SYS T
Public Draft
2025 Urban Water
Management Plan
April 2026
PREPARED BY:
80 Blue Ravine Road, Suite 280
Folsom, CA 95630
(916) 608-2212
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2025 URBAN WATER MANAGEMENT PLAN
PREPARED FOR
CITY OF STOCKTON
MUNICIPAL UTILITIES DEPARTMENT
APRIL 2026
PUBLIC DRAFT
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I
Table of Contents
Executive Summary ............................................................................................................... 1 Lay Description ...................................................................................................................... 2 1 Introduction .................................................................................................................... 1-1
1.1 Background .................................................................................................................... 1-1
1.2 System Overview ........................................................................................................... 1-1
1.3 Content of the UWMP ................................................................................................... 1-2
1.4 Lay Description .............................................................................................................. 1-3
1.5 Anticipated Document Use ........................................................................................... 1-3
1.6 UWMP Organization ..................................................................................................... 1-3 2 Plan Preparation .............................................................................................................. 2-1
2.1 Basis for Preparing a Plan .............................................................................................. 2-1
2.2 Individual or Regional Planning and Compliance .......................................................... 2-2
2.3 Regional Planning .......................................................................................................... 2-2
2.4 Fiscal or Calendar Year and Units of Measure .............................................................. 2-2
2.5 Coordination and Outreach .......................................................................................... 2-3
2.5.1 Wholesale and Retail Coordination ................................................................................... 2-3
2.5.2 Coordination with Other Agencies and the Community .................................................... 2-3
2.5.3 Notice to Cities and Counties ............................................................................................. 2-4 3 System Description .......................................................................................................... 3-1
3.1 General Description....................................................................................................... 3-1
3.2 Service Area and Boundary ........................................................................................... 3-3
3.3 Service Area Climate ..................................................................................................... 3-3
3.4 Service Area Population and Demographics ................................................................. 3-5
3.4.1 Population Projections ....................................................................................................... 3-7
3.4.2 Service Area Demographics and Socioeconomics ............................................................. 3-7
3.5 Land Uses Within the Service Area ............................................................................. 3-10
3.5.1 Existing Land Use ............................................................................................................. 3-10
3.5.2 Projected Land Use .......................................................................................................... 3-10 4 Water Use Characterization ........................................................................................... 4-15
4.1 Non-Potable vs. Potable Water Use ............................................................................ 4-15
4.2 Past, Current, and Projected Water Use by Sector ..................................................... 4-15 EXHIBIT 1
II
4.2.1 Past Water Use ................................................................................................................. 4-16
4.2.2 Current Water Use ........................................................................................................... 4-17
4.2.3 Projected Water Use ........................................................................................................ 4-18
4.2.4 Water Use for Lower Income Households ....................................................................... 4-19
4.3 Estimated Future Water Savings ................................................................................. 4-20
4.4 Distribution System Water Loss .................................................................................. 4-21
4.5 Data Provided to Wholesale Agency – To Be Developed in Future Submittal ............. 4-1
4.6 Climate Change ............................................................................................................. 4-1 5 SB X7-7 Baselines, 2020 Targets, and 2025 Reporting ....................................................... 5-1
5.1 Compliance with 20% by 2020 Water Use Target......................................................... 5-1 6 Water Service Reliability and Drought Risk Assessment .................................................... 6-1
6.1 Reliability Assessment Approach .................................................................................. 6-1
