shifted to remote work, and several businesses were unable to contin ue operation due to the Stay-at-Home Orders. These conditions caused a shift in water demand from all sectors to predominantly residential use but did not have a significant effect on overall water use.
Water use declined again from 2020 to 2023 due to returning drought conditions and voluntary local and statewide water use reduction measures. Since 2023, water use has partially recovered as drought conditions have eased.
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4.3.2 Distribution System Water Loss
Water loss within the City’s distribution system may be due to leaks, breaks, malfunctioning valves, and water meter inaccuracies . Other losses come from legitimate uses such as water/sewer main and hydrant flushing, tests of fire suppression systems, and street cleaning .
SB 555, approved in October 2015, requires all water retailers to report distribution system losses annually based on the American Water Works Association’s (AWWA) Water Audit Software.
In accordance with SB 555 and the 2018 Water Conservation Legislation AB 1668 and SB 606 , the SWRCB adopted new water loss performance standards for Suppliers in October 2022. The regulation requires that the City monitor and reduce real water losses in accordance with the State established standard that was developed based on the City’s water system characteristics and historical water loss data. Compliance with the water loss performance standard is assessed based on water audit data submitted for the preceding three years. Although compliance begins January 1, 2028, t he City is required to report on its progress towards meeting its water loss performance standard in the 2025 UWMP. The water loss performance standard is composed of the following two parts:
• Real Water Loss Standard: Real losses are defined as physical water losses from the water distribution system and storage tanks, up to the customer meter.
Figure 4-1: Annual Water Production 1995-2025 (AFY)
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• Apparent Water Loss Standard : Apparent losses include inaccuracies associated with customer metering, systematic data handling errors, and unauthorized consumption.
The City’s water loss standards are summarized in Table 4-1. Table 4-1 also presents results from the most recent AWWA Water Loss Audit, completed for calendar year 2024, to demonstrate the City’s progress toward meeting the 2028 water loss standard.
Table 4-1: Progress Toward 2028 Water Loss Standard
Most Recent AWWA Water
Loss Audit (2024) 2028 State Water Board Standard
Number of
Service
Connections
Volume of
Real Loss
(AF)
Volume of
Apparent Loss
(AF)
Real
Water
Loss
(gpscd)
Apparent
Water
Loss
(gpscd)
Real Water
Loss
Standard
(gpscd)
Apparent
Water Loss
Standard
(gpscd)
29,717 1,509 255 45.3 7.7 29.4 7.9
Note:
1. gpscd = gallons per service connection per day.
The City met its apparent water loss standard in 2024 but did not meet the real water loss standard. However, real water loss in 2024 exceeded historical levels and represents an outlier compared to prior years. The water losses from 2020 to 2024 are summarized in Table 4-2. As seen in the data, total system losses were consistently between 7% and 8% of total water supplied prior to 2024, and real water loss historically remained below 40 gpscd. The City met both water loss performance standards in 2023, and real water loss is expected to match historical levels in the future.
Table 4-2: Water Loss Audit Reporting
Reporting Period
Start Date
(mm/yyyy)
Volume of Water
Loss (AFY)1
System Loss
Percentage2
Real Water Loss
(gpscd)
Apparent Water
Loss (gpscd)
01/2020 1,401 7% 34.1 8.2
01/2021 1,418 8% 35.0 7.7
01/2022 1,519 8% 38.5 7.5
01/2023 1,180 7% 28.0 7.4
01/2024 1,764 9% 45.3 7.7
Notes:
1. Values were reported to DWR in the City’s annual Water Loss Audit Reports , available at the following link:
https://wuedata.water.ca.gov/awwa_plans.
2. Percentage of water loss out of total water supplied each year.
The system loss projections and total demand projections contained in this UWMP assume a future system loss percentage of approximately 8%, which represents an average of actual system losses experienced by the City over the past five years. Saline water intrusion barriers, groundwater recharge, and conjunctive use are not included in water loss estimates for this UWMP since these uses are managed by Valley Water and are reflected in Valley Water’s UWMP for the entire County.
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4.3.3 Current Water Use
Table 4-3 presents the City’s 202 5 potable and non-potable water use within the City’s service area categorized by customer type, including estimated system losses. Figure 4-2 shows these demands compared to historic potable water use by customer type and total recycled water (non- potable) use from 2015 to 2025. Recycled water demands are discussed further in Section 6.
Table 4-3: 2025 Demands for Potable and Non-Potable Water Customer Type Potable or Non-Potable1 Volume (AFY)
Single Family Residential Potable 5,282
Multi-Family Residential Potable 5,348
Commercial/Industrial (combined) Potable 3,939
Institutional Potable 152
Landscape Irrigation Potable 2,132
Other (Firelines) Potable 8
System Losses2 Potable 1,304
Commercial/Industrial (combined, recycled water)3 Non-Potable 90 Landscape Irrigation (recycled water) Non-Potable 551
Subtotal Potable 18,165
Subtotal Non-Potable 641
Total 18,806
Notes:
1. Non-potable use includes recycled water and any potable water added to the recycled water system.
2. Water loss is estimated as the difference between actual water sales and water supplied.
3. Recycled water used for commercial dual plumbing and industrial cooling.
Figure 4-2: Potable and Non-Potable Water Demands by Sector 2015 to 2025 (AFY)
Note: Recycled water use includes services outside City limits, specifically Moffett Field and Apple® Campus 2.
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Total annual potable water use in 2025 was approximately 1,100 AF less than the projected 2025 water use from the previous UWMP . Overall demand increased from 2023 to 2025, which can be attributed to the relaxation of water rationing mandates and measures related to the drought.
As mentioned previously, water use in 2020 was affected by the COVID -19 pandemic .
Commercial water use in 2020 showed a significant decline compared to 2019 demand and trends from 2015 to 2019. The decline in commercial use was offset by the increase in single-family and multi-family residential water use. This shift is attributed to the Regional Shelter -In-Place/Stay- at-Home Orders. Following the end of the COVID -19 pandemic , water use patterns have gradually returned to pre-pandemic conditions. Residential demand sharply declined from 2020 to 2021, attributed to the lifting of Stay -at-Home Orders, and followed an increasing trend from 2023 to 2025. Commercial demand generally increased to 2019 levels from 2020 to 2025. It is expected that water use trends will continue to follow pre-pandemic trends in the future.
4.3.4 Projected Water Use
Projected water demands are an important factor in predicting water system reliability . These estimates provide a basis to ensure that there is adequate water supply to meet future demands.
All potable water projections in this section are based on methodologies implemented i n the BAWSCA Regional Water Demand and Conservation Study, December 2025 (Demand Study).
The Demand Study included long-term water demand estimates with and without passive/active conservation developed specifically for the City. Only passive conservation is considered for the purpose of projecting future water demand for this UWMP. The full Demand Study is included as Appendix C.
The potable water use projections were developed using a hybrid water demand forecasting framework that integrates econometric modeling with conservation accounting tools . The econometric regression-based model (Econometric Model) links key drivers such as demographic growth, weather conditions, economic factors, and water rates to historical water use in order to estimate a historical rate of use per driver . Th is rate was then used to estimate long -term projected water use. This approach generate d monthly projections of baseline demand for the City that reflects structural drivers of water use. The model considered expected service area population and economic growth as well as passive conservation from plumbing codes and fixture turnover over time. The full description of the Econometric Model and water demand forecasting framework is included in the Demand Study, attached as Appendix C. Projected additional water demand from planned new development and redevelopment within the City’s service area were added to the Demand Study projections.
Projected City potable and recycled (non -potable) water use is summarized by customer classification in Table 4-4. Projected recycled water use is based on anticipated recycled water development. Recycled water is discussed further in Section 6. Because the City is largely built- out, it is expected that water use will continue to rise in future years primarily due to increasing population density. The City provides projected demands to each wholesale water agency (attached as Appendix D ) to help with each wholesaler’s supply reliability assessment and UWMP update.
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Table 4-4: Projected Potable and Non-Potable Water Use by Customer Type (AFY) Customer Type Potable or
Non-Potable1 2030 2035 2040 2045
Single Family Residential Potable 5,323 5,254 5,231 5,209 Multi-Family Residential Potable 6,106 7,232 8,408 9,568 Commercial/Industrial (combined) Potable 4,933 6,241 7,086 7,910 Institutional Potable 315 398 452 505
Irrigation Potable 2,144 2,164 2,180 2,198
Other (Firelines) Potable 133 133 133 133
System Losses2 Potable 1,648 1,863 2,043 2,219
Commercial/Industrial
(combined, recycled water)
Non-Potable 95 119 142 165
Irrigation (recycled water) Non-Potable 637 794 950 1,107 Subtotal Potable3 20,602 23,285 25,533 27,742
Subtotal Non-Potable4 732 913 1,092 1,272
Total 21,334 24,198 26,625 29,014
Notes:
1. Non-potable use includes recycled water and any potable water added to the recycled water system.
2. Projected system losses are 8% of projected potable demand.
3. Projected potable water from the BAWSCA 2025 Demand Study with passive conservation categorized by customer use type and projected additional demand from planned new development and redevelopment within the City’s service area.
4. Projected non-potable use is described in Section 6.
5. Water use within the City’s service area.
4.4 Future Water Savings
Future water use estimates were based on Demand Study projections with passive conservation.
Passive conservation considers any codes or standards that could affect future water use . The model used for the Demand Study projections incorporated passive conservation savings from plumbing codes, which is based on Federal and State legislated efficiency standards (Energy Policy Act of 1992, CALGreen Building Code, and Title 20). These standards govern the available type of fixtures and appliances such as toilets, showers, and washers, which in turn are expected to reduce water usage. Projected passive water conservation savings as outlined in the Demand Study are shown in Table 4-5. Passive conservation is expected to increase in the future due to fixture and appliance replacement over time.
Table 4-5: Projected Passive Water Conservation Savings Conservation 2030 2035 2040 2045
Passive Conservation Savings 358 616 831 1,008
Note:
1. Data from the 2025 BAWSCA Demand Study.
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4.5 Low-Income Housing Water Use Projection
Section 10631.1(a) of the California Water Code requires that water use projections specifically identify the projected water use for lower-income single-family and multi-family residential homes.
As stated in Section 3, lower-income residents are defined as households at 80% of the Area Median Income. The City records the annual number of low- to moderate-income units but does not track the difference between single -family and multi -family homes . For this reason, this section r eports total residential ( single-family and multi -family) demand for low -income units .
These demands are already included in Table 4-4 (see Table 4-6).
Table 4-6: Inclusion in Water Use Projections
Parameter Response
Are future water savings included in projections? Yes
If “yes” to above, state the section or page number where citations of the codes, ordinances, etc. utilized in projections are found. Section 4.4 Are lower income residential demands included in projections? Yes The City has 1,828 low-income units and 770 moderate-income units as of December 31, 2025.
The City projects that there will be an additional 761 low-income units and 75 moderate-income units by 2030. City projections do not go beyond 2030 thus it is assumed that the number of units will remain the same beyond 2030.
Projected low-income water use is based on the number of units, the average household size within the City, and the projected water use factors. Table 4-7 provides the water use projections for low-income households within the City service area.
Table 4-7: Low-Income Estimated Current and Projected Water Use (AFY) Parameter 2025 2030 2035 2040 2045
Low-Income Units 1,828 2,589 2,589 2,589 2,589
Low-Income Residential Water Use (AF) 558 790 790 790 790 Notes:
1. Average Household Size of 2. 59 determined from the 2025 Department of Finance E -5 Population and Housing Estimates for Cities.
2. Projected water use factors are based on 2025 per capita water use ( 105 gallons per capita per day [gpcd]) and assumed to be constant.
4.6 Climate Change Considerations
As described in Section 3 , global climate change has a significant effect on water supply reliability. One of the risks of climate change is the potential for longer and deeper droughts .
Although the City addresses ways to ensure reliability in the event of a drought in its WSCP, it is also important to incorporate climate change impacts in water use projections.
Future water use estimates in this UWMP were determined from Demand Study projections, which account for potential effects of climate change . The Demand Study incorporates climate change assumptions by adjusting future temperatures using projections obtained from CalAdapt’s Local Climate Change Snapshot tool. Background data for the Cal-Adapt tool is sourced from DRAFT
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the Coupled Model Intercomparison Project Phase 5 (CMIP5). The Demand Study incorporated CMIP5 data from two International Panels on Climate Change (IPCC) climate change scenarios, which are referred to as Representative Concentration Pathways (RCP s). These scenarios provide estimates of global temperature based on CO 2 emissions under a variety of mitigation conditions.
Modeled temperatures from the CalAdapt CMIP5 RCP 4.5 and RCP 8.5 datasets for Santa Clara County estimate an annual mean temperature increase of 1. 25 degrees Fahrenheit to 2.05 degrees Fahrenheit for the 2020-2050 period. This temperature increase was incorporated into all water use projections.
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– BASELINES AND TARGETS
The Water Conservation Bill of 2009 (SBX7-7) required a statewide reduction in urban per capita water use by 20% by the year 2020. To achieve this statewide objective, the California Legislature required each water retail supplier to develop a 2020 water use target based on population to help the State collectively achieve a 20% reduction. Reporting for SBX7 -7 began in the 2010 UWMP with the calculation of the Baseline, the 2015 Interim Target, and the 2020 Target, each in units of gpcd. In the 2015 UWMP, each retail agency was required to demonstrate compliance with its 2015 Interim Target to ensure they were on track to meet the goal of 20% reduction by 2020. In the 2020 UWMP, each retail agency was required to demonstrate compliance with its 2020 Target. The Baseline, 2015 Interim and 2020 Targets, and 2020 Compliance are calculated through completion of the SBX7-7 Verification Form prepared by DWR, submitted as part of the 2020 UWMP and attached as Appendix E.
The City’s 2020 per capita water use was 115 gpcd , well below the 2020 target of 139 gpcd .
Thus, the City achieved compliance with SBX7-7 as presented in the 2020 UWMP.
Table 5-1 presents the final 2020 water use and confirmed compliance with SBX7-7.
Table 5-1: 2020 Compliance with SBX7-7
2020 Target (gpcd) Actual 2020 gpcd Did Supplier Achieve Targeted Reduction for 2020? Y/N
139 115 Y
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SECTION 6 – Water Supply Characterization
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– WATER SUPPLY CHARACTERIZATION
The section presents the City’s past, current, and future water supply for potable and non-potable demand. The City has three sources of potable water supply: purchased surface water from SFPUC, purchased treated surface water from Valley Water, and groundwater from six City - owned and operated wells. Recycled water (non-potable) is supplied by the City’s WPCP. The City also has an additional stand-by well for emergency use and emergency interties to the City of Cupertino, the City of Mountain View, the City of Santa Clara, and Cal Water.
6.1 Purchased Water
Most of the City’s water supply comes from purchased surface water from SFPUC and Valley Water. The City does not use any other surface water for supply. The following section describes each wholesaler in more detail.
6.1.1 SFPUC – Wholesaler (Surface Water)
The City receives surface water from the City and County of San Francisco’s RWS, operated by SFPUC. This supply is predominantly from the Tuolumne River watershed in the Sierra Nevada Mountains, delivered through the Hetch Hetchy aqueduct, but also includes treated water produced by SFPUC from local watersheds and facilities in Alameda and San ta Clara counties.
The Alameda watershed, located in Alameda County, is designed to capture local runoff.
The amount of imported water available to SFPUC’s retail and wholesale customers is constrained by hydrology, physical facilities, and the institutional parameters that allocate the water supply of the Tuolumne River. Due to these constraints, SFPUC is dependent on reservoir storage to ensure ongoing water supply.
The business relationship between the SFPUC and its wholesale customers is largely defined by the “Water Supply Agreement between the City and County of San Francisco and Wholesale Customers in Alameda County, San Mateo County and Santa Clara County” (WSA) , effective since July 2009. This 25-year WSA replaced the Settlement Agreement and Master Water Sales Contract that expired in June 2009. The WSA addresses the rate-making methodology used by the SFPUC in setting wholesale water rates for its customers in addition to addressing water supply and water shortages for the RWS. The WSA, as amended and restated in 2025, describes the current contractual relationship between the SFPUC and the City.
The WSA is supplemented by an individual Water Supply Contract between SFPUC and each individual retailer, also active since July 2009. These contracts expire in 25 years. The City has an Individual Supply Guarantee (ISG) of 12.58 MGD (approximately 14,100 AFY). Although the WSA and accompanying Water Supply Contract expire in 2034, the ISG (which quantifies San Francisco’s obligation to supply water to its individual wholesale customers) sur passes their expiration and continues indefinitely . The City’s contract also includes a minimum purchase amount of 7.412 MGD (8,308 AFY), which Sunnyvale agrees to buy, regardless of whether sales drop below this level.
The WSA provides for a 184 MGD (expressed on an annual average basis) Supply Assurance to the SFPUC’s wholesale customers. This Assurance is subject to reduction, to the extent and for the period made necessary by reason of water shortage, due to drought, emergencies, or by DRAFT
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scheduled RWS maintenance activities. The WSA does not guarantee that San Francisco will meet peak daily or hourly demands of SFPUC’s wholesale customers when their annual usage exceeds the Supply Assurance. The SFPUC’s wholesale customers have agreed to the allocation of the 184 MGD Supply Assurance among themselves, with each entity’s share of the Supply Assurance set forth on Attachment C to the WSA.
6.1.2 Valley Water – Wholesaler (Surface Water)
Valley Water supplies the City of Sunnyvale with treated surface water through an entitlement of imported water that is Delta -conveyed from the Central Valley Project (CVP) and State Water Project (SWP), as well as surface water from local reservoirs. The City has a 70-year contractual agreement with Valley Water, effective 1981 to 2051.
Valley Water ’s imported water is conveyed through the Sacramento -San Joaquin Delta and pumped and delivered to the county through three main pipelines: the South Bay Aqueduct, which carries water from the SWP, and the Santa Clara Conduit and Pacheco Conduit, which convey water from the Federal CVP. More than 70% of this supply is delivered to treatment plants, about 15% is diverted upstream by the SFPUC and delivered to cities in northern Santa Clara County, and almost 15% is used for recharge . Any excess Delta -conveyed supplies are stored in the Semitropic Groundwater Bank in San Joaquin Valley for later use, such as withdrawal during dry periods. Valley Water can also store imported water supplies locally in the Anderson and Calero Reservoirs; however, the Anderson Reservoir is currently drained down due to seismic concerns.
Valley Water is working on rebuilding the dam, with completion expected by the end of 2033 (2050 WSMP, 2025).
Local runoff is captured in local reservoirs for recharge into the groundwater basin or treatment at one of Valley Water’s three water treatment plants. The total storage capacity of the ten Valley Water operated reservoirs in Santa Clara County is approximately 166,000 AF, however, several reservoirs are operating at restricted capacity due to seismic stability concerns. Local water captured in local reservoirs and natural groundwater recharge provides up to 30% of Santa Clara County’s water supply . Reservoir operations are coordinated with imported Bay -Delta water received from the SWP and the CVP.
Valley Water has a contract for 100,000 AFY from the SWP and 152,500 AFY from the CVP .
However, the actual amount of water delivered is typically less than these contractual amounts and depends on hydrology, conveyance limitations, and environmental regulations. Valley Water expects average allocations of Delta -conveyed water to generally decline over time due to impacts of climate change, potential environmental regulations affecting the Sacramento–San Joaquin Delta, and State mandates to reduce reliance on the Delta (2050 WSMP, 20 25).
However, over the years, Valley Water has attempted to sustain overall existing supplies by participating in projects that would offset the predicted decline of Delta-conveyed imported water supplies. In October 2019, Valley Water voted to support the Delta Conveyance Project, which is a proposed plan to improve the infrastructure that conveys water through the Sacramento-San Joaquin Delta. This plan would potentially provide on average 14,000 AFY of imported water supply benefits to Valley Water (2050 WSMP, 2025).
Valley Water has also been evaluating water reuse opportunities, including potable reuse, as a reliable, locally controlled s upply that can mitigate drought risks and further diversify its water supply portfolio. In October 2024, the State enacted the Direct Potable Reuse (DPR) regulations, enabling water supply agencies to pursue a new and more flexible approach to potable reuse.
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Valley Water aims to develop 24,000 AFY of potable reuse by 2035, with a long -term vision of expanding water reuse in the county to up to 32,000 AFY by 2050.
Valley Water’s conjunctive management of groundwater and surface water makes it infeasible to directly quantify or demonstrate reduced Delta reliance at a retailer level. However, Valley Water, with the support of all retailers including the City, has made significant investments in demand management and local supplies to reduce Santa Clara County’s reliance on the Delta. Additional information on Valley Water’s reduced reliance on the Delta is provided in Appendix H of Valley Water’s 2025 UWMP.
6.2 Groundwater
The City of Sunnyvale has six active wells and one well on stand -by for emergencies .
Groundwater makes up a small percentage of the City’s total water supply and is used to supplement imported SFPUC and Valley Water supply.
Valley Water manages the groundwater basin and provides county -wide groundwater and conservation planning assistance. Local groundwater supplies represent up to half of the county’s water supply during normal years and are crucial to the region’s future water supply reliability .
Valley Water uses conjunctive use management, a practice by which the groundwater basin is pumped more in drier years and then replenished (or recharged) during wet and average years , to ensure the sustainability of groundwater ba sins. Groundwater is replenished naturally from rainfall and augmented by Valley Water-operated recharge. Conjunctive use helps to protect the groundwater basin from overdraft, land subsidence, and saltwater intrusion, and provides critical groundwater storage reserves.