6.2 Service Area and Supply Overview ................................................................................ 6-1
6.3 Surface Water Supplies ................................................................................................. 6-4
6.3.1 San Joaquin River Diversion ............................................................................................... 6-4
6.3.2 Stockton East Water District .............................................................................................. 6-5
6.3.3 Woodbridge Irrigation District ........................................................................................... 6-5
6.4 Groundwater Supplies ................................................................................................... 6-6
6.4.1 Groundwater Sources ........................................................................................................ 6-6
6.4.2 Operational Role of Groundwater ..................................................................................... 6-8
6.4.3 Updated Groundwater System Condition and Capacity .................................................... 6-8
6.4.4 Groundwater Reliability and Planning Considerations .................................................... 6-10
6.5 Water Supply Data (Past Five Years) ........................................................................... 6-11
6.6 Other Water Supplies .................................................................................................. 6-12
6.6.1 Wastewater Collection ..................................................................................................... 6-12
6.6.2 Recycled Water ................................................................................................................ 6-15
6.7 Water Supply Reliability Projects ................................................................................ 6-16
6.7.1 Sodium Hypochlorite Facility ........................................................................................... 6-18
6.7.2 Land Annexation .............................................................................................................. 6-18
6.7.3 Advanced Metering Infrastructure (AMI) ........................................................................ 6-18
6.8 Summary of Water Supply Reliability ......................................................................... 6-18
6.9 Energy Intensity ........................................................................................................... 6-20 EXHIBIT 1
III
7 Water Supply Reliability and Drought Risk Assessment .................................................... 7-1
7.1 Purpose and Planning Framework ................................................................................ 7-1
7.2 Water Supply Reliability Assessment ............................................................................ 7-1
7.2.1 SEWD Supply Assessment .................................................................................................. 7-1
7.2.2 WID Supply Assessment ..................................................................................................... 7-2
7.2.3 San Joaquin River Supply Assessment ............................................................................... 7-3
7.2.4 City of Stockton (COS) Groundwater Wells........................................................................ 7-4
7.2.5 Normal Year Supply and Demand Comparison .................................................................. 7-5
7.2.6 Single Dry Year Supply and Demand Comparison.............................................................. 7-6
7.2.7 Multiple Dry Years Supply and Demand Comparison ........................................................ 7-7
7.3 Drought Risk Assessment (DRA) .................................................................................... 7-9
7.4 DRA Water Source Reliability ...................................................................................... 7-10
7.5 Summary ..................................................................................................................... 7-11 8 Water Shortage Contingency Plan .................................................................................... 8-1
8.1 City Water Shortage Contingency Plan ......................................................................... 8-1
8.2 Seismic Risk Assessment and Mitigation Plan ............................................................... 8-1
8.3 Water Shortage Contingency Plan Adoption, Submittal, and Availability .................... 8-2 9 Demand Management Measures ..................................................................................... 9-1
9.1 Water Conservation Program Overview ....................................................................... 9-1
9.2 Water Waste Prevention Ordinances ........................................................................... 9-1
9.2.1 DMM Description ............................................................................................................... 9-1
9.2.2 Implementation over the Past Five Years .......................................................................... 9-1
9.2.3 Plans for Continued Implementation / Planned Activities ................................................ 9-1
9.3 Metering ........................................................................................................................ 9-1
9.3.1 DMM Description ............................................................................................................... 9-1
9.3.2 Implementation over the Past Five Years .......................................................................... 9-2