Within Santa Clara County, Valley Water manages two groundwater subbasins that transmit, filter, and store water: the Santa Clara Subbasin (DWR Subbasin 2 -9.02) and the Llagas Subbasin (DWR Subbasin 3-3.01). The Santa Clara Subbasin is part of the Santa Clara Valley Basin. For water supply planning purposes, Valley Water frequently splits the Santa Clara Subbasin into two subareas for water, the Santa Clara Plain and the Coyote Valley . These two subareas are in separate groundwater charge zones and have different groundwater management challenges and opportunities. The City’s groundwater is supplied by the Santa Clara Plain subarea of the Santa Clara subbasin. A general discussion of this subarea is provided below.
6.2.1 Basin Description
The Santa Clara Plain is part of the Santa Clara Subbasin, located in a structural trough that is bounded by the Santa Cruz Mountains to the west and the Diablo Range to the east. The Plain, which is approximately 22 miles long, narrows from a width of 15 miles near the county’s northern boundary to about half a mile wide at the Coyote Narrows, where the two ranges nearly converge.
The Santa Clara Plain covers a surface area of approximately 280 square miles, which is approximately 17 square miles smaller than the Santa Clara Subbasin. This is because the Santa Clara Plain does not include the Coyote Valley portion of the Santa Clara Subbasin . Although hydraulically connected, Valley Water refers to the Coyote Valley separately since it is in a different groundwater charge zone and has fewer water supply options than the Santa Clara Plain.
Figure 6-1 illustrates the groundwater basin in relationship to the City’s groundwater wells.
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Attachment 1
!(
!(!(!( !(
!(!(
LEGEND
Bedrock
Coyote Valley Unconfined
Llagas Confined
Llagas Unconfined
Santa Clara Plain Confined
Santa Clara Plain Unconfined
Santa Clara County Boundary
!( Sunnyvale Wells Confined
!( Sunnyvale Wells Unconfined
FIGURE 6-1
CITY OF SUNNYVALE
URBAN WATER MANAGEMENT PLAN
SANTA CLARA VALLEY BASIN
N
_
0 17,500 35,000
1 IN = 35,000 FT
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These subbasins contain young alluvial fill formation and the older Santa Clara Formation. Both formations are similar in character and consist of gravel, sandy gravel, gravel and clay, sand, and silt and clay. The coarser materials are usually deposited along the elevated lateral edges of the subbasins, while the flat subbasin interiors are predominantly thick silt and clay sections inter - bedded with smaller beds of clean sand and gravel.
Valley Water manages the groundwater supply in Santa Clara County and works with various water retailers in the area to prevent subsidence and overdraft of the basin . The Santa Clara Valley Basin is currently not adjudicated and has not been identified as critically overdrafted by DWR. The Santa Clara Subbasin is designated by the DWR as a high priority subbasin based on a variety of factors identified in statue such as population, irrigated acreage, and the number of wells (Water Code Section 10933(b)) . Basin Prioritization is based on the Sustainable Groundwater Management Act (SGMA) Basin Prioritization program, updated in 2019 . SGMA requires high -priority basins to develop Groundwater Sustainability Agencies (GSAs) and Groundwater Sustainability Plans (GSPs) to manage groundwater for long-term sustainability.
6.2.2 Historical Groundwater Pumping
Valley Water conducts continuous operational planning to balance water supply and demand, protect groundwater reserves, and maintain sufficient carryover storage. The annual operations planning process begins each fall, when imported and local supplies are estimated and operations scenarios are developed for the following year under varying hydrologic projections. Typically by late spring, when the quantity of imported water available to Valley Water by contract and the local water yield can be estimated with more certainty, Valley Water refines the projections and modifies its groundwater management strategy . As the water year progresses and more information becomes available, the operations plans are revised accordingly to optimize local water supply reliability . A copy of the 2021 Santa Clara Valley Water District Groundwater Management Plan (GMP) is included as Appendix F.
Groundwater is extracted by way of wells, either owned or operated by area retailers or private property owners . The allowable withdrawal of groundwater by the City depends on multiple factors, including withdrawals by other water agencies, the quantity of water recharged, and carry- over storage from the previous year . According to Valley Water’s 2024 Annual Groundwater Report, the City accounts for less than 1% of the total groundwater pumping for the Santa Clara Plain subbasin designated as North County (Zone W-2).
The City has six active wells that can produce up to 8,000 AF annually. However, the City seldom uses these wells since water demand can be adequately met with purchased treated water from SFPUC and Valley Water. The City has on average pumped about 138 AF annually to prevent stagnation and keep the wells active for sampling. The City plans to continue operating the wells in this manner. Table 6-1 shows historic metered groundwater pumping data for the City from 2021 to 2025.
Table 6-1: Past and Current Groundwater Volume Pumped (AFY) Groundwater Type Basin Name 2021 2022 2023 2024 2025
Alluvial Basin Santa Clara Plain Subarea 126 113 138 158 157 DRAFT
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2025 Urban Water Management Plan
SECTION 6 – Water Supply Characterization
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6.3 Stormwater
The City owns and operates approximately 150 miles of storm drains and two pump stations that collect runoff and discharge to creeks and sloughs . Stormwater is conveyed through the City’s storm sewer system, separate from the sanitary sewer system, to four waterways that flow to San Francisco Bay: Sunnyvale West Channel, Sunnyvale East Channel, Stevens Creek, and Calabazas Creek. The City does not currently utilize stormwater to meet local water supply demands. However, the City is subject to regulations that aim to improve the quality of stormwater runoff and manage stormwater flows.
The 2014 California Water Action Plan led to the State Water Board’s “Strategy to Optimize Resource Management of Stormwater” (STORMS), which was created to promote stormwater as a valuable resource and provide support and funding for collaborative watershed -level storm water management and pollution prevention . STORMS is one of many Federal and State initiatives that have influenced new stormwater management requirements in Bay Area municipal stormwater National Pollutant Discharge Elimination System (NPDES) permits.
Since 2016, the City is subject to the requirements of the Municipal Regional Stormwater NPDES Permit (MRP) for Phase I municipalities and agencies in the San Francisco Bay area. The current MRP (MRP 3, Orders R2-2022-0018 and R2-2023-0019) includes new requirements and targets concerning reducing trash loads from stormwater, improving water quality of discharge, implementing green stormwater infrastructure (GSI), and utilizing low impact development (LID) site design. GSI attempts to mimic natural watershed processes by using plants and soil systems to capture stormwater, therefore reducing stormwater runoff and pollutant load discharged into receiving surface waters. LID uses site design approaches and management practices for new development or redevelopment to help decentralize stormwater management and maintain hydrologically functional landscapes. Examples of LID site design include reducing or disconnecting impervious surfaces, implementing bioretention or other small-scale stormwater controls, and preserving natural area and open space . The City’s Green Stormwater Infrastructure Plan, adopted September 2019, provides a framework to gradually transform the City’s traditional storm drainage infrastructure to GSI.
The City is a member of the Santa Clara Valley Urban Runoff Pollution Prevention Program (SCVURPPP), which is an association of thirteen cities and towns in the Santa Clara Valley, the County of Santa Clara, and Valley Water that collaborate on stormwater regulatory activities and compliance. This program aims to improve the water quality of south San Francisco Bay and the streams of Santa Clara County by reducing nonpoint source pollution in storm water runoff and other surface flows.
6.4 Wastewater and Recycled Water
The City treats its wastewater and produces recycled water at the WPCP located at 1444 Borregas Avenue. A wastewater reclamation program was developed in 1991 when the City first identified short-term goals of recycling 20-30% of wastewater to produce high-quality effluent from the Plant. Today the City has a developed recycled water program , in partnership with Valley Water, which today serves parks, golf courses and the landscaping needs of diverse industries .
The long-term goal of the City is to maximize the use of recycled water which has the potential to reach 2.1 MGD for non-potable uses.
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6.4.1 Wastewater Collection, Treatment, and Disposal
The WPCP has a permitted dry weather flow capacity of 29.5 MGD with a 40 MGD peak wet weather flow capacity , though current flows average approximately 15 MGD. The amount of influent wastewater handled by the Plant varies with the time of day and seasonal changes in demand. Wastewater is collected from the sanitary sewer system, which consists of more than 380 miles of gravity fed pipes that converge at the Plant. Collected wastewater is then treated to tertiary standards before it is either distributed back to the City for recycled water uses or discharged to the Lower South Ba y subembayment of the San Francisco Bay via the Moffett Channel and Guadalupe Slough. The overall treatment consists of the following processes:
• Primary Treatment (Sedimentation)
• Secondary Treatment (Oxidation)
• Tertiary Treatment (Filtration and Disinfection)
These processes provide treatment to a level that will meet NPDES discharge requirements.
Most of the treated water is discharged to the San Francisco Bay via the Moffett Channel and Guadalupe Slough. Approximately 10% of the Plant flow is treated to a higher level to meet the necessary recycled water quality and delivered to customers for non -potable uses, primarily irrigation.
Sunnyvale has experienced a slight decrease in Plant influent over the past five years but anticipates a conservative influent flow of 15 MGD over the next 25 years. Table 6-2 and Table 6-3 summarize the City’s collected, treated, and discharged wastewater in 2025.
6.4.2 Future Wastewater Improvement Projects
The WPCP was originally constructed in 1956 and is one of the oldest wastewater treatment facilities on the West Coast. Although the Plant continues to provide reliable wastewater treatment, several of the Plant’s existing facilities are nearing the end of their useful life. The City created the Cleanwater Program to upgrade the Plant through a series of projects that will rehabilitate existing Plant facilities and construct new facilities, ensuring future wastewater treatment reliability. These projects include upgrades to the secondary and tertiary treatment facilities, construction of new biosolids handling facilities, and construction of new administration and maintenance buildings at the Plant. Several improvements are currently in design phase and some have started construction. The projects associated with the Cleanwater Program are outlined in more detail on the Sunnyvale Cleanwater website (https://www.sunnyvalecleanwater.com) and in the WPCP Master Plan (2014-2016). The City is currently preparing a WPCP Master Plan Update , anticipated to be completed November 2026, that will provide a more detailed roadmap for the next phase of the Cleanwater Program.
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Table 6-2: Wastewater Collected within Service Area in 2025 (AFY) Wastewater Collection Recipient of Collected Wastewater Name of Wastewater
Collection Agency
Wastewater Volume
Metered or Estimated?
Volume of Wastewater
Collected from UWMP Service
Area 2025
Name of Wastewater Treatment
Plant and Place ID Number
Is WWTP Located
within UWMP Area?
City of Sunnyvale Metered 15,817 Sunnyvale WPCP, Place ID 259507 Yes
Table 6-3: Wastewater Treatment and Discharge Within Service Area in 2025 Wastewater
Treatment
Plant Name
and Place ID
Number
Does This
Plant Treat
Wastewater
Generated
Outside the
Service
Area?1
Treatment
Level
Total 2025
Volume of
Water
Treated (AF)
2025 Outcomes of Treated Water
Water
Recycled
Within Service
Area (AF)2
Water
Recycled
Outside of
Service Area
(AF)2,3
Effluent
Discharge
that is not a
Permitted
Recycled
Water Use4
Required
Discharge for
Instream
Flow5
Delivered to
Another Entity
for Additional
Treatment
Sunnyvale
WPCP,
Place ID 259507
Yes Tertiary 15,817 641 494 13,663 - 0
Notes:
1. The City treats wastewater for the small pockets of Cal Water customers within City limits as well as a pocket of customers in Cupertino.
2. Total usage includes recycled water and potable water delivered through the recycled water system. Recycled water produced at the WPCP accounts for approximately 8% of total usage. Usage does not include disinfected secondary recycled water diverted for WPCP process prior to recycled water distribution system, which is not counted towards Statewide Recycled Water volume.
3. Services outside City limits include Moffett Field and the Apple® Campus 2.
4. Effluent flows do not include No. 3 water (non -potable Plant service water used internally for operations) or backwash water. No. 3 water is used in several plant processes, including polymer dilution, washdown water, Synagro dewatering, and other miscellaneous purposes.
5. The City does not currently have instream flow requirements.
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2025 Urban Water Management Plan
SECTION 6 – Water Supply Characterization
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6.4.3 Recycled Water System Description
The City’s current recycled water system consists of the Recycled Water Pump Station located at the WPCP, the Sunnyvale Golf Course pump station, the San Lucar Tank and Pump Station, the Wolfe Road Pump Station (WRPS), and approximately 22 miles of recycled water pipelines ranging in diameter from 6- to 36-inches. The WRPS was completed in 2018 as part of the Wolfe Road Pipeline Extension Project, which added approximately 13,000 feet of pipeline to extend the recycled water system along Wolfe Road, reachi ng the Apple® Campus 2. Both the WRPS and the pipeline extension are owned by Valley Water and maintained by the City’s Water and Sewer Services Division. In 2018, the City completed a Capital Improvement Project to facilitate parallel production of recycled water and NPDES discharge, thereby providing enhanced production and delivery reliability.
The use of recycled water provides substantial benefits to the environment and a variety of communities. The following examples outline how the City’s use of recycled water positively impacts different groups:
• Potable water users benefit from the decreased reliance on imported supply. • All Sunnyvale residents benefit from securing a long -term adequate water supply to sustain economic growth and ensure public health.
• Recycled water users benefit by avoiding strict conservation requirements and water use restrictions during times of drought, and by paying less than the cost of potable water. • All water users benefit from bringing in another water source to augment supplies. • Area wetlands benefit from reduced freshwater discharges into the saline wetlands.
6.4.4 Potential, Current, and Projected Recycled Water Use The City supplements their recycled water system with potable water additions at the Plant or the San Lucar Pump Station. This is used to offset the difference between recycled water production and demand and to improve water quality for irrigation of sensitive plants . The City’s recycled water system supplies an average of 1.0 MGD for over 100 services within the City limits as well as Moffett Field and the Apple® Campus 2 . Current and projected recycled water usage is categorized by reuse application, or beneficial use type, and reported in Table 6-4. Projected recycled water usage was estimated based on projected phased expansion described in the City’s 2024 Recycled Water Master Plan Update (RWMPU), discussed further in Section 6.4.5.
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City of Sunnyvale
2025 Urban Water Management Plan
SECTION 6 – Water Supply Characterization
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Table 6-4: Current/Projected Recycled Water Direct Beneficial Uses within Service Area Beneficial
Use Type
Potable
or Non-
Potable
General
Description of
2025 Uses
20251 2030 2035 2040 2045
Volume of
Recycled Water
Available for Use2
Landscape
Irrigation
(excl. golf
courses)
Non-
Potable
Parks, Green
Belts, Schools,
etc.
480 522 678 835 992 90
Golf Course
Irrigation
Non-
Potable
Fairway
Irrigation 71 115 115 115 115 0
Commercial
Use
Non-
Potable Dual Plumbing 76 73 91 109 127 0
Industrial Non-
Potable Cooling 14 22 27 33 38 0
Total Non-Potable 641 732 912 1,092 1,272 90
Notes:
1. Although 90 AF of recycled water was produced at the WPCP, approximately 1,045 AF of purchased potable water from SFPUC was added to the recycled water distribution system, making the total recycled water demand 1,135 AF. Approximately 641 AF was distributed within City limits , with the remaining 494 AF distributed to services outside City limits (Moffett Field and the Apple® Campus 2).
2. The City has historically produced significantly more than 90 AF of recycled water; however, production was limited in 2025 due to challenges in meeting Title 22 turbidity requirements . The City is currently constructing a new secondary treatment system at the WPCP that is expected to produce effluent with significantly lower turbidity compared to the existing treatment process.
3. Units in AFY.
Table 6-5 compares the actual 2025 uses of recycled water to the projected uses in the 2020 UWMP. Total recycled water use in 2025 decreased from 2020 levels by app roximately 72 AF and was approximately 255 AF less than projected in 2020. The greatest difference occurred in projected golf course irrigation demand, which is 222 AF lower than the amount projected in 2020.
One potential reason for this difference is that the 2025 value reflects recycled water use within City limits and excludes Moffett Field, which had a total recycled water use of 214 AF in 2025.
Additionally, the City has an upcoming recycled water project, described further in Section 6.4.5, that will connect Sunken Gardens Golf Course to the recycled water system, potentially increasing recycled water use for golf course irrigation within City limits in the near future.
Table 6-5: 2020 UWMP Recycled Water Use Projection Compared to 2025 Actual (AFY) Use Type 2020 Projection for 2025 2025 Actual Use
Landscape Irrigation (excl. golf courses) 486 480
Golf Course Irrigation 293 71
Commercial 90 76
Industrial 27 14
Total 896 641
Note: Recycled water use within service area.
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2025 Urban Water Management Plan
SECTION 6 – Water Supply Characterization
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6.4.5 Projected Future Uses of Recycled Water
The City conducted a Feasibility Study in 2013 to identify potential expansions of the recycled water system. In July 2024, the RWMPU was completed to provide a comprehensive update to the Feasibility Study. The RWMPU reviews existing demands and infrastructure and evaluates potential customer demands and proposed infrastructure through desktop analyses and hydraulic modeling.
Estimates of potential recycled water demand for sites within the City’s service area were determined using City water billing records. Based on these estimates, recycled water pipeline alignments were developed to extend the existing system to major potential customers in a cost- effective manner. Additional a lignments were identified to provide opportunities for system looping to improve reliability. Multiple alignments and expansion alternatives were evaluated using hydraulic modeling, with alignments grouped to accommodate a phased approach to construction. The key findings detailed in the RWMPU are summarized into the following potential phases for future expansion:
• Infill Connections: This phase would consist of connecting to cu stomers that have been identified along existing recycled water pipelines and require only retrofits of existing sites to receive recycled water. These are the most cost -effective connections and provide the highest opportunity for near-term recycled water expansion. Most of this potential is located within the Moffett Park Specific Plan area.
• Maximize Existing System and Facility Capacity: This phase includes expanding the existing system with pipeline alignments that branch from the existing system in the northern area of the City, identified in the RWMPU as the lower pressure zone, to maximize the existing recycled water system capacity. These alignments could be constructed without any storage or pumping capacity improvements.
• System Looping and Storage and Pumping Upgrades : This phase includes pipeline alignments to loop the existing recycled water system for reliability and connect to a future storage tank and pump station site to provide opportunities for further expansion in the south side of the City.
• Full Buildout with System and Facility Upgrades: This phase assumes full buildout of the City’s recycled water system and full expansion in the southern area of the Cit y, identified in the RWMPU as the upper pressure zone . Th e additional branching and looping pipeline alignments identified in this alternative require storage and pumping capacity improvements to meet the total potential recycled water demand.
Figure 6-2 illustrates the existing recycled water distribution system and the potential expanded recycled water system based on the RWMPU.
As part of the FY 2025 -26 Adopted Budget, the City has approved the construction of approximately 2,370 feet of recycled water pipeline as part of CIP Project #837450. This project serves to expand the distribution system in two areas: 1) 1,400 feet to connect existing pipelines and remove dead ends in the existing syste m to increase reliability, and 2) 970 feet extending from the existing system to serve the Sunken Gardens Golf Course. The estimated demand to be served at the golf course is 44 AFY. Table 6-6 lists the recycled water projects planned for implementation by the City to encourage and expand future recycled water use.
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Attachment 1
Villa St
W Mid dlefiel
d Rd
Shoreline Golf
Links
M ount ain
V iew
Gra
nger Ave
Rancho San
Antonio
E Ar qu es A veW W ash ing ton Ave
E E
velyn Ave
E Evelyn
Ave
Kife r Rd
Fairch
ild Dr
N
Mary
Ave
Ca
ldero
n
Ave
W Evelyn Av
e
Manila Dr
N Borregas Ave
N W
ol
fe R
d
Tasman Dr
Gra
nt Rd
Moffett B
lvd
Cen tral Exp y
W El Cam
ino Real
La
wre
nce
Expy
W V
alley Fwy
Sunnyvale Golf
Course
Sunnyvale
Baylands
Moffett Federal
Airfield
South Shore
Port
S unnyvale
G2
Gra
pe
Ave
W Remington DrS Bernardo
Ave
Ir is Ave
Henderson Ave
The Dalles Ave
Reed AveLevin Ave
Oak Ave
Popla
rAve
Ca rlisle Way
Fa
llen
Le
af
Ln
B
elle
ville
W
ay
Crest
on
Dr
N Blaney
Av
e
N Stelling Rd
Grant Rd
Sunnyvale Saratoga Rd
W Fremont Ave
E Homestead Rd
N De Anza Blvd
EEl
Cam
ino R
eal
Lawre
nce Expy
Foothill
Expy
W
Valley F
wy
Calabazas Creek
SanTomas
Aquino
Creek
Kifer Rd
Scott Blvd
Central Expy
Santa Clara Golf
and Tennis Club
Alviso
Nobil
i Ave
War burton
Ave
Ame
thy
st Dr
Benton St
Po
meroy Av
e
Woo
dh
ams
Rd
Monr oe St
Sa
n To
mas Expy
101
85 237
82 280
FIGURE 6-2
CITY OF SUNNYVALE
URBAN W
ATER MANAGEMENT PLAN
POTENTIAL RECYCLED WATER SYSTEM EXPANSION
LEGEND
EXISTING RW PIPELINE
EXISTING FACILITY
POTENTIAL STORAGE AND PUMPING SITE
INFILL CONNECTIONS
EXISTING SYSTEM BRANCHING (LOWER)
LOWER PRESSURE ZONE LOOP
FUTURE EXPANSION
CITY LIMITS
0 2,250 4,500
1 IN = 4,500 FT
N
_
SUNNYVALE GOLF COURSE
PUMP STA
TION
WPCP
SAN LUCAR TANK AND
PUMP STA
TION AND WRPS
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Table 6-6: Methods to Encourage Future Recycled Water Use (AFY) Name of Action Description
Planned
Implementation
Year
Expected
Increase in
Recycled Water
Use (AF)
Recycled Water Pipeline
Expansion (CIP #837450)
Installation of approximately 970 lineal feet of
6" RW pipeline will allow for the irrigation of
the existing Sunken Gardens Golf Course
2027/2028 44
Total 44
Valley Water, in collaboration with the City and other local stakeholders, developed a Countywide Water Reuse Master Plan (CWRMP) in June 2021. This plan outlines strategies to integrate and expand recycled and purified water throughout Santa Clara County. The plan includes options to build purified water pipelines or extend recycled water pipelines through Sunnyvale, potentially creating future opportunities to expand the City’s recycled water system.
6.4.6 Recycled Water Optimization and Incentives
Division 7, Chapter 7 of the Water Code, known as the Water Recycling Law, provides a legal basis for mandating the use of recycled water . The law states that the use of potable water for non-potable purposes (including irrigation) constitutes a waste or unreasonable use of water if recycled water of suitable quality is available at reasonable cost . Based on State law, some jurisdictions have implemented “mandatory use” policies through local ordinance.
The City currently has several incentives to encourage the use of recycled water, including:
• Reduced cost: Recycled water is priced at 90% of the prevailing, first-tier potable water rate.
Additionally, the monthly service fee is cheaper for recycled water than for potable water. The City intends to continue th ese financial incentive s in the foreseeable future . With few exceptions, the pricing policy has been successful in encouraging prospective users to convert to use of recycled water in areas where it is available. • Dual plumbing: The City is seeing growth through redevelopment, bringing opportunity to install dual plumbed systems in commercial buildings under new construction. Dual plumbed buildings use recycled water for toilets and urinals, cooling towers, and any other identified non-potable water use.
• Permit process enhancement: The City provides fast-tracked permit processing for recycled water applications.
• Public outreach and marketing: The active public education process increases awareness on recycled water.
• Retrofit assistance: The City offers retrofit assistance for dedicated irrigation meters.
These incentives are planned to be implemented on an ongoing basis. Environmental changes such as a re-occurrence of drought conditions and future regulatory changes are also expected to cause further interest in recycled water. In 2023, California State Legislature enacted AB 1572, which prohibits the use of potable water to irrigate non -functional turf on certain properties beginning in 2027 . This policy change may encourage both existing customers and new developments to use recycled water to irrigate non-functional turf areas.
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6.4.7 Recycled Water Streamflow Augmentation and Groundwater Recharge Non-irrigation uses such as stream flow augmentation and groundwater recharge represent long- term options and solutions that could potentially accommodate large amounts of recycled water flow. The City relies on Valley Water activities to maintain sustainable supplies, including managed groundwater recharge and in -lieu groundwater recharge (e.g., treated surface water deliveries, demand management programs, and SFPUC supply).
6.4.8 Recycled Water Coordination
The City collaborated with the Valley Water, Cal Water, DWR, and Apple® to complete the Wolfe Road Pipeline Extension Project in 2018.
The City partnered with Valley Water through the Recycled Water Joint Committee (RWJC), which facilitates partnership opportunities such as expanding recycled water beyond City borders and exploring the potential of advanced treatment of recycled water for potable reuse. The City also collaborated with Valley Water on the 2021 CWRMP.
The SWRCB Division of Drinking Water (DDW) and the SWRCB regulate the production and use of recycled water in the State of California . The City complies with Water Reclamation Requirements for Recycled Water Use (Order WQ 2016-0068-DDW, General Order), adopted by the SWRCB on June 7, 2016. The General Order outlines standard conditions concerning recycled water. Recycled water provided by the City meets the requirements of California Code of Regulations Title 22 as disinfected tertiary treated water.
6.5 Desalinated Water
Both SFPUC and Valley Water are working together with the East Bay Municipal Utilities District, Contra Costa Water District, and the Zone 7 Water Agency as the Bay Area Regional Desalination Project (BARDP). BARDP was created in 2002 and originally proposed a 120 MGD desalination facility that would remove salt from seawater or other brackish water sources . This facility was intended to be used during major facility outages and emergencies. Over the years the concept has evolved to consist of locating one 10-20 MGD desalination facility in eastern Contra Costa County. Desalination would provide potential potable water supply for municipal and industrial use. The goals of desalination are to:
• Increase supply reliability by providing water supply when needed from a regional facility. • Provide additional source of water during emergencies such as earthquakes or levee failures. • Provide a supplemental water supply source during extended droughts. • Allow other major facilities, such as treatment plants, water pipelines, and pump stations, to be taken out of service for maintenance or repairs.
In 2023, Valley Water completed a preliminary environmental feasibility study for the development of a desalination project in Santa Clara County (Desalination Environmental Feasibility and Planning Study , https://assets.valleywater.org/files/Desal Environmental Study_Final_July 2023b.pdf). The study represents the first phase in evaluating a potential desalination project in the county and indicates that a desalination facility in the county may be feasible provided certain DRAFT
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environmental issues are add ressed. The dates for design completion, permitting, and construction are still to be determined . Additional details regarding desalinated water opportunities can be found in the SFPUC and Valley Water UWMPs.
6.6 Water Exchanges and Transfers
The City is currently connected to the City of Cupertino, the City of Mountain View, the City of Santa Clara , and Cal Water through service connections located within Sunnyvale . These interties are intended for use during emergency situations, as presented in Table 6-7.
Table 6-7: Transfer and Exchange Opportunities
Transfer Agency Transfer or
Exchange
Short Term or
Long Term
Proposed Volume
(AFY)
City of Cupertino Emergency Transfer Short Term 0
City of Mountain View Emergency Transfer Short Term 0
City of Santa Clara Emergency Transfer Short Term 0
California Water Service Company Emergency Transfer Short Term 0 Note:
1. The City is not proposing to transfer or exchange any water other than in the case of emergency.
Most of the regional transfer/exchange opportunities are managed by the wholesalers SFPUC and Valley Water. In general, SFPUC can purchase additional water from the Tuolumne River and those sellers south of the Delta with water rights or entitlements to water diverted from the Delta. Water can also be purchased upstream of the Delta from sellers along the Sacramento, Feather, Yuba, American, and San Joaquin Rivers; and their tributaries.
Valley Water conducts short-term water transfers and exchanges as a part of its routine imported water operations. Although Valley Water considers water exchange and transfers as one of the potential options to secure additional water during critical dry years through long te rm agreements, due to the uncertainties regarding long term costs and ability to make transfers in critical dry years, Valley Water did not include water transfers and exchanges in its 2025 UWMP projected water supplies. Instead, they are used as supplemental supply during multi -year droughts to address potential shortages, consistent with Valley Water’s drought management practices.
6.7 Future Water Projects
The City’s water is supplied primarily by the two wholesale providers, Valley Water and SFPUC.
Groundwater is typically used to offset peak daily demands and for emergency purposes such as drought conditions and wholesale water service interruptions . The 20 -year budget includes conceptual funding to reconstruct the Central Well, which has been out of working order since 2007. This well would be used as a backup to Valley Water and SFPUC supply. Preliminary investigation and design are anticipated to commence in FY 2027/28, with construction following in FY 2028/29. This project is not a joint project with other suppliers.
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6.8 Summary of Existing and Planned Sources of Water
As outlined in this section, the City’s existing water supply sources are purchased surface water from SFPUC and Valley Water, groundwater, and recycled water. A breakdown of the City’s 2025 water supply sources is provided in Table 6-8 and presented in Figure 6-3.
Table 6-8: 2025 Water Supplies – Actual (AFY)
Water Supply Additional Detail on
Water Supply
Potable or
Non-Potable Actual Volume Total Entitlement
or Safe Yield
Purchased Water1 SFPUC Potable 11,786 14,100
Purchased Water2 Valley Water Potable 7,267 9,700
Groundwater Wells Potable 157 8,000
Recycled Water3 Produced recycled
water Non-Potable 90 -
Subtotal Potable 19,210 31,800
Subtotal Non-Potable 90 -
Total 19,300 31,800
Notes:
1. Approximately 1,045 AF of purchased potable water was added to the recycled water distribution system.
2. Contractual volumes from Valley Water vary from year to year. Valley Water temporarily suspended deliveries to the City in November 2025 due to the West Pipeline Phase 1 Project. The project includes inspection and repair of segments of the West Pipeline, which carries treated water from the Rinconada WTP to the City.
3. Although 90 AF of recycled water was produced at the WPCP, approximately 1,045 AF of purchased potable water from SFPUC was added to the recycled water distribution system, making the total recycled water demand 1,135 AF. Approximately 641 AF was distributed within City limits, with the remaining 494 AF distributed to services outside City limits (Moffett Field and the Apple® Campus 2).
Figure 6-3: Percentage of Water Supply Sources (2025)
Groundwater Wells
0.8%
Recycled Water
0.5%
SFPUC
61.1%
Valley Water
37.7%
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SECTION 6 – Water Supply Characterization
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Supply projections for the City’s four sources of potable and non -potable water provide a basis for assessing water supply reliability. The breakdown of total supply by source was determined using the City’s contractual agreements with each wholesaler , projected demands provided to each wholesaler, and historical production trends . Current and projected water supply is listed by source in Table 6-9.
Table 6-9: Water Supplies – Projected (AFY)
Water Supply Additional Detail
on Water Supply
Potable or
Non-Potable 2030 2035 2040 2045
Purchased Water1 SFPUC Potable 12,008 12,490 13,389 14,091 Purchased Water2 Valley Water Potable 9,341 11,222 11,928 12,163 Groundwater3 Wells Potable 8,000 8,000 8,000 8,000
Recycled Water Recycled Water Non-Potable 732 912 1,092 1,272 Subtotal Potable 29,349 31,712 33,317 34,254
Subtotal Non-Potable 732 912 1,092 1,272
Total 30,081 32,624 34,409 35,526
Notes:
1. Total available supply from SFPUC is equal to the City’s ISG o f approximately 14,100 AF; however, for planning purposes, the reasonably available volume presented herein reflects the projections provided to SFPUC based on the City’s projected demand and the availability of other supplies.
2. The projections provided herein reflect projections provided to Valley Water based on the City’s projected demand and availability of other supplies. The City can purchase additional available water from Valley Water during non- dry years when water is available.
3. Although the City has on average pumped about 138 AF annually, the total safe yield of groundwater is 8,000 AFY.
As can be seen from the data presented, the City has adequate supply to meet the projected water demand outlined in Section 4 under normal year conditions.
6.9 Energy Intensity
Water Code section 10631.2.(a) details requirements for each Supplier to address the amount of energy used to extract, divert, convey, distribute, treat, and store treated or non -treated water supply, based on readily available information . For the purposes of this UWMP, energy consumption from utility bills was analyzed to determine the quantity of energy used for water management processes.
Monthly PG&E billing data for the City’s six active wells (Hamilton Wells 2 and 3, Serra, Ortega, Westmoor, and Raynor) and the Hamilton Well Pump Station were used to determine metered electric usage for 2025. Since wells and pumps were combined on the utility bills, energy use from all wells and pumps is totaled as a lump sum for all potable water management processes.
Estimated electric usage for 2025, based on available data, is shown in Table 6-10.
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2025 Urban Water Management Plan
SECTION 6 – Water Supply Characterization
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Table 6-10: Energy Usage for Calendar Year 2025
Sum of All Potable Management Processes (Total Utility) Volume of Potable Water Delivered (AF) 18,165
Energy Consumed (kWh) 177,093
Notes:
1. The City does not currently utilize non-consequential hydropower; therefore, this energy source was not included in the table.
2. Energy consumed reflects the sum of available data only.
In 2016, the City and twelve other local communities formed Silicon Valley Clean Energy (SVCE) to provide the region with clean electricity and reduce greenhouse gas emissions. SVCE supplies electricity principally from wind, solar and hydro resources, and is helping communities switch from fossil fuels to clean electricity in buildings and transportation. The City currently purchases clean energy from SVCE.
Energy demands to treat recycled water supplies at the WPCP are supplied in large part by cogeneration. Cogeneration is a process which uses an internal combustion engine to produce heat and electrical power from biogas, or methane, emitted during the treatment process. Biogas produced in the Plant’s anaerobic digesters and the adjacent landfill satisfy most of the Plant’s operational energy demands. The City’s budget includes funds dedicated to replacing existing cogeneration facilities and upgrading un its with newer technologies . As part of the Cleanwater Program, the City is currently working on a Cogeneration Upgrade Design that will replace the Plant’s outdated engines to improve reliability of on -site renewable power production, reduce natural gas usage, and decrease overall air emissions from the Plant. The design completion of the Cogeneration Upgrade is expected in 2027.
In addition to energy from biogas, the City is expanding solar power generation at several municipal facilities. In 2024, the City installed solar panels at the Sunnyvale Materials Recovery and Transfer Station (SMaRT ® Station) that provide renewable power for the onsite processing systems. This reduces operational energy costs for the facility and reduce s greenhouse gas emissions, aligning with the City’s Energy Policy and the goals outlined in the City’s Playbook.
The City’s new City Hall building, completed in 2024, also incorporates on-site solar generation and battery storage to allow the facility to operate using solar power.
6.10 Climate Change Impacts to Supply
The region is subject to growing water supply challenges concerning climate change, including recurring droughts and increased demand from population growth . The City’s potable water is primarily supplied by SFPUC and Valley Water; as such, the City relies on each wholesaler to address the effects of climate change in their long-term planning efforts.
As mentioned in Section 3, the City has considered the effects of climate change on water supply in local projects and plans . The City updated its 2019 Climate Action Playbook in June 2024 (Climate Action Playbook Update and Game Plan 2028 , Playbook). The Playbook’s Strategy 4 (Managing Resources Sustainably) includes a goal (Play 4.2) to ensure the resilience of the City’s water supply in the face of climate change. Methods listed to achieve this goal include reducing the amount of water consumed and promoting water conservation and water reuse, in the form of recycled and purified water . The City will continue to develop specific actions (called “Moves”) every five years to ensure the goal of resilient water supply is achieved.
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Most of the City’s water supply comes from SFPUC and Valley Water. Valley Water released the 2050 Water Supply Master Plan (2050 WSMP , https://fta.valleywater.org/dl/RQWqGqbX3rrk) in 2025, which includes a discussion on the effects of climate change on water supply reliability.
Some of the outlined effects include decreased imported water supplies, increased seasonal irrigation demands, and increased cooling water demand.
SFPUC has been conducting climate change research since 2009. In partnership with The Water Research Foundation , SFPUC developed the Long Term Vulnerability Assessment (LTVA , https://www.sfpuc.gov/about-us/reports/long-term-vulnerability-assessment) of the RWS , which was completed in 2021 and amended in 2024. The LTVA evaluates how climate change could impact the RWS through 2070 by assessing the potential impacts of increases in temperature and changes in precipitation. The LTVA finds that while climate change may exacerbate other external drivers of vulnerability, the RWS remains resilient under a baseline demand of 227 MGD.
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2025 Urban Water Management Plan
SECTION 7 – Water Supply Reliability and Drought Risk Assessment
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– WATER SUPPLY RELIABILITY AND DROUGHT RISK ASSESSMENT
Water service reliability reflects the City’s ability to meet the water needs of its customers under varying conditions. Assessing water service reliability and potential risk is critically important to future City planning and water management . This section evaluates and addresses the City’s long-term reliability of local and regional water supplies under normal conditions, a single dry year, and five consecutive dry years. Supply and demand projections from Section 4 and Section 6 are used for this analysis, along with consideration of foreseeable hydrologic variability, regulatory variability, climate conditions, etc. that may affect supply . This section also includes a Drought Risk Assessment (DRA) to evaluate the City’s risk under a severe drought period lasting for the next five consecutive years.
The City relies on four water supply sources; surface water from SFPUC, treated surface water from Valley Water, groundwater, and recycled water . Surface water from the two wholesalers, SFPUC and Valley Water, provides most of the City’s water supply, averaging about 97% since 2015. City owned- and operated-wells provide less than 1% of water supply, and recycled water makes up the remaining 2%.
7.1 Constraints on Water Sources
In addition to drought, constraints such as water quality, climate change, and changes in regulation can impact water supply . The City relies on their diversification of water supply, continuous work with SFPUC and Valley Water, demand management strategies as discussed in SECTION 9 , and a Water Conservation Plan (included as Appendix G ) to address these constraints.
7.1.1 Water Quality Impacts on Reliability
SFPUC
Surface water supplies available to the RWS include the Tuolumne River and local Bay Area reservoirs. Most of the water supply originates in the upper Tuolumne River watershed high in the Sierra Nevada Mountains, where the watershed is protected from development and pollution.
Water from Hetch Hetchy Reservoir is conveyed to the Bay Area through a system of pipes and tunnels and requires only primary disinfection, ultraviolet light disinfection at the Tesla Treatment Facility, and pH adjustment for corrosion control.
The United States Environmental Protection Agency (USEPA) and SWRCB DDW have approved the use of this drinking water source without filtration. In contrast, water from the SFPUC’s local watersheds requires filtration to meet drinking water quality standards. The SFPUC blends filtered and treated local water with water from Hetch Hetchy Reservoir, and most customers receive this blended supply. The SFPUC continuously monitors and tests both raw and treated water to ensure that water delivered to customers meets or exceeds Federal and State drinking water and public health requirements. The SFPUC expects to continue relying on these high - quality water sources and does not anticipate future degradation of water quality.
Each spring, the SFPUC publishes an annual water quality report (Consumer Confidence Report), available at www.sfpuc.gov/waterqualityreport.
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City of Sunnyvale
2025 Urban Water Management Plan
SECTION 7 – Water Supply Reliability and Drought Risk Assessment
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Valley Water
Valley Water provides treated surface water to local municipalities and private water retailers who deliver the water directly to homes and businesses in Santa Clara County. Valley Water’s surface water is mainly imported from the South Bay Aqueduct, Dyer Reservoir, Lake Del Valle, and San Luis Reservoir, which all draw water from the Sacramento-San Joaquin Delta watershed. Valley Water’s local water sources include Anderson and Calero Reservoirs. Water from imported and local sources is pumped to and tr eated at three water treatment plants located in Santa Clara County. Treatment of surface water is necessary to ensure that the water provided meets or exceeds all Federal and State drinking water standards. Surface water quality programs include treating local and imported surface water for sale to retailers; participating in regional and statewide coalitions to safeguard source water quality protection; and investigating opportunities for water quality improvements through partnership in regional facilities or exchanges.
Valley Water’s source waters are vulnerable to potential contamination from a variety of land use practices, such as agricultural and urban runoff, recreational activities, livestock grazing, and residential and industrial development. The imported sources are also vulnerable to wastewater treatment plant discharges, seawater intrusion, and wildfires in open space areas . In addition, local sources are also vulnerable to potential contamination from commercial stables and historic mining practices. No contaminant associated with any of these activities has been detected in Valley Water’s treated water . The water treatment plants provide multiple barriers for physical removal of contaminants and disinfection of pathogens.
Groundwater
Valley Water monitors groundwater quality to assess current conditions and identify trends or areas of special concern . Wells are monitored for major ions, such as calcium and sodium, nutrients such as nitrate, and trace elements such as iron . Wells are also monitored for man - made contaminants, such as organic solvents . The type and frequency of monitoring depends on the well location, historic and current land use, and the availability of groundwater data in the area. As the groundwater management agency in Santa Clara County, Valley Water has ongoing groundwater protection programs to ensure high water quality and more reliable water supplies .
These programs include water quality monitoring, well permitting, well destruction, wellhead protection, land use and development review, nitrate management (targeted to areas of elevated nitrate in the Coyote Valley and the Llagas Subbasin), saltwater intrusion prevention programs, and providing technical assistance to regulatory agencies to ensure local groundwater resources are protected . Valley Water also supports groundwater sustainability through groundwater recharge operations, water conservation , and recycled water use. Additional details about constraints on groundwater supply and quality and Valley Water’s comprehensive groundwater management strategies are described in the 2021 Groundwater Management Plan (Appendix F).
In general, the Santa Clara and Llagas Subbasins have high -quality groundwater , with few exceptions, briefly discussed below.
Nitrate: Some wells in the Coyote Valley and Llagas Subbasin have elevated levels of nitrate from historic and ongoing sources including fertilizers, septic systems, and animal waste. Nitrate in the environment comes from both natural and anthropogenic sources. Small amounts of nitrate in groundwater (less than 10 mg/L) are normal, but higher concentrations suggest an anthropogenic origin. Common anthropogenic sources of nitrate in groundwater are fertilizers, septic systems, and animal waste. The maximum contaminant level (MCL) for nitrate in drinking DRAFT
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water is 10 mg/L as nitrogen . Since the Santa Clara Valley has a long history of agricultural production and septic systems are still in use in the unincorporated areas of the county, monitoring for nitrate contamination is an essential groundwater management function . The City’s groundwater nitrate concentrations are generally stable or declining and Valley Water has many programs to protect groundwater quality, including several targeted to improve nitrate in groundwater.