9.3.3 Plans for Continued Implementation / Planned Activities ................................................ 9-2
9.4 Conservation Pricing ..................................................................................................... 9-2
9.4.1 DMM Description ............................................................................................................... 9-2
9.4.2 Implementation over the Past Five Years .......................................................................... 9-2
9.4.3 Plans for Continued Implementation / Planned Activities ................................................ 9-2
9.5 Public Education and Outreach ..................................................................................... 9-2 EXHIBIT 1
IV
9.5.1 DMM Description ............................................................................................................... 9-2
9.5.2 Implementation over the Past Five Years .......................................................................... 9-3
9.5.3 Plans for Continued Implementation/Planed Activities .................................................... 9-4
9.6 Programs to Assess and Manage Distribution System Real Loss .................................. 9-4
9.6.1 DMM Description ............................................................................................................... 9-4
9.6.2 Implementation over the Past Five Years .......................................................................... 9-4
9.6.3 Plans for Continued Implementation / Planned Activities ................................................ 9-4
9.7 Water Conservation Program Coordination and Staffing Support ............................... 9-5
9.7.1 DMM Description ............................................................................................................... 9-5
9.7.2 Implementation over the Past Five Years .......................................................................... 9-5
9.7.3 Plans for Continued Implementation / Planned Activities ................................................ 9-5 10 Plan Adoption, Submittal, and Implementation ............................................................ 10-1
10.1 Notice of Plan Preparation ...................................................................................... 10-1
10.1.1 Notices to Cities, Counties, and the Public ...................................................................... 10-1
10.2 Public Hearing and Adoption - To Be Developed in Future Submittal .................... 10-1
10.3 Plan Submittal - To Be Developed in Future Submittal ........................................... 10-2
10.3.1 Submitting a UWMP and Water Shortage Contingency Plan to DWR - To Be Developed in Future Submittal .............................................................................................................................. 10-2
10.3.2 Electronic Data Submittal - To Be Developed in Future Submittal .................................. 10-2
10.3.3 Submitting a UWMP, Including WSCP, to the California State Library - To Be Developed in Future Submittal .............................................................................................................................. 10-2
10.3.4 Submitting a UWMP to Cities and counties - To Be Developed in Future Submittal ...... 10-2
10.4 Public Availability - To Be Developed in Future Submittal ...................................... 10-2
10.5 Notification to Public Utilities Commission - To Be Developed in Future Submittal 10- 2 10.6 Plan Implementation - To Be Developed in Future Submittal ................................ 10-2
10.7 Amending an Adopted Urban Water Management Plan - To Be Developed in Future Submittal ................................................................................................................................ 10-2
10.7.1 Amending a UWMP or WSCP - To Be Developed in Future Submittal ............................ 10-2
10.7.2 Submitting Revised Water Shortage Contingency Plan - To Be Developed in Future Submittal 10-2
10.8 California Department of Water Resources Review of Submitted Plans - To Be Developed in Future Submittal .............................................................................................. 10-2 EXHIBIT 1
V
List of Figures
Figure 1-1: COSMUD Water Service Areas ........................................................................... 1-5 Figure 3-1: Service Area Facilities ........................................................................................ 3-2 Figure 3-2: Monthly Average Temperatures Within the City ................................................ 3-4 Figure 3-3: Monthly Average Rainfall and Evapotranspiration ............................................. 3-5 Figure 3-4: Screenshot of the City's Boundary Uploaded into the DWR Population Tool ....... 3-6 Figure 3-5: Major Languages Spoken at Home ..................................................................... 3-8 Figure 3-6: Population by Race ............................................................................................ 3-8 Figure 3-7: Bedroom Count in Occupied Housing Units ................. Error! Bookmark not defined.
Figure 3-8: Home Construction Year .................................................................................... 3-8 Figure 3-9: Exiting Land Use Designations ......................................................................... 3-13 Figure 3-10: New and Upcoming Developments ................................................................ 3-14 Figure 6-1: Existing Water Supply Sources ........................................................................... 6-3 Figure 6-2: Active Groundwater Wells in COSMUD Service Area .......................................... 6-7 Figure 6-3: Percent Water Supply by Source ...................................................................... 6-11 EXHIBIT 1