Per- and Polyfluoroalkyl Substances ( PFAS): PFAS are manufactured chemicals that have been used in industry and consumer products since the 1940s. The USEPA published a Final PFAS National Primary Drinking Water Regulation (NPDWR) on April 26, 2024, for six PFAS compounds which have been detected in drinking water across the nation. The rule became effective on June 25, 2024. To date, f ive of the six PFAS compounds have been detected in Santa Clara Subbasin and Llagas Subbasin water supply wells.
Valley Water continues to evaluate and analyze PFAS data from all sources including public water supply wells and Valley Water’s voluntary sampling programs. Since October 2020, staff from Valley Water and local water retailers and regulatory agencies have met regularly to discuss regional PFAS conditions, including impacted water supply wells. Valley Water will continue to collaborate with water retailers and regulatory agencies to better understand PFAS occurrence, evaluate potential sources, and identi fy any actions that may be needed to protect local water supplies.
7.1.2 Impacts of Climate Change
Impacts to the City’s supply reliability due to climate change are discussed in Section 6.10. The following discussion addresses climate change impacts to the City’s wholesalers.
SFPUC
Climate change has become an important factor in water resources planning in California and is frequently considered in urban water management planning, although the extent and precise effects of climate change remain uncertain. Increasing concentrations of GHGs have caused and will likely continue to cause a rise in temperatures around the world, which will result in a wide range of changes in climate patterns. Moreover, observational data show that a warming trend occurred during the latter part of the 20th century, the first quarter of the 21st century, and will likely continue through the end of the 21st century. Numerous studies have been conducted to determine the potential impacts of climate change on water resources. These climate change impacts are likely to affect both the Tuolumne River watershed and local watersheds in the Bay Area and include the following:
• Reductions in the average Sierra Nevada Mountain annual snowpack due to a rise in the snowline elevation and a shallower snowpack at lower elevations, and a shift in snowmelt runoff to earlier in the year;
• Changes in the timing, annual average, intensity, and variability of precipitation, and an increased amount of precipitation falling as rain instead of as snow; • Long-term changes in watershed vegetation and increased incidence of wildfires that could affect water quality and quantity;
• Sea level rise and an increase in saltwater intrusion; DRAFT
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• Increase in water temperatures with accompanying potential adverse effects on some fisheries and water quality;
• Increases in evaporation and concomitant increase in irrigation need; and • Changes in urban and agricultural water demand.
SFPUC Climate Change Study
The SFPUC views assessment of the effects of climate change as an ongoing need that requires regular updating to reflect improvements in climate science, atmospheric/ocean modeling, observations, and human response to the threat of GHG emissions. Climate change research by the SFPUC began in 2009 and continues to be refined.
The SFPUC partnered with The Water Research Foundation to develop the Long Term Vulnerability Assessment (LTVA) of the RWS. The study was conducted by the University of Massachusetts Amherst Hydrosystems Research Group with input from National Center for Atmospheric Research, other climate scientists, and Deltares. The goal of the LTVA is to help quantitatively and qualitatively assess to what extent climate change will be a threat to the RWS in comparison to, or in combination with, other external drivers of change over the next 50 years (2020-2070). The LTVA was completed in 2021 and amended in 2024.
The key findings of the LTVA are:
• Climate change exacerbates impacts from other external drivers of change and is not the single most important driver of vulnerability for the RWS. • The RWS at a baseline demand of 227 MGD is resilient to changes in climate and other external drivers.
• The RWS water supply performance declines with reductions in mean precipitation but is mostly insensitive to increases in temperature.
• The RWS is more vulnerable to changes in demand and instream flow requirements than changes in mean annual temperature and precipitation.
• The RWS is vulnerable to changes to mean climate when demand or regulatory instream flow requirements increase.
Further details of the LTVA can be found in Section 6 of the 2025 SFPUC UWMP, which can be found at https://www.sfpuc.gov/about-us/policies-plans/urban-water-management-plan.
Valley Water
Climate change impacts such as warming temperatures, shrinking snowpack, increasing weather extremes, and prolonged droughts pose significant challenges in water resources management, potentially including Valley Water’s operational flexibility and water s upply availability. Future increases in temperature will likely cause longer and deeper droughts. Precipitation will continue to exhibit high year -to year variability, with very wet and very dry years. Statewide and local changes in precipitation and temperature could significantly impact Valley Water’s water supplies and operations, the effectiveness of potential water supply investments, and water demand patterns. Specifically, Valley Water’s water supply vulnerabilities to climate change include:
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• Decreases in the quantity of imported water supplies. Currently the Sierra snowpack acts as a reservoir that captures precipitation as snow in the winter and releases it as runoff through the spring and summer where it is captured by reservoirs in the SWP and CVP system. More precipitation falling as rain and earlier snowmelt in the Sierra may exceed the storage capabilities of the existing SWP and CVP reservoirs , meaning much of this runoff would be lost as a water supply. Increases in temperature and evapotranspiration may also lead to a higher intensity of droughts, which can decrease imported water allocations. Rising air temperatures will also increase water temperatures in reservoirs and the Delta, which can lead to increased evaporation rates, a higher risk of harmful algal blooms, and negative impacts to fish and wildlife, all of which can impact the availability of imported water supplies for Valley Water. Sea level rise will also have negative impacts on imported water supplies, largely because of saltwater intrusion into the Delta . Saltwater intrusion can impact water supply allocations, as more fresh water will be needed to flow through the Delta and into San Francisco Bay to hold back saltwater, making it unavailable for CVP and SWP use. • Decreases in the ability to utilize local surface water supplies . Shifts in the timing and intensity of rainfall and runoff could affect Valley Water’s ability to capture and use local surface water supplies. It is difficult to capture rainfall when it comes in a few intense storms because reservoirs are more likely to fill and spill, or additional releases will be needed to make room for the storm flows. When it is wet, there are typically lower demands for water, so storm flows and releases to provide additional storage capacity are difficult to put to immediate use. Thus, even if average annual rainfall stays the same, the ability to utilize local supplies may decrease.
• Increases in irrigation and cooling water demands . Higher temperatures will increase irrigation demands for agricultural, residential, and commercial/institutional uses, which account for about 40% of water use in the county. Also, the county has several energy plants, multiple data centers, and facilities with cooling towers . Higher temperatures may also increase demands by these users.
• Decreases in water quality . Higher temperatures, wildfire, and changes in flow patterns could result in more algal blooms, and increased turbidity in imported and local surface water supplies. Sea level rise could also contribute to increased salinity in Delta conveyed supplies.
At a minimum, changes in water quality require additional monitoring . Often, degrading in water quality requires changes to treatment processes, and sometimes, can result in the interruption of supplies from the CVP or SWP.
• Increases in the severity and duration of droughts. Droughts are already Valley Water’s greatest water supply challenge . With increases in demands and potential reductions in supplies from climate change, this challenge will only grow . Without additional supplies and demand management measures, Valley Water would need to call for more frequent and severe water use reductions. These actions affect the economic and social well-being of the county. More severe and longer droughts will also affect the envi ronment. Valley Water needs to implement a water supply strategy that will adapt well to future climate change by managing demands, providing drought-resilient supplies, and increasing system flexibility in managing supplies and water quality.
Recognizing the challenges posed by climate change to water supply reliability, Valley Water has incorporated climate change impacts into future demand and supply projections for its water supply planning. In addition, Valley Water’s water supply strategy of managing demands, providing drought-resilient supplies, and increasing system flexibility helps adapt to future climate change.
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Furthermore, to address climate change impacts to ensure it can continue to provide a clean, reliable water supply, natural flood protection, and water resources stewardship in the future, Valley Water developed a Climate Change Action Plan (CCAP) . The CCAP provides goals, strategies, and actions for each of Valley Water’s mission areas, including water supply reliability, flood risk reduction, and water resources stewardship, as well as for emergency response . The goals and strategies developed through the CCAP planning process will guide the implementation of specific actions to address climate change . More information about the CCAP can be found at: https://www.valleywater.org/your-water/climate-change-action-plan.
For the implementation actions, Valley Water is actively promoting water conservation and reuse to increase resilience and mitigate climate change impacts . Valley Water’s long -term and comprehensive water conservation and demand management efforts are described in the Valley Water 2025 UWMP.
7.1.3 Additional Supply Constraints
Valley Water’s many supply sources are subject to hydrologic variability and additional constraints including regulatory and permit constraints, seismic threats to the Delta levee system, and infrastructure capacities. A summary of all constraints to Valley Water’s water supply sources is provided in more detail in Valley Water’s UWMP.
The SFPUC has identified additional potential constraints on water supplies that could affect the availability of water for the City. Additional constraints on SFPUC supplies are discussed below and in more detail in the SFPUC’s UWMP.
Bay-Delta Plan Amendment
In December 2018, the SWRCB adopted amendments to the Water Quality Control Plan for the Bay-Delta Plan (Bay -Delta Plan Amendment) to establish water quality objectives for the Bay - Delta watershed. The SWRCB is required by law to regularly review this plan. The adopted Bay- Delta Plan Amendment was developed with the stated goal of increasing salmonid populations in three San Joaquin River tributaries (the Stanislaus, Merced, and Tuolumne Rivers) and the Bay- Delta. The Bay-Delta Plan Amendment requires the release of 30-50% of the “unimpaired flow” on the three tributaries from February through June in every year type.
In SFPUC modeling of the new flow standard, it is assumed that the required release is 40% of unimpaired flow. If the Bay -Delta Plan Amendment is implemented, the SFPUC will be able to meet the projected water demands presented in their 2025 UWMP in normal years but is expected to experience supply shortages in single dry years or multiple dry years. Implementation of the Bay-Delta Plan Amendment could require rationing in all single dry years and multiple dry years.
Implementation of the Bay-Delta Plan Amendment remains uncertain for multiple reasons. • Over a dozen lawsuits have been filed in both State and Federal courts challenging the SWRCB’s adoption of the Bay-Delta Plan Amendment, including a legal challenge filed by the Federal government at the request of the USBR. This litigation is currently at the appellate level.
• The Bay-Delta Plan Amendment is not self-implementing and does not automatically allocate responsibility for meeting its new flow requirements to San Francisco or any other water rights holders. Rather, the Bay-Delta Plan Amendment merely provides a regulatory framework for DRAFT
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implementing water quality objectives, which must be accomplished by other regulatory and/or adjudicatory proceedings, such as a comprehensive water rights adjudication or, in the case of the Tuolumne River, may be implemented through the water quality cer tification process set forth in section 401 of the Clean Water Act as part of the Federal Energy Regulatory Commission’s licensing proceedings for the Don Pedro and La Grange hydroelectric projects.
It is currently unclear when the license amendment process is expected to be completed. This process and the other regulatory and/or adjudicatory proceedings may face legal challenges and have lengthy timelines, and quite possibly could result in a different assignment of flow responsibility (and therefore a different water supply impact on the City).
In recognition of the obstacles to implementation of the Bay-Delta Plan Amendment, the SWRCB Resolution No. 2018 -0059 adopting the Bay -Delta Plan Amendment directed staff to help complete a “Delta watershed-wide agreement, including potential flow measures for the Tuolumne River,” and to incorporate such agreements as an “alternative” for a future amendment to the Bay- Delta Plan to be presented to the SWRCB “as early as possible after December 1, 2019.” On March 26, 2019, the SFPUC adopted Resolution No. 1 9-0057 to support the SFPUC’s participation in the Voluntary Agreement negotiation process. To date, those negotiations are ongoing under the California Natural Resources Agency and the leadership of the Newsom administration. On November 10, 2022, the SFPUC along with the Modesto and Turlock Irrigation Districts signed a Memorandum of Understanding Advancing the Term Sheet for the Voluntary Agreements to Update and Implement the Bay -Delta Water Quality Control Plan and Other Actions. Voluntary Agreements are now referred to as the Agreements to Support Healthy Rivers and Landscapes and negotiations remain ongoing.
Because of the uncertainty surrounding implementation of the Bay -Delta Plan Amendment, the water service reliability assessment in the SFPUC’s 2025 UWMP looks at two future supply scenarios:
• Implementation of the Bay-Delta Plan Amendment, and
• SFPUC system’s current conditions without implementation of the Bay -Delta Plan Amendment.
The two scenarios provide a bookend for the possible future scenarios regarding RWS supplies.
Since the Bay-Delta Plan Amendment implementation start date is unknown, for the purposes of the supply reliability analysis, it is included in the 2030 modeling scenarios.
Per the Valley Water 2050 WSMP, if SFPUC supplies were to be reduced significantly due to the Bay-Delta Plan Amendment, it could have ramifications for Valley Water’s future water supply outlook and investment strategy.
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7.2 Regional Supply Reliability
The City relies mostly on SFPUC and Valley Water for its water supply and is directly affected by the water supply conditions each wholesaler faces. The following describes the measures each wholesaler is taking to ensure regional supply reliability.
7.2.1 SFPUC
Tier 1 Drought Allocations
The WSA between the SFPUC and the wholesale customers, discussed previously in Section
6.1.1, includes as “Attachment H” a Water Shortage Allocation Plan (WSAP), also known as the Tier 1 Shortage Plan. This plan describes the method for allocating water from the RWS between the SFPUC’s retail customers, on the one hand, and the wholesale customers collectively, on the other, during system-wide shortages caused by drought. The Tier 1 Shortage Plan applies only when the SFPUC determines that a system -wide water shortage due to drought exists, as set forth in a declaration of water shortage emergency by the SFPUC; in the absence of such a declaration, the SFPUC also may opt to request voluntary cutbacks from its retail and wholesale customers to achieve water use reductions. The SFPUC and the wholesale customers most recently amended the Tier 1 Shortage Plan in 2025.
The SFPUC allocates water under the Tier 1 Shortage Plan when it determines that the projected available water supply is less than projected system -wide water purchases for the upcoming Supply Year, defined as the period from July 1 through June 30. The following table shows the retail customers’ share and the wholesale customers’ share of the annual water supply available during shortages depending on the level of system -wide reduction in water use that is required.
If the SFPUC determines that the level of system-wide reduction required during a shortage is greater than 20%, the SFPUC and the wholesale customers will meet to discuss the appropriate retail and wholesale customers’ shares of available water – also known as the retail and wholesale customers’ Tier 1 Allocations. The wholesale customers’ Tier 1 Allocation will be apportioned among the individual wholesale customers based on a separate methodology, known as the Tier 2 Drought Response Implementation Plan (Tier 2 Plan), which is separately adopted by all the wholesale customers without the SFPUC’s involvement as discussed further below.
Table 7-1: SFPUC Tier 1 Drought Allocations
Level of System-Wide Reduction
in Water Use Required
Share of Available Water
SFPUC Retail Customers’ Share Wholesale Customers’ Share 5% or less
6% through 10%
11% through 15%
16% through 20%
35.5%
36.0%
37.0%
37.5%
64.5%
64.0%
63.0%
62.5%
The Tier 1 Shortage Plan allows for voluntary transfers of shortage allocations between the SFPUC and any wholesale customer as well as between wholesale customers themselves. In addition, voluntary transfers of water “banked” by the SFPUC or a wholesale customer, through reductions in usage greater than required, may occur.
Under the Tier 1 Shortage Plan if the retail customer s’ Tier 1 Allocation results in the retail customers receiving a “positive allocation” (i.e., a supply of additional water rather than a required DRAFT
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reduction in water use), then the excess percentage for retail is re -allocated to the wholesale customers’ Tier 1 Allocation. The retail customers are also required to conserve a minimum of 5% for any level of reduction in system-wide water use. The additional water conserved by retail customers up to the minimum 5% level is deemed as remaining in RWS storage for inclusion in the calculation of projected available water in future successive dry years.
The Tier 1 Shortage Plan will expire at the end of the term of the WSA in 2034, unless the SFPUC and the wholesale customers mutually agree to revise or terminate it prior to that date.
Tier 2 Drought Allocations
The wholesale customers have negotiated and adopted the Tier 2 Plan, referenced above, which allocates the wholesale customer Tier 1 Allocation from the Tier 1 Shortage Plan among each of the 26 wholesale customers. These Tier 2 Allocations are based on a formula that takes into account multiple factors for each wholesale customer including:
• Residential population;
• Non-residential “base” (i.e., indoor) use;
• Seasonal uses;
• Total RWS purchases in recent non-drought years; and
• ISG.
The Tier 2 Plan employs a structured, sequential, five -step method to allocate water to each wholesale customer. The allocations are constrained by minimum and maximum cutbacks, which establish the maximum final allocation and minimum guaranteed final allocation, respectively. No agency's final allocation can fall outside of these bounds. The allocation then proceeds by prioritizing indoor uses.
The subsequent steps systematically allocate the remaining available water based on different customer demands. First focusing on indoor demand, water is allocated based on an agency’s residential population and the State residential efficient indoor standard (47 gallons per person per day [gpcd] in 2025), followed by an allocation based on non -residential “base” (i.e., indoor) use. A limited amount of water is allocated based on seasonal use (e.g., cooling towers and irrigation). Finally, the remaining supply is allocated based on a weighted share of two -thirds RWS purchases in the recent non-drought years and one-third ISG.
The result of the Tier 2 Plan is each wholesale customers’ proportion, expressed as a percentage, of the available Tier 1 Allocation (Allocation Factor).
The Tier 2 Plan requires that the Allocation Factors be calculated by BAWSCA each year in preparation for a potential water shortage emergency. As the wholesale customers change their water use characteristics (e.g., increases or decreases in RWS purchases and use of other water sources, changes in monthly water use patterns, or changes in population), the Allocation Factor for each wholesale customer will also change. However, for long-term planning purposes, each wholesale customer may use as its Allocation Factor, the value identified in the Tier 2 Plan when adopted.
The Tier 2 Plan was renegotiated and adopted by all wholesale customers in 2025.
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SFPUC Water System Improvement Program (WSIP)
Initiated in 2008, SFPUC’s Water System Improvement Program (WSIP) is a $4.8 billion, multi - year capital program to upgrade the RWS as well as the SFPUC’s local water system. The program is delivering capital improvements that enhance the SFPUC’s ability to provide reliable, affordable, high quality drinking water in an environmentally sustainable manner to its retail and wholesale customers. The SFPUC structured the WSIP to cost -effectively meet water quality requirements, improve seismic and delivery reliability goals through the year 2030, and fulfill water supply objectives through the year 2018. The SFPUC completed the San Francisco portion of the WSIP in October 2020. As of June 30, 2025, the regional portion of the WSIP was 99.3% complete, having repaired, replaced, and seismically upgraded crucial portions of the RWS; only two regional projects remain in planning and construction, while 49 regional projects have been completed or are in close -out. The SFPUC forecasts that the overall WSIP will be complete in June 2032.
The SFPUC undertook the WSIP to ensure the ability of the RWS to meet Level of Service (LOS) Goals and Objectives for water quality, seismic reliability, delivery reliability, and water supply.
The Water Supply LOS goal, stated in the WSIP and adopted in 2008, is to meet customer water needs in non-drought and drought periods. The SFPUC amended and updated the LOS Goals and Objectives in November 2023. The SFPUC’s current LOS Goals and Objectives related to water supply include the following:
• Meet an average annual water demand of 265 MGD from the SFPUC watersheds for retail and wholesale customers during non-drought years consistent with the WSA. • Meet dry -year delivery needs while limiting rationing to a maximum 20 % system-wide reduction in water service during extended droughts.
• Diversify and improve use of new water sources and drought management, including groundwater, recycled water, conservation, transfers, storage expansion, purified water, desalinated water, and technological innovations that can increase supply and/or water use efficiency.
• Maintain San Francisco retail residential potable water use below 45 gpcd. • Realize annual Real Water Losses of less than 10% of water supplied to San Francisco. • Meet 80% of San Francisco’s Recreation and Parks Department irrigation demands with recycled water by December 31, 2025.
WSIP Dry Year Water Supply Projects
With the WSIP, the SFPUC has undertaken several water supply projects to meet dry -year demands. Those projects include the following:
• Calaveras Dam Replacement Project. Calaveras Dam is in the East Bay near a seismically active fault zone, and following the Loma Prieta earthquake in 1989, it was determined to be seismically vulnerable. To address the dam’s vulnerability, the SFPUC constructed a new dam of equal height downstream of the existing dam. This project was completed in 2022.
Calaveras Reservoir was completely refilled in 2023 and is now operating at full capacity. • Alameda Creek Recapture Project. The Alameda Creek Recapture Project includes new facilities in and around an existing quarry pit in Sunol Valley to recover the loss of water supply DRAFT
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associated with instream flow release and bypass requirements related to the Calaveras Dam Replacement Project. The project is anticipated to be completed in 2032. • Lower Crystal Springs Dam Improvements. The Lower Crystal Springs Dam Improvements Project was completed in May 2012. The related joint San Mateo County/SFPUC Bridge Replacement Project to replace the bridge across the Lower Crystal Springs Dam was completed in January 2019.
• Regional Groundwater Storage and Recovery Project. The Regional Groundwater Storage and Recovery (RGSR) Project is a strategic partnership between the SFPUC and three wholesale customers in San Mateo County: the California Water Service Company (serving South San Francisco and Colma), the City of Daly City, and the City of San Bruno.