VI
List of Tables
Table 2-1: Public Water Systems (DWR Table 2-1 Retail) ..................................................... 2-1 Table 2-2: Plan Identification (DWR Table 2-2 Retail) .......................................................... 2-2 Table 2-3: Supplier Identification (DWR Table 2-3 Retail) .................................................... 2-3 Table 2-4: Water Supplier Information Exchange (DWR Table 2-4 Retail) ............................. 2-3 Table 3-1: Population - Current and Projected ..................................................................... 3-7 Table 3-2: Future Planned Development within COSMUD Water Service Area ................... 3-10 Table 4-1: Historical Use by Sector .................................................................................... 4-17 Table 4-2: 2025 Actual Total Uses for Potable and Non-Potable Water (DWR Table 4-1 Retail) ................................................................................................................................. 4-18 Table 4-3: Projected Water Use (DWR Submittal Table 4-2 Retail) ..................................... 4-19 Table 4-4: Inclusion in Water Use Projections (DWR Submittal Table 4-3 Retail) ................ 4-20 Table 4-5: Water Loss Audit Reporting (DWR Submittal Table 4-5 Retail) ........................... 4-22 Table 4-6: Progress Towards 2028 Water Loss Standard (Table 4-6 Retail) ........................... 4-1 Table 5-1: SB X7-7 2020 Target Progress (DWR Submittal Table 5-1 Retail) .......................... 5-2 Table 6-1: Summary of Well Facilities .................................................................................. 6-9 Table 6-2: Volume of Groundwater Pumped in Past Five Years (DWR Table 6-1 Retail)……..6-10 Table 6-3: Total Water Supply per Year (AFY)…………………………………………………………………...6-11 Table 6-4: Wastewater Collected Within Service Area in 2025 (DWR Table 6-2 Retail)………6-13 Table 6-5: Wastewater Treatment and Discharge Within Service Area in 2025 (DWR Table 6-3 Retail)……………………………………………………………………………………………………………………..….6-14 Table 6-6: Recycled Water Direct Beneficial Use Within Service Area (DWR Table 6-4 Retail) ………………………………………………………………………………………………………………………………………...6-16 Table 6-7: 2020 Recycled Water Use Projection and 2025 Actual Use (DWR Table 6-5 Retail) ………………………………………………………………………………………………………………………………………...6-16 Table 6-8: Methods to Encourage Future Recycled Water Use (DWR Table 6-6 Retail)…..….6-16 Table 6-9: Expected Future Water Supply Projects or Programs (DWR Table 6-7 Retail)….…6-17 Table 6-10: Water Supplies - 2025 Actual (DWR Table 6-8 Retail)………………………………….…. 6-19 Table 6-11: Water Supplies - Projected (DWR Table 6-9 Retail)………………………………..……… 6-19 Table 6-12: Energy Intensity (DWR Table 0-1B)……………………………………………………...……… 6-20 Table 7-1: Basis of Water Year Data for SEWD (DWR Table 7-1 Retail) ................................. 7-2 Table 7-2: Basis of Water Year Data for WID (DWR Table 7-1 Retail) .................................... 7-3 Table 7-3: Basis of Water Year Data for the San Joaquin River (DWR Table 7-1 Retail) ......... 7-4 Table 7-4: Basis of Water Year Data for COS Groundwater Wells (DWR Table 7-1 Retail) ..... 7-5 Table 7-5: Normal Year Supply and Use Comparison (DWR Table 7-2 Retail) ........................ 7-6 Table 7-6: Single Dry Year Supply and Use Comparison (DWR Table 7-3 Retail) .................... 7-7 Table 7-7: Multiple Dry Years Supply and Use Comparison (DWR Table 7-4 Retail) .............. 7-8 Table 7-8: Five-Year Drought Risk Assessment (DWR Table 7-5 Retail) ............................... 7-10 EXHIBIT 1
VII
List of Attachments
Attachment A: UWMP Checklist Arranged By Subject
Attachment B: DWR Standardized Uwmp Tables For Retail Urban Water Suppliers Attachment C: DWR Population Tool Input And Output
Attachment D: 2025 Water Shortage Contingency Plan
Attachment E: Water Supply Redundancy Evaluation
Attachment F: SEWD Contract
Attachment G: WID Contract
Attachment H: SMC Chapters 13.28 and 13.32
Attachment I: 2021 COS Water Master Plan Update 2021
Attachment J: City of Stockton 2020 Sphere of Influence Attachment K: 2040 General Plan - Envision Stockton
Attachment L: SAWS Water Education Program Annual Report Attachment M: Classroom Aquarium Education Program Slides Attachment N: Notification Letters to Cities and Counties EXHIBIT 1
1 EXECUTIVE SUMMARY
Executive Summary
The City of Stockton Municipal Utilities Department (COSMUD) prepared this 2025 Urban Water Management Plan (UWMP) to comply with the California Urban Water Management Planning Act.
The UWMP serves as the COSMUD’s long-term planning document for managing potable water supplies and demands over a 25-year planning horizon through 2050. This Plan updates the COSMUD’s 2020 UWMP and reflects current system conditions, updated planning assumptions, and applicable state requirements. For purposes of this UWMP, the terms “COSMUD” and “City” are used interchangeably to refer to the City of Stockton’s Municipal Utilities Department and its municipal water system. The term “City of Stockton” is used when referring to demographics and limits specific to the City of Stockton independent from COSMUD’s service area.
SERVICE AREA AND WATER SYSTEM
COSMUD provides potable water service to the North and South Stockton service areas, while the central portion of the City is served by a private water utility. As of the end of 2025, COSMUD served approximately 51,887 service connections within a service area population of about 191,000. The City operates a diversified, conjunctive-use water system designed to provide reliable service under a wide range of hydrologic and operational conditions.
WATER SUPPLY PORTFOLIO
The City’s water supply portfolio includes surface water diversions from the San Joaquin River under the City’s water rights, treated potable water purchased from the Stockton East Water District (SEWD), untreated surface water purchased from the Woodbridge Irrigation District (WID) and treated at the City’s Delta Water Treatment Plant, and groundwater extracted from municipal wells in the Eastern San Joaquin Groundwater Basin. These supplies are operated as an integrated system to balance reliability, sustainability, and operational flexibility. Surface water supplies are prioritized during normal conditions, while groundwater provides an essential supplemental and drought-response supply.
WATER USE AND DEMAND PROJECTIONS
The UWMP evaluates historical, current, and projected water use by customer sector and incorporates anticipated population growth, land use planning, and conservation requirements into demand projections. Projected demands are informed by the City’s adopted General Plan, Sphere of Influence planning documents, and the 2021 Water Master Plan Update. While overall demand is expected to increase over time, conservation programs and efficiency standards are incorporated into projections to help manage future water use.
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EXECUTIVE SUMMARY 2025 UWMP
2 WATER SUPPLY RELIABILITY AND DROUGHT RISK
Water supply reliability is assessed by comparing projected supplies and demands under normal-year, single dry-year, and multiple consecutive dry-year conditions. The analyses demonstrate that the City has sufficient water supplies to meet projected demands through 2050 under all evaluated conditions using its adopted conjunctive-use strategy. The UWMP also includes a Drought Risk Assessment that evaluates the potential impacts of future drought conditions on water supplies and informs long-term drought preparedness.
WATER SHORTAGE CONTINGENCY PLANNING
The UWMP incorporates the City’s Water Shortage Contingency Plan (WSCP), which establishes water shortage stages, response actions, enforcement authorities, and communication procedures.
The WSCP provides a structured framework for responding to water supply shortages caused by drought, regulatory constraints, infrastructure disruptions, or emergency events, while protecting public health and safety.
DEMAND MANAGEMENT AND WATER USE EFFICIENCY
COSMUD implements a comprehensive water conservation program that includes water waste prevention ordinances, universal metering, conservation-based rate structures, public education and outreach, and programs to assess and manage distribution system water loss. These demand management measures support efficient water use, reduce system losses, and contribute to long-term water supply reliability.
Lay Description
COSMUD’s 2025 UWMP documents the City’s water management planning efforts to ensure adequate water supply to meet demands over the next 25 years. The Plan evaluates current conditions and future needs over a 25-year planning period through 2050 and explains how the City will continue to provide water during normal conditions, droughts, and emergencies.
Based on the analyses in this UWMP, the City has sufficient water supplies to meet projected demands through 2050 under normal conditions as well as during single dry years and multiple consecutive dry years. Future water demands are based on expected population growth, land use planning, and historical water use patterns. Although demand is expected to increase over time, the City’s available supplies are adequate to meet these needs when operated as an integrated system.
As detailed in Chapter 4, the City’s projected demands in 2050 are 31,670 AFY which will be met by the City’s supply of 65,900 AFY. As discussed in Chapter 7, the City has adequate supply to meet demands during normal, single-dry, and multiple dry years. Through the Drought Risk Assessment (DRA), it was determined the City’s existing supplies will meet 2026-2030 demands in drought EXHIBIT 1
EXECUTIVE SUMMARY 2025 UWMP
3 conditions without the need to implement their Water Shortage Contingency Plan (WSCP) which is discussed in Chapter 8.
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CHAPTER 1 - INTRODUCTION
1 Introduction
This chapter provides a discussion of the fundamentals of the City of Stockton Municipal Utilities Department (COSMUD) 2025 Urban Water Management Plan (UWMP) including background information, a system overview, content of the UWMP, the required Lay Description of the UWMP, the anticipated document use, and the organization of this UWMP. COSMUD is the City of Stockton’s (City) department responsible for water, wastewater, and stormwater utilities. For purposes of this UWMP, the terms “COSMUD” and “City” are used interchangeably to refer to the City of Stockton’s Municipal Utilities Department and its municipal water system. The term “City of Stockton” is used when referring to demographics and limits specific to the City of Stockton independent from COSMUD’s service area.
1.1 Background
This UWMP has been prepared for the City in compliance with Division 6, Part 2.6, of the California Water Code (CWC), Sections 10610 through 10645. The 1983 bill mandated urban water suppliers to create a UWMP for long-term water supply planning, outlining how they will ensure sufficient water resources for current and future needs.