The project sustainably manages groundwater and surface water resources to provide the RWS with additional supplies during times of drought. During years of normal or heavy rainfall, the SFPUC provides additional surface water from the RWS to the three agencies in northern San Mateo County, allowing them to reduce the amount of groundwater that they pump from the southern Westside Groundwater Basin. Over time, the reduced pumping allows the aquifer to naturally recharge and result in increased groundwater storage of up to 61,000 AF of new water supply available during dry years. As of December 2025, the SFPUC had accumulated approximately 14 billion gallons of groundwater sto rage credits (about 43,093 AF) through the project.
The RGSR project has two phases. Phase 1, which included building 13 production wells and treatment facilities, is complete. Phase 2 design began in early 2020 and covers rehabilitating and reinstalling well pumps, installing two new variable frequency drivers, and conducting start-up testing and well disinfection. Pumps at the Hickey, Southwood Drive, and Mission wells were rehabilitated, packed, and stored due to staff shortages, operational challenges, and elevated ammonia levels at the Southwood Driv e Well; they may be reinstalled later.
Construction on Phase 2B began in 2024 and would transport groundwater from SFPUC South San Francisco Main Well to California Water Service Company Treatment Station in South San Francisco. The project will make improvements at the existing well site which includes mechanical, electrical, structural, and corrosion protection upgrades. The SFPUC also prepared a conceptual engineering report and initiated design work for additional treatment to address the high ammonia levels at the South Spruce Lane Well and Treatment Facility. Minor amounts of groundwater pumping from RGSR wells have occurred during start- up testing and monthly maintenance.
• Regional Groundwater Treatment Improvements Project. The SFPUC approved this new project in the 10-Year Water Enterprise Capital Improvement Program for FY 2021-2030. The project includes treatment facilities for several of the RGSR project wells to address groundwater quality issues that have emerged since the wells were constructed. • Water Transfers. During the planning and implementation of the WSIP, the SFPUC pursued a long-term agreement to transfer 2 MGD from Modesto Irrigation District to the SFPUC in drought years. Negotiations with Modesto Irrigation District ended in 2012 when an agreement could not be reached. The dry-year transfer project is now being included as part of the new SFPUC Alternative Water Supply Program and is described in further detail below.
Alternative Water Supply Planning Program
In 2019, the SFPUC established the Alternative Water Supply (AWS) Program to identify and plan water supply and storage projects and actions that increase the dry -year reliability of the RWS.
Based on the 2045 planning horizon that the SFPUC applied in its February 2024 AWS Plan, the DRAFT
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SFPUC anticipates a water supply gap will occur in future dry years. The AWS Program aims to help fill the gap through local and regional capital projects. The February 2024 AWS Plan identified six regional projects that might partially address the future water supply gap and the priorities for this planning effort. Since the development of that plan, three projects have been deferred (Daly City Recycled Water Expansion, Alameda County Water District -Union Sanitary District Purified Water, and Calaveras Reservoir Expansion) and one project has been canceled (Los Vaqueros Reservoir Expansion). The AWS Program is continuing to pursue the following two projects:
• PureWater Peninsula. PureWater Peninsula (formerly known as the Crystal Springs Purified Water Project) is a purified water project that could provide 6 MGD of additional potable water supply to the RWS through surface water augmentation at the SFPUC’s Crystal Springs Reservoir. The currently proposed project involves treating wastewater effluent from Silicon Valley Clean Water at a new advanced purified water facility located on the Peninsula and transmitting that purified water to Crystal Springs Reservo ir, where it would blend with RWS surface water supplies before the SFPUC treats it again at Harry Tracy Water Treatment Plant. A future phase could provide an additional 6 MGD of additional potable water supply to the RWS. Project partners include the SFPUC, Silicon Valley Clean Water, BAWSCA, Mid- Peninsula Water District, California Water Service Company, City of Redwood City, City of Foster City, and City of San Mateo.
• South Bay Purified Water. In 2023, the SFPUC, the City of San Jose, and the City of Santa Clara completed an initial feasibility study for the South Bay Purified Water project, envisioned as a 10 MGD purified water project that would serve the local demands of San Jose and Santa Clara during all types of water years and deliver an additional volume of water supply to the RWS in dry years. Currently, Valley Water is working with San Jose and Santa Clara to design a larger project to meet broader regional needs. The SFPUC’s participation in this project will be based on the regional benefits to the RWS customers.
If both AWS projects that SFPUC staff has identified through the current planning process can be implemented, there would still be a supply shortfall to meet projected needs associated with implementation of the Bay -Delta Plan Amendment. Furthermore, both alternative water supply options are in the planning phase and are subject to changes in institutional structure and design.
Given the limited availability of water supply alternatives, unless the supply risks are significantly reduced, the SFPUC will continue to plan, develop, and implement all potential projects that can help bridge the anticipated water supply gap during droughts.
Outside of the AWS Program, the following additional regional projects are included in the Agreements to Support Healthy Rivers and Landscapes discussed in the Bay -Delta Plan Amendment section above. Progress on these water supply options will be guided by scientific monitoring and collaborative decision making.
• Groundwater Banking. Groundwater banking projects in the Modesto Irrigation District and Turlock Irrigation District service areas could provide the SFPUC with some additional water supply to meet instream flow releases in dry years, reducing water supply impacts on the RWS. A feasibility study of this option is included in the Agreements to Support Healthy Rivers and Landscapes.
• Inter-Basin Collaborations. Inter-Basin Collaborations could include establishing a partnership between interests on the Tuolumne River (such as the SFPUC) and those on the Stanislaus River, which would allow responsibility for streamflow to be assigned variably based on the annual hydrology. The Tuolumne system tends to spill more excess flow in DRAFT
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wetter years than the Stanislaus system, and this excess flow could be shaped and credited to meet Stanislaus system requirements, while New Melones Reservoir in the Stanislaus system is refilling. Then the stored water could be partially used to provide required streamflow to meet Stanislaus and Tuolumne requirements in future dry years. • Dry-Year Transfers. The SFPUC initiated discussions with irrigation districts under the WSIP to secure a dry -year transfer (see WSIP Dry -Year Water Supply Projects section above).
While no transfer was secured, the SFPUC continues to engage in discussions with irrigation districts to explore potential transfer opportunities.
The SFPUC’s AWS Plan published in February 2024 included a planning framework for the SFPUC to consider water supply needs and related tradeoffs; guide the decisions to proceed with environmental review; and continue the development of projects that can be st meet anticipated water supply needs. In June 2025, the SFPUC prepared a progress report that provided status updates on the AWS projects. In 2027, the SFPUC plans to review and revise its AWS Plan based on updated information.
Regional Water Demand and Conservation Projections
In December 2025, BAWSCA completed the Regional Water Demand and Conservation Projections Report (Demand Study). The goal of the Demand Study was to develop transparent, defensible, and uniform demand and conservation savings projections for each wholesale customer using a common methodology to support both regional and individual agency planning efforts and compliance with the new statewide water efficiency targets required by AB 1668 and SB 606.
Through the Demand Study process, BAWSCA and the wholesale customers:
• Quantified the total average-year water demand for each wholesale customer through 2050, • Quantified passive and active conservation water savings potential for each individual wholesale customer through 2050, and
• Identified conservation programs with high water savings potential and/or BAWSCA Member Agency interest.
Implementation of these conservation measures, along with passive conservation, is anticipated to yield an additional 16.14 MGD of water savings by 2050. Based on the revised water demand projections, the identified water conservation savings, increased development and use of other local supplies by the wholesale customers, and other actions, the collective purchases of the BAWSCA Member Agencies from the SFPUC are projected to stay below 184 MGD through 2050.
As part of the Demand Study, each wholesale customer was provided with a demand model that can be used to support ongoing demand and conservation planning efforts, including UWMP preparation.
BAWSCA’s Strategy 2050 Future Water Supply Projects and Programs The SFPUC is supporting BAWSCA in the development of its Long-Term Reliable Water Supply Strategy 2050 (Strategy 2050), a regional assessment of Member Agencies’ water supply needs.
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for the BAWSCA region and establish a framework to collectively support water reliability and resilience. The main objectives of Strategy 2050 include:
• Providing a comprehensive picture of the region's supply and demand management needs and options;
• Establishing a framework for collectively maintaining and improving regional water supply reliability and resilience;
• Elevating awareness of and supporting the region’s interests in new and emerging regulations that impact water supply and demand management;
• Expanding regional dialogue and collaboration to collectively address common needs; • Closing the gap on funding needed for water supply resilience and reliability; and • Supporting availability of affordable water supplies and demand management strategies to all customers.
Strategy 2050 is actively evaluating opportunities to enhance water supply reliability in the BAWSCA region, including projects involving physical infrastructure and actions involving non - infrastructure interventions, such as policies, programs, and/or con tractual agreements. A total of 70 local and regional projects and actions will be considered, including stormwater capture projects, technical assistance programs for onsite reuse, groundwater banking partnerships, new and replacement well projects, and interties development and optimization, among others.
Strategy 2050 plan is anticipated to be completed by 2027. From 2027 onward, the Strategy 2050 effort is anticipated to involve implementing the actions identified in the plan, tracking and reporting on the progress, and incorporating the findings from th e implementation activities into BAWSCA’s following fiscal year Work Plan.
7.2.2 Valley Water
To maintain water supply reliability and flexibility, Valley Water's water supply includes a variety of sources including natural groundwater recharge, local surface water, imported water from the State and Federal projects, and recycled and purified water . Valley Water has an active conjunctive water management program to optimize the use of groundwater and surface water, and to prevent groundwater overdraft and land subsidence.
Valley Water’s basic water supply strategy to compensate for supply variability is to store excess wet year supplies in the groundwater basin, local reservoirs, San Luis Reservoir, and/or Semitropic Groundwater Bank, and draw on these reserve supplies during dry years to help meet demands. These reserves, along with existing and planned future projects in the 2050 WSMP, help Valley Water meet demands during a prolonged drought.
Valley Water’s LOS goal is to meet 100% of annual water demand during non-drought years and at least 80% of annual water demand in drought years . Future projects and programs recommended in the 2050 WSMP, including additional long -term water conservation savings, potable reuse, recharge capacity increases, and banking and storage, were developed in accordance with this policy to minimize the need to call for water use reductions greater than 20%. As part of the ongoing master planning process to address future uncertainties wit h demands, existing supplies, and proposed projects, Valley Water conducts annual evaluation of DRAFT
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WSMP projects to determine which projects should continue to be invested in to meet the LOS goal and potentially for other benefits such as operational flexibility, supply diversification, and resiliency to future uncertainties.
7.2.3 Groundwater
The City’s water supply includes groundwater pumped from a conjunctively managed groundwater basin. The groundwater basins in Santa Clara County span nearly 400 square miles, with thousands of well users pumping groundwater for beneficial use . Protecting the local groundwater basins is critical to maintaining water supply reliability in the County of Santa Clara.
The City relies on Valley Water activities to maintain sustainable supplies, including managed groundwater recharge and in -lieu groundwater recharge (e.g., treated surface water deliveries, demand management programs, and SFPUC supply). Valley Water’s 2050 WSMP ensures that local groundwater resources are sustained and protected . Groundwater management encompasses activities and programs that identify and mitigate co ntamination threats to the groundwater basin, replenish and recharge groundwater supplies, prevent groundwater overdraft and land subsidence, and sustain storage reserves. Valley Water programs to sustain and protect groundwater resources are described in detail in their 2050 WSMP.
7.3 Water Service Reliability Assessment
The City’s water service reliability was assessed by comparing supplies and demand s under an average/normal year, a single dry year, and five consecutive dry years. The following section describes the basis and results of the City’s water service reliability assessment.
7.3.1 Year Type Characterization
There are three year-types included in the water service reliability assessment. These include:
Average/Normal Year
The “normal” year for the purposes of this Plan, is a year in the historical sequence that most closely represents median runoff levels and patterns. For planning purposes, the SFPUC “normal year” is based on historical hydrology under conditions that allow the RWS reservoirs to be filled over the course of the snowmelt season, allowing full deliveries to their customers.
The SFPUC used its Hetch Hetchy and Local Simulation Model (HHLSM) to perform the water supply analyses presented in their 2025 UWMP. HHLSM combines a historical record of hydrology from 1920 through 2025 with a current representation of RWS infrastructur e and operations.
Valley Water used the Water Evaluation and Planning (WEAP) model , developed by Stockholm Environment Institute, to assess their water service reliability and determine base years for all year types. Valley Water’s WEAP water supply planning model operates on a monthly time-step that simulates the water supply and demand over 100 years, using the historic hydrologic sequence of 1922 through 20 21. Valley Water used the average annual supply over the 100 modeled years to represent the average year condition.
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The City selected the average of the period from 1922-2021 as a representation of a “normal” or “average” water year to stay consistent with the average year determined by Valley Water.
Single Dry Year
The single dry year supply is defined as the year with the minimum usable supply. The hydrology of 1977 represents the minimum total supply that has been observed in the historical record, according to Valley Water.
The City selected 1977 as the single dry year since groundwater managed by Valley Water will be relied upon to make up any deficit from water wholesalers.
Five-Consecutive-Year Drought (Multiple Dry Year)
An analysis of a multiple dry year scenario is particularly useful in the evaluation of carryover storage. Evaluating the availability of the county’s water supplies requires an understanding of the driest periods that can reasonably be expected to occur . The SFPUC combined historical data with a hypothetical drought more severe than what the RWS has historically experienced to assess reliability over a multi -year drought. The design drought sequence used by the SFPUC for reliability planning is an 8.5-year period comprised of:
• Historical hydrology from July 1987 to June 1992;
• A prospective drought that includes the 1976 -77 drought (to represent a drought sequence worse than historical); and
• A system recovery period for the last six months of the design drought.
While the 2012-2016 and 2020-2023 droughts include some of the driest years on record for the SFPUC’s watersheds, the design drought still represents a more severe drought in duration and overall water supply deficit.
Valley Water’s WEAP modeling results indicate that the county’s water supply system is more vulnerable to successive dry years, such as those that occurred in 1988 through 1992 and in 2012 through 2016. Valley Water chose the period from 1988 to 1992 as their five dry-year base period, which was an extended and more severe drought within historic record and WEAP modeling period.
The City chose 1988 to 1992 as the five -year drought base period to match the period used by Valley Water and SFPUC.
Table 7-2 presents the base years for each of the three conditions described above.
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Table 7-2: Basis of Water Year Data
Year Type Base Year1
Average Year 1922-2021
Single-Dry Year 1977
Five Consecutive Dry Years 1st Year 1988
Five Consecutive Dry Years 2nd Year 1989
Five Consecutive Dry Years 3rd Year 1990
Five Consecutive Dry Years 4th Year 1991
Five Consecutive Dry Years 5th Year 1992
Note:
1. All base years are consistent with Valley Water.
7.3.2 Supply and Demand Comparison
This section utilizes the water demand projections presented in Section 4 and water supply projections presented in Section 6 to assess the City’s water service reliability in all scenarios outlined in Table 7-2. As discussed in Section 4 and Section 6 , both demand and supply projections incorporate potential impacts associated with climate change. The reliability analysis assumes reduced supply from SFPUC from the implementation of the Bay-Delta Plan, described above in Section 7.1.3. The Bay-Delta Plan would require 30-50% unimpaired flow; however, because the plan is currently in negotiation, the timing of implementation remains uncertain. For the purposes of the 2025 UWMP analysis, the SFPUC assumed implementation beginning in 2030.
The SFPUC has conducted an analysis of the RWS supply reliability under both conditions, with and without 40% unimpaired flow . The SFPUC also modeled two separate cutback scenarios:
one based on the actual projected wholesale demands through 2045 and another scenario based on the wholesale contract amount of 184 MGD. The City is reporting the more conservative modeled scenario based on Bay-Delta Plan implementation in 2030 and projected demands for consistency with the SFPUC UWMP; however, the SFPUC has acknowledg ed the contractual obligation to supply 184 MGD to the wholesale customers during non-drought years and thus has retained the second modeled scenario for planning purposes . Both SFPUC modeled scenarios are provided in Appendix H.
Valley Water ’s supply reliability analysis is based on historic hydrology, as described in the previous section. Projected supplies are based on Valley Water’s 2050 WSMP recommended lower cost portfolio, which includes semitropic storage (350,000 AF) through 2035, groundwater banking (250,000 AF) starting in 2040, Sisk Reservoir expansion in 2035 , Delta Conveyance Project in 2045, and Pure Water Silicon Valley in 2035 . Valley Water modeled data is provided in Appendix H.
Recycled water is a drought -proof source of supply and is assumed to have equal supply and demand in all scenarios, thus not affecting potable water. Projected recycled water demands for 2045 assume an increase in recycled water use of approximately 630 AF compared to 2025; however, to be conservative, no adjustments were made to projected potable irrigation demand, even though customers converting to recycled water irrigation would be expected to offset potable water irrigation demand. Since the City is largely built-out, expansion of the recycled water system DRAFT
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would likely be accompanied by a corresponding reduction in potable water demand, which would result in lower projected demand.
Note that the total groundwater availability is shown in all year types ; however, the actual production will only supplement wholesaler supplies as needed and for water quality/maintenance purposes.
Normal Year
Table 7-3 presents the water service supply reliability assessment for a normal water year based on water supply and demand projections . During normal water years, water supplies are adequate to meet projected demands despite implementation of the Bay-Delta Plan.
Table 7-3: Normal Year Supply and Demand Comparison (AFY) 2030 2035 2040 2045
Supply Totals1 30,081 32,624 34,409 35,526
Demand Totals2 21,334 24,198 26,625 29,014
Difference 8,747 8,426 7,784 6,512
Notes:
1. Includes total groundwater well capacity.
2. Projected demands include passive conservation.
3. Includes potable and recycled water.
Single Dry Year
The SFPUC is expecting up to 30% cutbacks to supply in a single critical dry year from 2030 through 2045, assuming implementation of the Bay-Delta Plan in 2030. This translates to slightly deeper cutbacks for retailers and the City can expect up to a 37% cutback. For a single dry year prior to the assumed implementation of the Bay-Delta Plan, the SFPUC is expecting no shortages of RWS supplies and therefore no cutbacks to retailers.
Valley Water supplies are projected to be sufficient to meet demands during a single dry year through 2045. This assumes that reserves are at healthy levels at the beginning of the year and that the projects and programs identified in Valley Water’s 2050 WSMP are implemented . As such, the City assumed no reduction in supply from Valley Water during a single dry year . It is noted that there may be voluntary cutbacks in dry years that the City would actively promote to customers in the interest of overall water conservation efforts.
In the case of a single dry year, the City projects no reduction in supply availability from groundwater. The resulting analysis of available supplies shows no projected shortfalls ( Table 7-4).
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Table 7-4: Single Dry Year Supply and Demand Comparison (AFY) Parameter 2030 2035 2040 2045
Supply Totals1,2 26,340 28,499 29,697 30,333
Demand Totals3 21,334 24,198 26,625 29,014
Difference 5,006 4,301 3,072 1,319
Notes:
1. Includes interruption from SFPUC due to Bay-Delta Plan in 2030 and Tier 2 reduction plan.
2. Includes total groundwater well capacity.
3. Projected demands include passive conservation.
4. Includes potable and recycled water.
Multiple Dry Year
The SFPUC has indicated that during multiple dry years retailers can expect cutbacks as high as 47% of normal SFPUC supplies by the second year of a five -year drought beginning in 2045.
SFPUC supply and retail cutbacks are detailed in Appendix H.
Valley Water indicated in their 2025 UWMP that with existing and planned projects’ supplies, Valley Water’s diverse water supplies are sufficient to meet demands throughout the first three- year period in a five-year drought in all demand years without having to call for short -term water use reductions. However, supply shortages are projected in the fourth and fifth years of a five- year drought period beginning in 2030 and 2045, which may result in reductions to the City’s supply allocation . For planning purposes, the City assume d Valley Water supply cutbacks proportional to the ratio of projected shortage to projected demand identified in Valley Water’s multiple dry year analysis.
The City does not anticipate any reduction in groundwater availability during a five-year drought.
As such, the City would be able to increase the amount of groundwater pumped to offset anticipated deficiencies from other sources . The City’s groundwater basin is not adjudicated, which means the right to pump groundwater from the basin has not been given by judgment of a court or board. During a critical five dry year event, voluntary and mandatory conservation measures would be expected to reduce potable water demand and therefore, reduce the amount of groundwater needed to supplement supply.
Table 7-5 details the results of the multiple dry year analysis. Based on the anticipated cutbacks to SFPUC and Valley Water supplies, and considering maximum groundwater well capacity, the City is able to meet demands in all year types from 2030-2040, with shortages only up to 4% anticipated in years two through five of a five-year drought beginning in 2045.
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Table 7-5: Multiple Dry Years Supply and Demand Comparison (AFY) Year Parameter 2030 2035 2040 2045
First
year
Supply totals 26,340 28,499 29,697 30,333
Demand totals 21,334 24,198 26,625 29,014
Surplus/(shortfall) 5,006 4,301 3,072 1,319
Second
year
Supply totals 25,013 27,262 28,373 28,935
Demand totals 21,334 24,198 26,625 29,014
Surplus/(shortfall) 3,679 3,064 1,748 (79)
Third
year
Supply totals 25,013 27,262 28,373 28,935
Demand totals 21,334 24,198 26,625 29,014
Surplus/(shortfall) 3,679 3,064 1,748 (79)
Fourth
year
Supply totals 24,192 27,262 28,373 27,977
Demand totals 21,334 24,198 26,625 29,014
Surplus/(shortfall) 2,858 3,064 1,748 (1,037)
Fifth
year
Supply totals 24,419 27,262 28,373 28,272
Demand totals 21,334 24,198 26,625 29,014
Surplus/(shortfall) 3,085 3,064 1,748 (742)
Notes:
1. Includes interruption from SFPUC due to Bay-Delta Plan in 2030 and Tier 2 reduction plan.
2. Projected demands include passive conservation.
3. Includes total groundwater well capacity.
SFPUC has indicated that implementation of the AWS Program and associated potential projects is expected to reduce anticipated supply shortfalls, which could translate to smaller cutbacks to retailers. Valley Water has indicated that potential shortages may be addressed through supply augmentation measures rather than relying solely on demand reduction, which could also reduce potential cutbacks to the City’s Valley Water supply.
Actual availability of each supply during any given year depends on hydrology, groundwater recharge operations and conditions, and other factors . The water supply available to individual retailers will ultimately be determined by Valley Water and SFPUC . The City will work closely with Valley Water, SFPUC, and other water retail agencies to implement any stages of action to reduce the demand for water during water shortages. Any supply deficit would be compensated for by increased conservation levels thro ugh marketing and implementation of Demand Management Measures (DMMs) (see Section 9) and restrictions in consumption dictated by the City’s Water Shortage Contingency Plan (see Section 8).
7.4 Drought Risk Assessment
The City i s required to prepare a Drought Risk Assessment (DRA ) that compares total water supply sources available to projected water use to assess the City’s water service reliability and risk. The following section describes the City’s DRA under a drought period lasting for the next five consecutive years. The DRA is intended to be a stand-alone section of the UWMP and thus, information regarding supply and demand are duplicated herein.
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7.4.1 Data, Methods, and Basis for Water Shortage Condition DRA Data
The DRA was based on the five driest consecutive years on record. The City chose to use 1988 to 1992 as the base period for the DRA based on Valley Water’s WEAP modeling analysis. This period represents an extended drought within historic record and WEAP modeling period . The DRA assumes those driest years occur over the next five years, from 2026 through 2030.
The DRA evaluation was developed using data and modeling provided by SFPUC and Valley Water for a five -year consecutive drought . The DRA can be updated as needed, based on updated supply and demand data and unforeseen regulatory changes.
The expected gross water use (potable and recycled) for the next five years is based on a linear interpolation between 2025 actual water use and projected 2030 water use. Actual gross water use within the City’s service area in 2025 is approximately 18,806 AF. The potable water use projection for 2030 was based on the BAWSCA Regional Water Demand and Conservation Study, December 2025 (Demand Study) and projected additional demand from planned new development and redevelopment within the City’s service area . The Demand Study projections were developed using a hybrid water demand forecasting framework that integrates econometric modeling with conservation accounting tools. The projections from the Demand Study used in this DRA considered expected service area population , climate change conditions, water rates, and economic growth as well as passive conservation from plumbing codes and fixture turnover over time . The full description of the econometric modeling and water demand forecasting framework is included in the Demand Study, attached as Appendix C. Projected recycled water use is based on anticipated recycled water development. The City’s projected gross water use in 2030 is 21,334 AF.
The City has three sources of potable water supply: purchased surface water from SFPUC, purchased treated surface water from Valley Water, and groundwater from six City -owned and operated wells. The breakdown of total potable supply by source is outlined in Section 6.8, Table 6-9, and was determined using the City’s contractual agreements with each wholesaler, projected demands provided to each wholesaler, and historical production trends . Although the supply projections for SFPUC are based on the City’s projected demand , t he City’s contractual agreement with SFPUC is 14,100 AFY . Supply projections from Valley Water are based on projected demands and historical production trends. The City can purchase additional available water from Valley Water during non -dry years when water is available . Groundwater supply is based on the City’s sustainable yield of 8,000 AFY.
Recycled water (non -potable) is supplied by the City’s Water Pollution Control Plant (WPCP).
Recycled water is a drought -proof source of supply and is assumed to have equal supply and demand in all scenarios, thus not affecting potable water. Projected recycled water demands for 2045 assume an increase in recycled water use of approximately 630 AF compared to 2025; however, to be conservative, no adjustments were made to projected potable irrigation demand, even though customers converting to recycled water irrigation would be expected to offset potable water irrigation demand. Since the City is largely built-out, expansion of the recycled water system would likely be accompanied by a corresponding reduction in potable water demand, which would result in lower projected demand.
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DRA Methods
The percentage of water supply volume available during a five -year consecutive drought was based on the information provided by the SFPUC and Valley Water, found in Appendix H. The SFPUC has indicated that there are sufficient supplies to serve retailer demands in the event of a five-year drought starting in 2026. The recycled water and groundwater projects that the SFPUC has planned for implementation within the next five years were integrated into the ir available supply portfolio for this five -year drought scenario. More details on the SFPUC’s DRA can be found in Section 8.5 of their 2025 UWMP.
The percent reduction of average year supplies and projected deliveries from Valley Water during a five-year consecutive drought were estimated based on the projected shortages identified in Valley Water’s five-year drought analysis beginning in 2030 . Supply shortages are projected in the fourth and fifth years of the five-year drought period, which may result in reductions to the City’s supply allocation. For planning purposes, the City assumed Valley Water supply cutbacks proportional to the ratio of projected shortage to projected demand identified in Valley Water’ s multiple dry year analysis, as shown in Table 7-6.
Reductions in supplies associated with implementation of the Bay-Delta Plan were not included in this DRA because the timing of implementation remains uncertain . The Bay-Delta Plan is discussed in more detail in Section 7.1.3.
Table 7-6: Anticipated Percent Supply Reduction from Wholesale Suppliers Wholesale
Supplier 2026 2027 2028 2029 2030
Valley Water 0% 0% 0% 9% 6%
SFPUC 0% 0% 0% 0% 0%
The City’s groundwater supply is not expected to be limited by climate effects; as such, the City will consistently be able to pump groundwater up to the sustainable yield of 8,000 AFY.
Basis for Water Shortage Conditions
The City’s updated Water Shortage Contingency Plan ( WSCP) is detailed in Section 8.
Sunnyvale staff, in anticipation of 10 %, 20 %, 50%, and greater than 50% supply reductions , developed a water shortage contingency plan adopted in March of 1989, and most recently amended in June 2020, that includes mandatory (and voluntary) water use restrictions, rate block adjustment, and approaches for enforcement associated with each stage of anticipated reduction.
The WSCP amends the stages to correlate with the six stages prescribed by statute . The City initiates the stage based on the Assessment described in Section 8.2 which includes coordination with the wholesalers’ declaration of shortages and restrictions.
7.4.2 Water Source Reliability
Reliability of Treated Surface Water from SFPUC
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included in the Supply Assurance commitment and each has temporary and interruptible water supply contracts with San Francisco. Sunnyvale’s ISG is 14,100 AFY.
Tier 1 Drought Allocations
The WSA between the SFPUC and the wholesale customers, discussed previously in Section
6.1.1, includes as “Attachment H” a Water Shortage Allocation Plan (WSAP), also known as the Tier 1 Shortage Plan. This plan describes the method for allocating water from the RWS between the SFPUC’s retail customers, on the one hand, and the wholesale customers collectively, on the other, during system-wide shortages caused by drought. The Tier 1 Shortage Plan applies only when the SFPUC determines that a system -wide water shortage due to drought exists, as set forth in a declaration of water shortage emergenc y by the SFPUC; in the absence of such a declaration, the SFPUC also may opt to request voluntary cutbacks from its retail and wholesale customers to achieve water use reductions. The SFPUC and the wholesale customers most recently amended the Tier 1 Shortage Plan in 2025.
The SFPUC allocates water under the Tier 1 Shortage Plan when it determines that the projected available water supply is less than projected system -wide water purchases for the upcoming Supply Year, defined as the period from July 1 through June 30. The f ollowing table shows the retail customers’ share and the wholesale customers’ share of the annual water supply available during shortages depending on the level of system -wide reduction in water use that is required.
If the SFPUC determines that the level of system-wide reduction required during a shortage is greater than 20%, the SFPUC and the wholesale customers will meet to discuss the appropriate retail and wholesale customers’ shares of available water – also known as the retail and wholesale customers’ Tier 1 Allocations. The wholesale customers’ Tier 1 Allocation will be apportioned among the individual wholesale customers based on a separate methodology, known as the Tier 2 Drought Response Implementation Plan (Tier 2 Plan), which is separately ado pted by all the wholesale customers without the SFPUC’s involvement as discussed further below.
Table 7-7: SFPUC Tier 1 Drought Allocations
Level of System-Wide Reduction
in Water Use Required
Share of Available Water
SFPUC Retail Customers’ Share Wholesale Customers’ Share 5% or less
6% through 10%
11% through 15%
16% through 20%
35.5%
36.0%
37.0%
37.5%
64.5%
64.0%
63.0%
62.5%
The Tier 1 Shortage Plan allows for voluntary transfers of shortage allocations between the SFPUC and any wholesale customer as well as between wholesale customers themselves. In addition, voluntary transfers of water “banked” by the SFPUC or a wholesale customer, through reductions in usage greater than required, may occur.
Under the Tier 1 Shortage Plan if the retail customer s’ Tier 1 Allocation results in the retail customers receiving a “positive allocation” (i.e., a supply of additional water rather than a required reduction in water use), then the excess percentage for retail is re -allocated to the wholesale customers’ Tier 1 Allocation. The retail customers are also required to conserve a minimum of 5% for any level of reduction in system-wide water use. The additional water conserved by retail customers up to the minimum 5% level is deemed as remaining in RWS storage for inclusion in the calculation of projected available water in future successive dry years.
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The Tier 1 Shortage Plan will expire at the end of the term of the WSA in 2034, unless the SFPUC and the wholesale customers mutually agree to revise or terminate it prior to that date.
Tier 2 Drought Allocations
The wholesale customers have negotiated and adopted the Tier 2 Plan, referenced above, which allocates the wholesale customer Tier 1 Allocation from the Tier 1 Shortage Plan among each of the 26 wholesale customers. These Tier 2 Allocations are based on a formula that takes into account multiple factors for each wholesale customer including:
• Residential population;
• Non-residential “base” (i.e., indoor) use;
• Seasonal uses;
• Total RWS purchases in recent non-drought years; and
• ISG.
The Tier 2 Plan employs a structured, sequential, five -step method to allocate water to each wholesale customer. The allocations are constrained by minimum and maximum cutbacks, which establish the maximum final allocation and minimum guaranteed final allocation, respectively. No agency's final allocation can fall outside of these bounds. The allocation then pro ceeds by prioritizing indoor uses.
The subsequent steps systematically allocate the remaining available water based on different customer demands. First focusing on indoor demand, water is allocated based on an agency’s residential population and the State residential efficient indoor standard (47 gallons per person per day [gpcd] in 2025), followed by an allocation based on non -residential “base” (i.e., indoor) use. A limited amount of water is allocated based on seasonal use (e.g., cooling towers and irrigation). Finally, the remaining supply is allocated based on a weighted share of two -thirds RWS purchases in the recent non-drought years and one-third ISG.
The result of the Tier 2 Plan is each wholesale customers’ proportion, expressed as a percentage, of the available Tier 1 Allocation (Allocation Factor).
The Tier 2 Plan requires that the Allocation Factors be calculated by BAWSCA each year in preparation for a potential water shortage emergency. As the wholesale customers change their water use characteristics (e.g., increases or decreases in RWS purchases and use of other water sources, changes in monthly water use patterns, or changes in population), the Allocation Factor for each wholesale customer will also change. However, for long-term planning purposes, each wholesale customer may use as its Allocation Factor, the value identified in the Tier 2 Plan when adopted.
The Tier 2 Plan was renegotiated and adopted by all wholesale customers in 2025.
Reliability of Treated Surface Water from Valley Water
Current Valley Water supply and demand projections show anticipated supply shortages in the fourth and fifth years of a five -year drought period beginning in 2030 and 2045. Valley Water’s basic water supply strategy to compensate for supply variability is to store excess wet year supplies in the groundwater basin, local reservoirs, San Luis Reservoir, and/or Semitropic DRAFT
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Groundwater Bank, and draw on these reserve supplies during dry years to help meet demands.
These reserves, along with existing and planned future projects in the 2050 WSMP, help Valley Water meet demands during a prolonged drought . Current modeling incorporates projects identified in the 2050 WSMP to improve water supply reliability and to help meet increasing demands through 2045.
Reliability of Groundwater
The City’s water supply includes groundwater pumped from a conjunctively managed groundwater basin. The groundwater basins in Santa Clara County span nearly 400 square miles, with thousands of well users pumping groundwater for beneficial use . Protecting the local groundwater basins is critical to maintaining water supply reliability in the County of Santa Clara.
The City relies on Valley Water activities to maintain sustainable supplies, including managed groundwater recharge and in -lieu groundwater recharge (e.g., treated surface water deliveries, demand management programs, and SFPUC supply). Valley Water’s 2050 WSMP ensures that local groundwater resources are sustained and protected . Groundwater management encompasses activities and programs that identify and mitigate contamination threats to the groundwater basin, replenish and recharge groundwater supplies, prevent groundwater overdraft and land subsidence, and sustain storage reserves. Valley Water programs to sustain and protect groundwater resources are described in detail in the 2050 WSMP.
The allowable withdrawal of groundwater by the City depends on multiple factors, including withdrawals by other water agencies, the quantity of water recharged, and carry -over storage from the previous year. The City has six active wells that can produce up to 8,000 AF annually .
In the case of a drought, groundwater is expected to supplement purchased surface water from wholesalers to meet system demands.
Reliability of Recycled Water
Recycled water is not vulnerable to seasonal or climatic shortage . Therefore, recycled water is assumed to be a drought-proof water supply.
7.4.3 Total Water Supply and Use Comparison
The DRA total water supply and use comparison is presented in Table 7-8. The DRA evaluates the implementation of the WSCP shortage response actions for varying levels of water shortage based on the supply and demand projections and presents the estimated savings due to these actions.
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SECTION 7 – Water Supply Reliability and Drought Risk Assessment
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Table 7-8: Five-Year Drought Risk Assessment
2026 2027 2028 2029 2030
Gross water use 19,228 19,649 20,070 20,491 21,334
Total supplies 27,512 27,971 28,431 28,105 28,754
Surplus/(shortfall) w/o WSCP action 8,284 8,322 8,361 7,614 7,420 Planned WSCP actions (use reduction and supply augmentation) WSCP – use reduction savings benefit 0 0 0 0 0
WSCP – supply augmentation benefit 0 0 0 0 0
Revised surplus/(shortfall) 8,284 8,322 8,361 7,614 7,420 Resulting % use reduction from WSCP action 0% 0% 0% 0% 0% The DRA indicates that the City will be able to meet demands in the event of a five-year drought.
Although the results indicate no shortfalls, the City will work closely with SFPUC, Valley Water, and other water retail agencies to implement any stages of action to reduce the demand for water during water shortages. In the event of a decrease of local supplies, the City would respond by pursuing demand reduction programs (see SECTION 9) in accordance with the severity of the supply shortage. Any supply deficit would be compensated for by increased conservation levels and restrictions in consumption.
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2025 Urban Water Management Plan
SECTION 8 – Water Shortage Contingency Planning
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– WATER SHORTAGE CONTINGENCY PLANNING
A water shortage is defined as a case where the available water supply is insufficient to meet normally expected customer water use. A water shortage contingency plan (WSCP) is a detailed proposal for how a Supplier intends to act in the case of an actual water shortage condition. This plan is essential to a sound drought policy even if a Supplier appears to have low risk of water supply shortage conditions.
As required by §10632(a) of the Water Code, this chapter presents the City of Sunnyvale’s (City’s) WSCP including:
• A summary of the City’s water supply reliability analysis presented in Section 7 of the UWMP; • The City’s procedure for conducting and submitting its annual water supply and demand assessment;
• The legal authority that the City has for implementation and enforcement of its WSCP; • The water shortage levels of the WSCP and the demand reduction measures, supply augmentation measures, and/or operational changes implemented in each stage as it relates to the six stages required by the Water Code;
• The methods for monitoring and reporting a water shortage condition and water use reductions;
• The methods for ensuring compliance and enforcing demand reduction measures; • The protocols for communicating a water shortage condition and the measures implemented; • The financial consequences of implementing the WSCP and methods for mitigating revenue losses; and
• A summary of the WSCP adoption, submittal, and refinement procedures.
Each Supplier is required to adopt its WSCP as part of its Urban Water Management Plan (UWMP) and as a standalone document that can be refined and updated outside of the five-year UWMP planning cycle . For this reason, some information summarized in this chapter of the UWMP is duplicated from previous chapters for clarity such that the chapter can serve as a standalone document.
8.1 Water Supply Reliability Analysis
The analysis of water supply reliability assessment is based on three different analyses: annual, near-term (5 years), and long-term (20 years). The following summarizes the following analyses that were included in Sections 4, 6, and 7 of the UWMP:
• The methods for projecting water demands (Section 4), • The methods for projecting water supply (Section 6), and • The results of the water service reliability assessment (Section 7).
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SECTION 8 – Water Shortage Contingency Planning
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8.1.1 Demand Projections
The potable water use projections are based on the BAWSCA Regional Water Demand and Conservation Study, December 2025 (Demand Study). The Demand Study projections were developed using a hybrid water demand forecasting framework that integrates econometric modeling with conservation accounting tools. The econometric regression -based model (Econometric Model) links key drivers such as demographic growth, weather conditions, economic factors, and water rates to historical water use in order to estimate a his torical rate of use per driver. This rate was then used to estimate long-term projected water use. This approach generated monthly projections of baseline demand for the City that reflects structural drivers of water use. The model considered expected service area population and economic growth as well as passive conservation from plumbing codes and fixture turnover over time. Demand Study projections also account for potential effects of climate change. The full description of the Econometric Model and water demand forecasting framework is included in the Demand Study, attached as Appendix C of the UWMP. Projected additional water demand from planned new development and redevelopment within the City’s service area were added to the Demand Study projections.
Projected City potable and recycled (non -potable) water use is summarized by customer classification in Table 8-1. Because the City is largely built-out, it is expected that water use will continue to rise in future years primarily due to increasing population density.
Table 8-1: Projected Potable and Non-Potable Water Use by Customer Type (AFY) Customer Type Potable or Non-
Potable1 2030 2035 2040 2045
Single Family Residential Potable 5,323 5,254 5,231 5,209 Multi-Family Residential Potable 6,106 7,232 8,408 9,568 Commercial/Industrial (combined) Potable 4,933 6,241 7,086 7,910 Institutional Potable 315 398 452 505
Irrigation Potable 2,144 2,164 2,180 2,198
Other (Firelines) Potable 133 133 133 133
System Losses2 Potable 1,648 1,863 2,043 2,219
Commercial/Industrial (combined,
recycled water)
Non-Potable 95 119 142 165
Irrigation (recycled water) Non-Potable 637 794 950 1,107 Subtotal Potable3 20,602 23,285 25,533 27,743
Subtotal Non-Potable4 732 912 1,092 1,272
Total 21,334 24,197 26,625 29,015
Notes:
1. Non-potable use includes recycled water and any potable water added to the recycled water system.
2. Projected system losses are 8% of projected potable demand.
3. Projected potable water from the BAWSCA 2025 Demand Study with passive conservation categorized by customer use type and projected additional demand from planned new development and redevelopment within the City’s service area.
4. Water use within the City’s service area.
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SECTION 8 – Water Shortage Contingency Planning
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8.1.2 Supply Projections
The City relies on four water supply sources; surface water from San Francisco Public Utilities Commission (SFPUC), treated surface water from Santa Clara Valley Water District (Valley Water), groundwater, and recycled water. Surface water from the two wholesalers, SFPUC and Valley Water, provides most of the City’s water supply, averaging about 97% since 2015 . City owned- and operated-wells provide less than 1% and approximately 2% comes from recycled water. Since most of the City’s water supply is reli ant on SFPUC and Valley Water, the City is directly affected by the water supply conditions faced by each wholesaler.
SFPUC Supply
The City receives surface water from the City and County of San Francisco’s Regional Water System (RWS), operated by SFPUC . This supply is predominantly from the Tuolumne River watershed in the Sierra Nevada Mountains, delivered through the Hetch Hetchy aqueduct, but also includes treated water produced by SFPUC from local watersheds and facilities in Alameda and Santa Clara counties. The Alameda watershed, located in Alameda county, is designed to capture local runoff.
The amount of imported water available to SFPUC’s retail and wholesale customers is constrained by hydrology, physical facilities, and the institutional parameters that allocate the water supply of the Tuolumne River. Due to these constraints, SFPUC is dependent on reservoir storage to ensure ongoing water supply.
The business relationship between the SFPUC and its wholesale customers is largely defined by the “Water Supply Agreement between the City and County of San Francisco and Wholesale Customers in Alameda County, San Mateo County and Santa Clara County” (WSA) , effective since July 2009. This 25-year WSA replaced the Settlement Agreement and Master Water Sales Contract that expired in June 2009. The WSA addresses the rate-making methodology used by the SFPUC in setting wholesale water rates for its customers in addition to addressing water supply and water shortages for the RWS. The WSA, as amended and restated in 2025, describes the current contractual relationship between the SFPUC and the City.
The WSA is supplemented by an individual Water Supply Contract between SFPUC and each individual retailer, also active since July 2009. These contracts expire in 25 years. The City has an Individual Supply Guarantee (ISG) of 12.58 MGD (approximately 14,100 AFY). Although the WSA and accompanying Water Supply Contract expire in 2034, the ISG (which quantifies San Francisco’s obligation to supply water to its individual wholesale customers) surpasses their expiration and continues indefinitely . The City’s contract also includes a minimum purchase amount of 7.412 MGD (8,308 AFY), which Sunnyvale agrees to buy, regardless of whether sales drop below this level.
The WSA provides for a 184 MGD (expressed on an annual average basis) Supply Assurance to the SFPUC’s wholesale customers. This Assurance is subject to reduction, to the extent and for the period made necessary by reason of water shortage, due to drought, emergencies, or by scheduled RWS maintenance activities . The WSA does not guarantee that San Francisco will meet peak daily or hourly demands of SFPUC’s wholesale customers when their annual usage exceeds the Supply Assurance. The SFPUC’s wholesale customers have agreed to the allocation of the 184 MGD Supply Assurance among themselves, with each entity’s share of the Supply Assurance set forth on Attachment C to the WSA.
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Additional information regarding SFPUC supply reliability can be found below in the summary of SFPUC’s WSCP. For more detailed information, please refer to SPFUC’s current UWMP and/or WSCP.
Valley Water Supply
Valley Water supplies the City with treated surface water through an entitlement of imported water that is Delta-conveyed from the Central Valley Project (CVP) and State Water Project (SWP), as well as surface water from local reservoirs. The City has a 7 0-year contractual agreement with Valley Water, effective 1981 to 2051.
Valley Water’s imported water is conveyed through the Sacramento -San Joaquin Delta and pumped and delivered to the county through three main pipelines: the South Bay Aqueduct, which carries water from the SWP, and the Santa Clara Conduit and Pacheco Condui t, which convey water from the Federal CVP. More than 70% of this supply is delivered to treatment plants, about 15% is diverted upstream by the SFPUC and delivered to cities in northern Santa Clara County, and almost 15% is used for recharge. Any excess Delta-conveyed supplies are stored in the Semitropic Groundwater Bank in San Joaquin Valley for later use, such as withdrawal during dry periods. Valley Water can also store imported water supplies locally in the Anderson and Calero Reservoirs; however, the Anderson Reservoir is currently drained down due to seismic concerns.
Valley Water is working on rebuilding the dam, with completion expected by the end of 2033 (2050 WSMP, 2025).
Local runoff is captured in local reservoirs for recharge into the groundwater basin or treatment at one of Valley Water’s three water treatment plants. The total storage capacity of the ten Valley Water operated reservoirs in Santa Clara County is approximately 166,000 AF, however, several reservoirs are operating at restricted capacity due to seismic stability concerns. Local water captured in local reservoirs and natural groundwater recharge provides up to 30% of Santa Clara County’s water supply. Res ervoir operations are coordinated with imported Bay -Delta water received from the SWP and the CVP.
Valley Water has a contract for 100,000 AFY from the SWP and 152,500 AFY from the CVP.
However, the actual amount of water delivered is typically less than these contractual amounts and depends on hydrology, conveyance limitations, and environmental regulations. Valley Water expects average allocations of Delta -conveyed water to generally decline over time due to impacts of climate change, potential environmental regulations affecting the Sacramento –San Joaquin Delta, and State mandates to reduce reliance on the Delta (2050 WSMP, 2025).
However, over the years, Valley Water has attempted to sustain overall existing supplies by participating in projects that would offset the predicted decline of Delta-conveyed imported water supplies. In October 2019, Valley Water vote d to support the Delta Conveyance Project, which is a proposed plan to improve the infrastructure that conveys water through the Sacramento-San Joaquin Delta. This plan would potentially provide on average 14,000 AFY of imported water supply benefits to Valley Water (2050 WSMP, 2025).
Valley Water has also been evaluating water reuse opportunities, including potable reuse, as a reliable, locally controlled supply that can mitigate drought risks and further diversify its water supply portfolio. In October 2024, the State enacted the Direct Potable Reuse (DPR) regulations, enabling water supply agencies to pursue a new and more flexible approach to potable reuse.
Valley Water aims to develop 24,000 AFY of potable reuse by 2035, with a long -term vision of expanding water reuse in the county to up to 32,000 AFY by 2050.
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For more detailed information regarding Valley Water’s supply reliability, please refer to Valley Water’s current UWMP and/or WSCP.
Groundwater
The City owns and operates six active wells and one well on stand -by for emergencies .
Groundwater makes up a small percentage of the City’s total water supply and is used to supplement imported SFPUC and Valley Water supply.
Valley Water manages the groundwater basin and provides county -wide groundwater and conservation planning assistance. Local groundwater supplies represent up to half of the county’s water supply during normal years and are crucial to the region’s future w ater supply reliability.
Valley Water uses conjunctive use management, a practice by which the groundwater basin is pumped more in drier years and then replenished (or recharged) during wet and average years, to ensure the sustainability of groundwater ba sins. Groundwater is replenished naturally from rainfall and augmented by Valley Water-operated recharge. Conjunctive use helps to protect the groundwater basin from overdraft, land subsidence, and saltwater intrusion, and provides critical groundwater storage reserves.
Recycled Water
The City’s current recycled water system consists of the Recycled Water Pump Station located at the WPCP, the Sunnyvale Golf Course pump station, the San Lucar Tank and Pump Station, the Wolfe Road Pump Station (WRPS), and approximately 22 miles of recycled water pipelines ranging in diameter from 6- to 36-inches. The WRPS was completed in 2018 as part of the Wolfe Road Pipeline Extension Project, which added approximately 13,000 feet of pipeline to extend the recycled water system along Wolfe Road, reaching the Apple® Campus 2. Both the WRPS and the pipeline extension are owned by Valley Water and maintained by the City’s Water and Sewer Services Division. In 2018, the City completed a Capital Improvement Project to facilitate parallel production of recycled water and NPDES discharge, thereby providing enhanced production and delivery reliability.
The City’s 2024 Recycled Water Master Plan Update (RWMPU) details the City’s existing recycled water demands and infrastructure and evaluates potential customer demands and proposed infrastructure through desktop analyses and hydraulic modeling. The RWMPU is detailed further in Section 6.4.5 of the UWMP.
In 2023, California State Legislature enacted AB 1572, which prohibits the use of potable water to irrigate non -functional turf on certain properties beginning in 2027. This policy change may encourage both existing customers and new developments to use recycled water to irrigate non- functional turf areas.
Impacts of Climate Change
The region is subject to growing water supply challenges concerning climate change, including recurring droughts and increased demand from population growth. The City’s potable water is primarily supplied by SFPUC and Valley Water; as such, the City relie s on each wholesaler to address the effects of climate change in their long -term planning efforts. Valley Water released the 2050 Water Supply Master Plan (2050 WSMP, https://fta.valleywater.org/dl/RQWqGqbX3rrk) in 2025, which includes a discussion on the effects of climate change on water supply reliability.
The SFPUC, in partnership with The Water Research Foundation, developed the Long Term DRAFT
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Vulnerability Assessment (LTVA, https://www.sfpuc.gov/about-us/reports/long-term-vulnerability- assessment) of the RWS, which was completed in 2021 and amended in 2024. The LTVA evaluates how climate change could impact the RWS through 2070 by assessing the potential impacts of increases in temperature and changes in precipitation. Additional detail on how climate change impacts were incorporated in to wholesaler supply projections can be found in each wholesaler’s respective UWMP.
Supply projections for the City’s four sources of potable and non -potable water provide a basis for assessing water supply reliability. The breakdown of total supply by source was determined using the City’s contractual agreements with each wholesaler, pr ojected demands provided to each wholesaler, and historical production trends . Projected water supply is listed by source in Table 8-2.
Table 8-2: Water Supplies – Projected (AFY)
Water Supply Additional Detail
on Water Supply
Potable or
Non-Potable 2030 2035 2040 2045
Purchased Water1 SFPUC Potable 12,008 12,490 13,389 14,091 Purchased Water2 Valley Water Potable 9,341 11,222 11,928 12,163 Groundwater3 Wells Potable 8,000 8,000 8,000 8,000
Recycled Water Recycled Water Non-Potable 732 912 1,092 1,272 Subtotal Potable 29,349 31,712 33,317 34,254
Subtotal Non-Potable 732 912 1,092 1,272
Total2 30,081 32,624 34,409 35,526
Notes:
1. Total available supply from SFPUC is equal to the City’s ISG of approximately 14,100 AFY; however, for planning purposes, the reasonably available volume presented herein reflects the projections provided to SFPUC based on the City’s projected demand and the availability of other supplies.
2. The projections provided herein reflect projections provided to Valley Water based on the City’s projected demand and availability of other supplies. The City can purchase additional available water from Valley Water during non- dry years when water is available.
3. Although the City has on average pumped about 138 AF annually, the total safe yield of groundwater is 8,000 AFY.
In the event of a decrease in wholesaler supplies, the City would increase the use of groundwater supplies and respond by pursuing demand reduction programs in accordance with the severity of the supply shortage . Any supply deficit would be compensated for by increased groundwater supply, conservation levels, and restrictions in consumption.
8.1.3 Water Supply Reliability Assessment
The water service reliability assessment requires the comparison of supply and demand projections for three scenarios:
• Normal year,
• Single dry year, and
• Five consecutive dry years.
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The percent of total annual supply available for each scenario is based on the historical hydrology identified by Valley Water and cutbacks determined by the City’s wholesalers (Appendix H). The City has elected to use the base years used by Valley Water for consistency, since groundwater managed by Valley Water will be relied upon to make up any deficit from water wholesalers .
Because allowable groundwater pumping is based only on the sustainable yield, groundwater supply availability is not expected to decrease during dry years. Additionally, recycled water is not dependent on climatic effects and is assumed to be unaffected by any drought conditions .
Table 8-3 presents the base years for each of the three conditions described above.
Table 8-3: Basis of Water Year Data
Year Type Base Year1
Average Year 1922-2021
Single-Dry Year 1977
Five Consecutive Dry Years 1st Year 1988
Five Consecutive Dry Years 2nd Year 1989
Five Consecutive Dry Years 3rd Year 1990
Five Consecutive Dry Years 4th Year 1991
Five Consecutive Dry Years 5th Year 1992
Note:
1. All base years are consistent with Valley Water.
Using the water supply and demand projections and the portion of supplies available during normal year, single dry year, and five consecutive dry year conditions, this section presents the comparison between projected supply and projected demand for each c ondition in five -year increments through 2045.
The reliability analysis assumes reduced supply from SFPUC from the implementation of the amendments to the Water Quality Control Plan for the Bay -Delta Plan (Bay -Delta Plan Amendment) described in Section 7.1.3 of the UWMP and detailed further in the SFPUC’s UWMP. The Bay-Delta Plan would require 30-50% unimpaired flow; however, because the plan is currently in negotiation, the timing and requirements of implementation remains uncertain. For the purposes of the 2025 UWMP analysis, the SFPUC assumed implementation beginning in 2030.
The SFPUC conducted an analysis of the RWS supply reliability under both conditions, with and without 40% unimpaired flow. The SFPUC also modeled two separate cutback scenarios: one based on the actual projected wholesale demands through 2045 and another scenario based on the wholesale contract amount of 184 MGD. The City is reporting the more conservative modeled scenario based on Bay-Delta Plan Amendment implementation in 2030 and projected demands for consistency with the SFPUC UWMP; however, the SFPUC has acknowledged the contractual obligation to supply 184 MGD to the wholesale customers during non-drought years and thus has retained the second modeled scenario for planning purposes.
The supply reliability analysis also considered potential cutbacks to Valley Water supply during dry years. Valley Water indicated in their 2025 UWMP that with existing and planned projects’ supplies, Valley Water’s diverse water supplies are sufficient to meet demands throughout the first three-year period in a five-year drought in all demand years without havi ng to call for short- term water use reductions. However, supply shortages are projected in the fourth and fifth years DRAFT
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of a five-year drought period beginning in 2030 and 2045, which may result in reductions to the City’s supply allocation. For planning purposes and for a more conservative approach, the City assumed Valley Water supply cutbacks proportional to the ratio of projected shortage to projected demand identified in Valley Water’s multiple dry year analysis. Additional detail on Valley Water’s multiple dry year analysis can be found in Valley Water’s most current WSCP and UWMP. Table 8-4 presents the service supply reliability assessment for each condition.
Table 8-4: Water Service Reliability Supply and Demand Comparison 2030 2035 2040 2045
Normal Year
Supply Totals 30,081 32,624 34,409 35,526
Demand Totals 21,334 24,197 26,625 29,015
Surplus/(shortfall) 8,747 8,427 7,784 6,511
% Shortage 0% 0% 0% 0%
Single Dry Year
Supply Totals 26,340 28,499 29,697 30,333
Demand Totals 21,334 24,197 26,625 29,015
Surplus/(shortfall) 5,006 4,302 3,072 1,318
% Shortage 0% 0% 0% 0%
Five Consecutive Dry Years
First
Year
Supply Totals 26,340 28,499 29,697 30,333
Demand Totals 21,334 24,197 26,625 29,015
Surplus/(shortfall) 5,006 4,302 3,072 1,318
% Shortage 0% 0% 0% 0%
Second
Year
Supply Totals 25,013 27,262 28,373 28,935
Demand Totals 21,334 24,197 26,625 29,015
Surplus/(shortfall) 3,679 3,065 1,748 (80)
% Shortage 0% 0% 0% 0.3%
Third
Year
Supply Totals 25,013 27,262 28,373 28,935
Demand Totals 21,334 24,197 26,625 29,015
Surplus/(shortfall) 3,679 3,065 1,748 (80)
% Shortage 0% 0% 0% 0.3%
Fourth
Year
Supply Totals 24,192 27,262 28,373 27,977
Demand Totals 21,334 24,197 26,625 29,015
Surplus/(shortfall) 2,858 3,065 1,748 (1,039)
% Shortage 0% 0% 0% 3.6%
Fifth
Year
Supply Totals 24,419 27,262 28,373 28,272
Demand Totals 21,334 24,197 26,625 29,015
Surplus/(shortfall) 3,085 3,065 1,748 (744)
% Shortage 0% 0% 0% 2.6%
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Given the supply and demand comparison presented in Table 8-4, the results of the supply reliability assessment can be summarized as follows:
• Normal Year – The City can anticipate meeting all water demands through 2045 under normal year supply conditions given the stated assumptions.
• Single Dry Year – The City can anticipate meeting all water demands through 2045 under single dry year supply conditions given the stated assumptions. • Five Consecutive Dry Years – The City can anticipate meeting all water demands through 2040 under consecutive five dry -year supply conditions given the stated assumptions. The City anticipates shortfalls only up to 4% from the second to fifth year of a five -year drought period beginning in 2045.
As shown in the tables above, Sunnyvale would be able to increase the amount of groundwater pumped to offset anticipated deficiencies from other sources. The Sunnyvale groundwater basin is not adjudicated, which means the right to pump groundwater from the basin has not been given by judgment of a court or board.
For each of the five -year increments presented above, the five -year dry period indicates that supplies will be able to meet demands out to 2040 through increased groundwater pumping and implementation of drought conservation programs . Since t he projected shortfalls anticipated during a multi-year drought in 2045 do not exceed 4% of projected demand, the City will be able to address any supply deficiency with minimal rationing.
8.1.4 Drought Risk Assessment
For the near-term water supply reliability, the DRA requires the analysis of five consecutive dry years beginning in 2026 including the consideration of climate change effects and any potential regulatory or other locally applicable conditions in conjunction with WSCP implementation . For this assessment, the same procedures described above were used to develop supply and demand projections for the next five years (2026-2030).
The DRA total water supply and use comparison is presented in Table 8-5.
Table 8-5: Five-Year Drought Risk Assessment
2026 2027 2028 2029 2030
Gross water use 19,228 19,649 20,070 20,491 21,334
Total supplies 27,512 27,971 28,431 28,105 28,754
Surplus/shortfall w/o WSCP action 8,285 8,322 8,360 7,614 7,421 Planned WSCP actions (use reduction and supply augmentation) WSCP – use reduction savings benefit 0 0 0 0 0
WSCP – supply augmentation benefit 0 0 0 0 0
Revised surplus/(shortfall) 8,285 8,322 8,360 7,614 7,421 Resulting % use reduction from
WSCP action 0% 0% 0% 0% 0%
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The DRA indicates that the City will be able to meet demands in the event of a five-year drought.
Although the results indicate no shortfalls, the City will work closely with SFPUC, Valley Water, and other water retail agencies to implement any stages of action to reduce the demand for water during water shortages. In the event of a decrease of local supplies, the City would respond by pursuing demand reduction programs (see Section 9) in accordance with the severity of the supply shortage. Any supply deficit would be compensated for by increased conservation levels and restrictions in consumption.
8.2 Annual Water Supply and Demand Assessment Procedures In accordance with Water Code §10632.1, every Supplier is required to conduct an annual water supply and demand assessment (Assessment) and submit an Assessment Report to DWR on or before July 1st of each year. The purpose of the Assessment is to evaluate the reliability of the water supplier’s water supply system on a short-term basis. This will aid the Supplier in identifying near-term (yearly or monthly) water shortages and implement the appropriate shortage response actions as laid out in the WSCP . The Assessment will also allow the City to determine the effectiveness of the WSCP and update the plan accordingly.
The Assessment will be based on the previous year’s available supply and measured demand .
First, the anticipated unconstrained demand for the current year will be developed . Then, any anticipated climatic variations, population growth, demographic changes, current and/or proposed development, State or local regulations, and existing infrastructure capabilities will be considered in altering the unconstrained demand. Considering each of these factors and how they may affect anticipated supply and/or deman d, a supply and demand comparison will be completed for the current year under normal hydrologic conditions and under dry conditions . This comparison will allow the City to identify any potential water shortages and obtain City Council approval to activate the appropriate WSCP stage.
8.2.1 Decision-Making Process
On an annual basis, the Water and Sewer Division (Division) of the City will perform the Assessment once data has been received from the wholesalers, SFPUC and Valley Water, in mid-April. The wholesalers will inform the City if they will be able to meet w ater supply commitments for the City or if they will be requesting voluntary or mandatory reductions. If the projected unconstrained demands can be met by the City, then approval of the Assessment by City Council will not be required. When water supply s hortfalls trigger the need for demand reduction, then approval of the Assessment by City Council shall be obtained no later than May 31st. City Council approval of the Assessment, which shall include the recommended stage for cutbacks as described in Section 8.3 below, will allow implementation of the recommended stage and no additional approval shall be required. Removal or elevation of the stages will require City Council approval.
For example, data from wholesalers for Fiscal Year (FY) 2026-2027 will be received by April 15, 2026. The Assessment will be prepared by the Division to determine if the supply for the projected demand for FY 2026 -2027 will trigger the need for shortage r esponse actions as identified in Section 8.3. Stages 1 – 6 will require City Council approval by May 31, 2026 for it to be effective by July 1, 2026 through June 30, 2027. The Assessment Report will be finalized and submitted to DWR on or before July 1st on an annual basis.
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8.2.2 Data and Methodology
The methodology that will be used by the City to determine water demands for the Assessment year includes projecting demands based on historical post-drought recovery considering factors such as economic growth and new developments , rate increases, conservation activity, climate change, any global and regional events, and population density. Demand data available at the time of Assessment preparation will be used to calibrate, evaluate, and accurately estimate the demands for the Assessment year under normal and dry hydrological conditions.
Unconstrained demand is water demand absent any water supply and demand restrictions. The following methodology will be used in estimating the Assessment year’s unconstrained demand:
1. Identify the most recent 12-month period in which no supply shortages or demand restrictions were put in place.
2. Collect monthly water billing data for the period selected in Step 1.
3. Identify factors that may have influenced water demand, such as weather and economy, and apply adjustments as appropriate.
Supply data from Valley Water and SFPUC will also be used to determine the reliability of the water supply system. The City will use the projected demand and supplies to assess whether shortfalls will exist under normal and dry hydrological conditions due to unanticipated changes not projected in the 2025 UWMP. The shortfalls will be quantified and correlated with the appropriate WSCP stages to identify the shortage level response action that will be triggered to offset the shortage in water supplies and determine if other actions are necessary (i.e., increase groundwater pumping or other water conservation measures).
Using the report template developed for the purposes of this Assessment, the City will draft a report presenting the data available and detailing the processes used to project the supplies and demands for the Assessment year and complete the analysis . The report will identify any anticipated water supply shortfalls and the corresponding WSCP stage along with any WSCP actions proposed to mitigate the supply shortfalls. This report will be presented at a City Council meeting in or before June of each year i f implementation of a WSCP stage is required and any WSCP actions will be implemented beginning by or before July. The report will then be submitted to DWR no later than July 1st.
Based on the processes described above, Table 8-6 presents the timeline the City will adhere to for the process of completing the annual Assessment and submitting the Assessment Report.
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Attachment 1
City of Sunnyvale
2025 Urban Water Management Plan
SECTION 8 – Water Shortage Contingency Planning
www.hydroscience.com
Table 8-6: Assessment Completion Timeline
Month Activities Completed By
February Obtain monthly water use data by customer type from Finance Department for previous year.
Water and Sewer
Division
February Determine monthly water production data (surface water, potable groundwater, recycled water) for previous year.
Water and Sewer
Division
February Obtain population estimates for previous year from DOF (https://www.dof.ca.gov/Forecasting/Demographics/Estimates/).
Water and Sewer
Division
March Complete analysis for previous year (supply and demand comparison, hydrologic and regulatory conditions, infrastructure constraints, etc.).
Water and Sewer
Division
March
Calculate projected unconstrained demand for current year and identify/describe projection methods (projected population growth, etc.).
Water and Sewer
Division
April
Identify projected hydrologic conditions for current year and obtain any anticipated surface water supply constraints from wholesalers for current year.
Water and Sewer
Division
April Determine current conditions of groundwater supply and groundwater table to anticipate any groundwater supply constraints for current year.
Water and Sewer
Division
April
Complete analysis for current year based on a “dry year.” Determine the anticipated monthly water supply reliability for the current year using calculation spreadsheet.
Water and Sewer
Division
April
Determine if/when water supply shortages will occur and what WSCP stage the shortage will fall into. Determine what (if any) WSCP actions will need to be implemented to mitigate supply shortage.
Water and Sewer
Division
May Prepare Assessment Report presenting the findings of the Assessment and WSCP actions to be implemented.
Water and Sewer
Division
May/ June Present findings and Assessment Report to City Council. Water and Sewer Division
by July Implement the WSCP actions as approved by City Council. Water and Sewer Division
July Submit final Assessment Report to DWR by July 1st. Water and Sewer Division
Note: Months are approximate and can be adjusted as needed.
8.3 Standard Water Shortage Stages
In response to the severe drought of 2012 -2016, legislation in 2018 created a WSCP mandate replacing the water shortage contingency analysis under former law. Suppliers are authorized to continue using their own water shortage levels that may have been included in past WSCPs provided the Supplier includes a narrative or graphic describing the Supplier’s water shortage levels in relationship to the six standard water shortage levels prescribed by statute - six standard water shortage levels corresponding to progressive ranges of up to 10%, 20%, 30%, 40%, 50%, and greater than 50% shortage.
This section provides a general description of the WSCP for each of the water wholesalers and a detailed description of the City’s water shortage stages . For more information regarding each wholesaler’s response to water shortage, please refer to the wholesaler’s most current WSCP.
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Attachment 1
City of Sunnyvale
2025 Urban Water Management Plan
SECTION 8 – Water Shortage Contingency Planning
www.hydroscience.com
8.3.1 SFPUC Water Shortage Allocation Plan
The WSA between the SFPUC and the wholesale customers, discussed previously in Section
8.1.2, includes as “Attachment H” a Water Shortage Allocation Plan (WSAP), also known as the Tier 1 Shortage Plan. This plan describes the method for allocating water from the RWS between the SFPUC’s retail customers, on the one hand, and the wholesale customers collectively, on the other, during system -wide shortages caused by drought. The WSAP identifies the retail customers’ and wholesale customers’ respective shares of the annual water supply available during shortages that require system -wide reductions in water use of 20% or less. These percentage shares, referred to as the retail customers’ Tier 1 Allocation and the wholesale customers’ Tier 1 Allocation, are shown in the first four rows of Table 8-7 (Shortage Levels 1 and 2). For example, when the required level of system-wide reduction in water use is 6 to 10%, the retail customer Tier 1 Allocation is 36% of the annual water supply available, and the wholesale customer Tier 1 Allocation is 64% of the annual water supply available. Under the WSAP, if the retail customers’ Tier 1 Allocation results in the retail customers having a “positive” allocation (i.e., a supply of additional water rather than a required percentage reduction in water use), then the retail customers’ percentage share of the available water supply would be reduced to eliminate any positive allocation to retail customers, with a corresponding increase in the percentage share of the available water supply allocated to the wholesale customers. For any level of required reduction in system -wide water use, the SFPUC shall require retail customers to conserve a minimum of 5%, with any resulting reallocated supply credited to storage for inclusion in the calculation of projected available RWS water supply in a subsequent year. Table 8-7 includes a cross-reference relating the existing WSAP levels of system -wide water use reduction to the six standard water shortage levels, consistent with California Water Code Section 10632(3)(b). The WSAP does not define Tier 1 Allocations for the retail customers and the wholesale customers for system-wide shortages requiring greater than a 20% reduction in water use. For the purposes of this WSCP, the SFPUC assumes that the Tier 1 Allocations for the 16-20% reduction in water use level (37.5% for retail and 62.5% for wholesale) would apply to all higher shortage levels. In practice, the WSAP defines a process for the SFPUC and the wholesale customers to determine whether the application of thos e Tier 1 Allocations to shortage levels greater than 20% is appropriate or whether a change is required (for further information about this process, see Appendix D of SFPUC’s most recent WSCP).
The WSAP also implements a method for allocating the wholesale customers’ Tier 1 Allocation among the respective wholesale customers, known as the “Tier 2 Drought Response Implementation Plan,” which has separately been adopted by the wholesale customers and does not include the SFPUC. The SFPUC’s shortage response actions as they relate to the wholesale customers are defined in the WSAP and are included in this WSCP by reference.
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Attachment 1
City of Sunnyvale
2025 Urban Water Management Plan
SECTION 8 – Water Shortage Contingency Planning
www.hydroscience.com
Table 8-7: SFPUC Retail and Wholesale RWS Allocations during System-wide Shortage Shortage Level
Required Level of
System-wide Reduction
in Water Use
SFPUC Retail Share of
Available RWS Supply1
Collective Wholesale
Customers’ Share of
Available RWS Supply
1 5% or less 35.5% 64.5%
1 6 – 10% 36.0% 64.0%
2 11 – 15% 37.0% 63.0%
2 16 – 20% 37.5% 62.5%
32 Up to 30% 37.5% 62.5%
42 Up to 40% 37.5% 62.5%
52 Up to 50% 37.5% 62.5%
62 >50% 37.5% 62.5%
Notes:
1. While Groveland CSD is reported in the SFPUC UWMP as a wholesale customer, it is not a party to the WSA, and it is considered a retail customer of the SFPUC for the purpose of allocating RWS supplies between retail and wholesale customers under the WSAP. Thus, RWS supplies to Groveland CSD are accounted for in the retail supply allocation.
2. The WSAP does not define supply allocations for the retail Customers and the wholesale Customers for system- wide shortages requiring greater than a 20% reduction in water use. Instead, the WSAP sets forth a process for the SFPUC and the wholesale customers to determine whether the application of the allocations for the 16 -20% reduction in water use level to shortage levels greater than 20% is appropriate or whether a change is required.
8.3.2 Valley Water’s Water Shortage Contingency Plan
Valley Water’s basic water supply strategy to compensate for supply variability is to store excess wet year supplies in the groundwater subbasins, local reservoirs, San Luis Reservoir, and Semitropic Groundwater Bank, then to draw on these stored supplies during dry years to help meet demands. Based on projected demands, and Valley Water’s existing and planned sources of supply, Valley Water will be able to meet countywide demands through 2050 under normal and single dry conditions. Under five consecutive dry year conditions, Valley Water’s diverse water supplies are sufficient to meet demands throughout the full five -year drought in demand years 2035 and 2040, but there will be small shortages (less than 10%) in the last two years of the drought in demand years 2030 and 2045. Those shortages will be addressed through the combination of supply augmentation from transfer and exchange and water use reductions.
The DRA indicates that if a five -year drought were to occur under existing conditions, Valley Water’s existing supply is sufficient to meet expected demands for the first three years. During the last two years of this near -term drought, however, estimates of projected water supply and use reveal that there could be a possible shortfall of 14,600 AF in 2029 and 25,000 AF in 2030.
The shortfall is largely attributed to assumed low imported water supply as occurred during the two most recent severe droughts in the last 10 years. If such shortfalls were to happen, Valley Water will implement its WSCP actions including calling for water use reduction and augmenting supplies with supplemental sources such as water transfers and exchanges, to meet potential shortage.
Valley Water uses six stages to categorize its water supply shortage, outlined in Table 8-8. Valley Water’s shortage levels are determined based on projected end-of-year groundwater storage and surface water (imported and local) availability. The shortage stages also include catastrophic interruption of water supplies due to earthquakes and other emergency events.
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Attachment 1
City of Sunnyvale
2025 Urban Water Management Plan
SECTION 8 – Water Shortage Contingency Planning
www.hydroscience.com
Table 8-8: Valley Water’s WSCP Six Standard Shortage Stages Shortage Level/Stage Stage Title Water Shortage
1 Alert ≤ 10%
2 Warning 10-20%
3 Severe 20-30%
4 Critical 30-40%
5 Extreme 40-50%
6 Emergency > 50%
• Stage 1 is the alert stage that is meant to warn the public that current water use is tapping groundwater reserves. This stage is triggered when local groundwater and/or reservoir storage is projected to drop below normal stage and/or surface water supplies are reduced. • Stage 2 is the warning stage. Shortage conditions continue to progress, requiring the initiation of drought response actions and close coordination with retailers and cities to encourage enacting of water use restrictions.
• Stage 3 is the severe stage. Shortage conditions are worsening, requiring close coordination with retailers and cities to encourage increase of enforcement activities. • Stage 4 represents critical conditions. This is typically the most severe stage in a multi -year drought. This stage is triggered when groundwater storage and expected surface water deliveries are projected to fall below the lower threshold of Stage 3. • Stage 5 and 6 are for extreme and emergency situations. These stages are meant to address an immediate crisis such as a major infrastructure failure when water supply may only be available to meet health and safety needs. Stage 5 or 6 can also be trigger ed in a deep drought when groundwater basin and reservoir storage levels are projected to be dangerously low.
Valley Water’s WSCP establishes procedures for shortage levels, the actual implementation of a water level, however, needs to consider additional factors, including proactively declaring a shortage to allow time for behavior changes to achieve water use re duction, customer response to the current level, and available response actions.
During droughts or shortages, Valley Water considers all available tools to minimize their impact.
Valley Water’s shortage response actions broadly fall into four categories – supply augmentation, demand reduction, operational changes, and mandatory prohi bitions against specific water use practices.
Valley Water’s LOS goal is to meet 100% demand during normal years and at least 80% demand during droughts. Valley Water’s drought response actions aim to achieve this service goal and minimize shortage impacts on the community. Based on lessons learned from the 2012 -2016 and 2020-2022 droughts, Valley Water updated the actions that it may take in response to a declaration of a water shortage. Table 8-9 provides a summary of Valley Water’s shortage response actions for each stage. Because each drought is different, it is important to keep flexibility within each drought stage for when to implement each drought response action. This allows Valley Water to identify and implement the actions that will provide the most benefit for the specific drought conditions. The determination of specific actions at each shortage level will be based on the evaluation of cost, timing, supply availability, storage conditions, and other factors.
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Attachment 1
City of Sunnyvale
2025 Urban Water Management Plan
SECTION 8 – Water Shortage Contingency Planning
www.hydroscience.com
Table 8-9: Water Shortage Response Actions
Stage Water Shortage Response Actions
1 – Alert ≤10% • 0–10% from demand reduction
• 0–10% met by Storage
2 – Warning 10–20% • 0–20% from demand reduction
• 0–20% met by Storage
• Supply augmentation
• Operational changes
3 – Severe 20–30% • 0–20% from demand reduction
• 0–30% met by Storage
• Supply augmentation
• Operational changes
4 – Critical 30–40% • 0–20% from demand reduction
• 0–40% met by Storage
• Supply augmentation
• Operational changes
5 – Extreme 40–50% • ≥20% from demand reduction
• 0–50% met by Storage
• Supply augmentation
• Operational changes
6 – Emergency >50% • ≥20% from demand reduction
• 0–50% met by Storage
• Supply augmentation
• Operational changes
Factors Impacting Supply Reliability
Many factors and events affect Valley Water’s water supply availability in any given year. To evaluate water supply conditions each year, Valley Water uses information on anticipated CVP and SWP allocations for imported supply, precipitation in local wate rsheds to estimate reservoir inflow and natural groundwater recharge, and groundwater storage for groundwater availability.
In addition, the determination of projected available water supply also considers supplies from SFPUC, carryover storage, and out-of-county storage.
Valley Water’s many supply sources are subject to hydrologic variability and additional constraints including regulatory and permit constraints, seismic threats to the Delta levee system, and infrastructure capacities. A summary of all constraints to Valley Water’s water supply sources is provided in more detail in Valley Water’s UWMP.
8.3.3 Sunnyvale’s Shortage Stages of Action
Sunnyvale staff, in anticipation of 10 %, 20 %, 50%, and greater than 50% supply reductions , developed a WSCP adopted in March of 1989 that includes mandatory (and voluntary) water use restrictions, rate block adjustment, and approaches for enforcement associated with each stage of anticipated reduction . The City’s WSCP was most recently amended in June 2020, with changes including updating the previous stages to correlate with the six stages prescribed by statue.
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Attachment 1
City of Sunnyvale
2025 Urban Water Management Plan
SECTION 8 – Water Shortage Contingency Planning
www.hydroscience.com
The following Table 8-10 describes the six standard water shortage levels. The City initiates the stage based on the Assessment as described in Section 8.2 which includes coordination with the wholesalers’ declaration of shortages and restrictions.
Table 8-10: Water Shortage Contingency Plan Levels
Shortage
Level/Stage
% Shortage
Range
Shortage
Condition
Shortage Response Actions Summary
1 ≤ 10% Alert
• Increase public information campaigning
• Increase educational programs
• Reduce system flushing
2 10-20% Moderate
• Increase water waste patrols and enforcement of permanent water use restrictions
• Restrict landscape irrigation to certain days
3 20-30% Severe
• Additional restrictions on outdoor and non-essential water use • Drought surcharges and increased rates
• Flow restrictors
• Increase production monitoring
4 30-40% Critical
• Additional restrictions on outdoor and non-essential water use • Allocations and mandatory conservation
• Restrict use of decorative fountains and filling/refilling swimming pools
• No new swimming pool or pond construction or installation of new lawns
5 40-50% Catastrophic
• Additional restrictions on outdoor and non-essential water use • Moratorium or net zero demand increase on new connections • Restrict irrigation to certain months
6 > 50% Catastrophic • Additional restrictions on outdoor and non-essential water use • Increase use of non-potable water
8.4 Shortage Response Actions
The Water Code requires documentation of the specific actions to be undertaken during a water shortage. The City has developed a set of demand reduction measures, as well as supply augmentation options and operational changes, to be undertaken in response to each shortage level identified in Table 8-10. The WSCP information presented herein is based on the City’s response to the 2012-2016 and 2021-2023 drought conditions and can be updated, as necessary.
City Council must approve the activation of the City’s WSCP, and it is prepared to act in a timely manner to impose any water use restrictions and regulations deemed necessary in a water supply shortage emergency. Before imposing mandatory water use restrictions, the water shortage would be assessed based on the relative severity of the current drought/water shortage condition and the implementation of any State mandated water use cutbacks. A water shortage level would be recommended by the Environmental Services Director and approved by the City Council based on the levels listed in Table 8-10, and a water shortage declaration would be issued by the City Council. City Council would then determine the overall strategy and specific mix of voluntary and mandatory water consumption reduction measures to be implemented . Customers would be notified in accordance with standard Brown Act notification requirements . Customer and public notification methods that the City may employ in the event of a current or anticipated water shortage include, but are not limited to:
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City of Sunnyvale
2025 Urban Water Management Plan
SECTION 8 – Water Shortage Contingency Planning
www.hydroscience.com
• Posts on the City’s website,
• Social media posts,
• Bill stuffers or flyers, and
• Press releases.
Additional detail on the City’s notification procedures can be found in the City’s Emergency Response Plan (ERP), which also outlines communication protocol with local, regional, and State government agencies. The City’s ERP is discussed in more detail in Section 8.8.1.
The steps required to activate and implement the City’s WSCP are summarized as follows:
• STEP 1: The City identifies that water shortage conditions exist (due to supply shortfalls, State cutbacks, or emergency conditions).
• STEP 2: The City identifies the appropriate water shortage response measures to be considered in response to the water shortage level in the following three categories of demand management:
Voluntary Conservation Measures – The City authorizes implementation of voluntary demand reduction measures – implemented in Stages 1 and 2. Mandatory Conservation Measures – The City authorizes implementation of mandatory demand reduction measures, including enforcement actions and fines – implemented in Stages 3-6.
Allocation/Rate-Based Measures – The City authorizes implementation of water allocation and/or drought surcharge-based measures as deemed necessary to meet water shortage demand reduction targets while maintaining adequate water system revenues to operate the water system – implemented in Stages 3-6.
Actual demand management measures may be adjusted based on activation of any supply augmentation measures in parallel with demand reduction measures as well as the need to meet water system revenue requirements that are not being met due to the water shortage condition.
• STEP 3: City Council approves activation of the City’s WSCP and the suite of voluntary, mandatory, and/or allocation/rate-based measures to be implemented in response to a given water shortage level . The City must request approval of additional demand reduction measures as necessary to meet shortage level water use reduction targets. • STEP 4: City Council deactivates or downgrades the implemented WSCP measures as water shortage levels decrease or the need no longer exists.
The actions to be undertaken during each stage cannot be implemented until necessary City Council approvals have been executed. The types of measures that may be implemented in each stage are described below. These measures may be updated/altered based o n City Council direction and approval, State policy directives, emergency conditions, and/or to improve customer response. This six-stage response approach provides the City with the flexibility to address any given water shortage as it comes, and as conditions change.
Table 8-11 details the use restrictions for each stage of reduction declared by the City and outlines the penalties and charges associated with water use violations.
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Attachment 1
City of Sunnyvale
2020 Urban Water Management Plan
SECTION 8 – Water Shortage Contingency Planning
www.hydroscience.com
Table 8-11: Demand Reduction Actions
Shortage
Level Demand Reduction Actions
Reduction in
Shortage
Gap (%)
Penalty, Charge, or
Enforcement
Normal
Permanent water use prohibitions please refer to City’s Municipal Code 12.34.020 • Allowing plumbing fixtures to leak
• Using potable water in a manner where it floods premises and runoff into the street • Using a hose to wash vehicles without shut off valve
• Using a hose to wash driveways, sidewalks (except for health and safety) • Service of water to restaurants patrons without being requested • Installation of single pass cooling process in new construction • Sprinkler irrigation between the hours of 9 AM – 6 PM when daylight savings is in effect
• Irrigating for more than 15 minutes per day per station • Irrigation with potable water during and within 48 hours after measurable rainfall is prohibited
• Irrigation with potable water of ornamental turf on public street medians • Operators of hotels and motels shall provide guests with the option of choosing not to have towels and linens laundered daily
• Use of decorative fountains1 without recirculation
• Irrigating landscapes outside newly constructed homes or buildings in a manner inconsistent with regulations or other requirements established by the California Building Standards Commission and the Department of Housing and Community Development
≤ 10% No
Stage 1
up to 10%
• All the above
• Expand public information campaign which includes water use surveys and promoting available rebate programs such as turf replacement, water use efficiency devices, or conversion to recycled water if available
• Enforcement of permanent water use restriction Ordinance (Muni Code 12.34.020) • Decrease hydrant/line flushing (unless for public health or safety) 10% No
Stage 2
up to 20%
• All the above
• Increase water waste patrols and enforcement of permanent water use restriction Ordinance (Muni Code 12.34.020)
• Set maximum weekly three-day irrigation schedule
• Reduce system water loss
20%
• 1st and 2nd violation: $0 –
written warning
• 3rd violation: $250
• 4th violation: $500
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Attachment 1
City of Sunnyvale
2020 Urban Water Management Plan
SECTION 8 – Water Shortage Contingency Planning
www.hydroscience.com
Shortage
Level Demand Reduction Actions
Reduction in
Shortage
Gap (%)
Penalty, Charge, or
Enforcement
Stage 3
up to 30%
• All the above
• Irrigation of ornamental landscapes with potable water more than two days per week is prohibited
• Washing vehicles with potable water except at commercial vehicle washing facility • Implement or modify drought rate structure or surcharge • Increase frequency of meter reading
30%
• Fine for non-essential water
uses as described in City
ordinance: Not to exceed
$1,000
• Cost recovery for Installation
and removal of flow restricting
valves: $100
Stage 4
up to 40%
• All the above
• Water allocation may be imposed
• New installations of lawns
• Irrigating with potable water of golf courses except for tees and greens • Use of decorative fountains1
• New swimming pool or pond construction
• Filling or refilling swimming pools
40%
• Fine for non-essential water
uses and those listed in
demand reduction action: Not to
exceed $1,000
• Cost recovery for Installation
and removal of flow restricting
valves: $100
Stage 5
Up to 50%
• All the above
• Moratorium or net zero demand increase on new connections • New swimming pool or pond construction
• Filling or refilling swimming pools
• Outdoor watering December through March
• Watering turf, grass or dichondra lawns (can provide minimal water for sports playing fields)
50%
• Fine for non-essential water
uses and those listed in
demand reduction action: Not to
exceed $1,000
• Cost recovery for Installation
and removal of flow restricting
valves: $100
Stage 6
Greater
than 50%
• All the above
• Landscape irrigation with potable water of any City-owned premises or businesses where recycled water is available for connection
• Irrigation of ornamental landscapes with potable water • Watering turf, grass or dichondra lawns with potable water including sports and playing fields and tees and greens for golf courses
>50%
• Fine for non-essential water
uses and those listed in
demand reduction action: Not to
exceed $1,000
• Cost recovery for Installation
and removal of flow restricting
valves: $100
Note:
1. “Decorative fountains” are considered ornamental water features that are artificially supplied with water and include ponds, lakes, waterfalls, and fountains .
These facilities are considered ornamental and not for recreation.
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Attachment 1