Urban water suppliers having more than 3,000 service connections or supplying more than 3,000 acre-feet per year for retail or wholesale are required to submit an UWMP every 5 years to the California Department of Water Resources (DWR). The UWMP deadline for the 2025 cycle is set for July 1, 2026. The 2025 UWMP serves as an update to the 2020 plan, originally submitted to DWR in June 2021, with subsequent data provided in March 2022.
DWR released the final 2025 UWMP Guidebook in February 2026 which has been updated from the 2020 version. COSMUD’s UWMP has been developed in close consultation with DWR’s 2025 Guidebook, utilizes the DWR’s guidance plan’s checkboxes, and follows the recommended organization and outline presented in the Guidebook. Alongside the 2025 UWMP, the COSMUD also updated the previously developed Water Storage Contingency Plan (WSCP), which is included in this report. The WSCP outlines the City's approach to managing both expected and unexpected water shortages.
1.2 System Overview
The City of Stockton is in the Central Valley of California, approximately 50 miles south of Sacramento. The San Joaquin River originates in the Sierra Nevada and flows westward across the San Joaquin Valley before turning north and ultimately joining the Sacramento River at the Sacramento–San Joaquin Delta. COSMUD provides water service to the northern and southern portions of the City of Stockton. The California Water Service Company (Cal Water) provides water EXHIBIT 1
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service to Stockton's central area. This UWMP does not include the central area of the City of Stockton within its scope.
The North Stockton water service area is mostly residential, bordered by Eight Mile Road to the north, Cascade and Columbia Railroad to the east, Calaveras River to the south, and the City of Stockton limits to the west. The South Stockton water service area includes residential neighborhoods on the west side, along with industrial and agricultural land. Its boundaries are generally French Camp Slough to the north, the City of Stockton limits to the east and south, and the San Joaquin River to the west. As of the end of 2025, COSMUD serves 51,887 connections. Figure 1-1 illustrates COSMUD’s service area.
COSMUD operates a diversified, conjunctive use potable water system serving the North and South Stockton service areas. The system relies on a combination of locally controlled surface water, purchased surface water, and groundwater supplies to provide operational flexibility and long-term reliability. Surface water sources include direct diversions from the San Joaquin River under the City’s water rights, treated potable water purchased from the Stockton East Water District (SEWD), and untreated surface water purchased from the Woodbridge Irrigation District (WID) and treated at the City’s Delta Water Treatment Plant.
SEWD supplies originate from regional reservoirs on the Stanislaus and Calaveras Rivers and provide treated water delivered directly into the City’s distribution system. WID supplies originate from the Mokelumne River and support the City’s surface water portfolio, with additional supply becoming available as agricultural lands are annexed and converted to urban use. Groundwater extracted from municipal wells in the Eastern San Joaquin Groundwater Basin supplements surface water supplies and serves as a critical reliability and drought response resource. COSMUD operates these sources as an integrated system, prioritizing surface water during normal conditions to support groundwater sustainability while maintaining groundwater capacity to respond to dry years, infrastructure outages, and emergency conditions.
Additional details on the City’s water system, including water rights and other supply reliability information, are provided in Chapter 6.
1.3 Content of the UWMP
The UWMP serves as a planning tool to help the City manage and deliver water to its service area, outlining actions to address changing water and management conditions. The City’s 2025 UWMP is a comprehensive guide for planning for a safe and adequate water supply. This UWMP provides a reliable water management action plan that can be used as a reference as conditions change and management decisions arise.
This UWMP addresses all subjects required by the Urban Water Management Planning Act (“Act”) which permits “levels of water management planning commensurate with the numbers of EXHIBIT 1
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customers served and the volume of water supplied.” All applicable sections of the Act are discussed in this UWMP, and a completed copy of the 2025 Urban Water Management Plan Checklist organized by subject is included in Attachment A.
1.4 Lay Description
CWC §10630.5 requires each UWMP to include a Lay Description that explains the agency’s water system and planning approach in clear, nontechnical language. The Lay Description must describe, at a high level, how much water the agency has available on a reliable basis, how much water it expects to need in the foreseeable future, and the strategies the agency will use to meet those needs. It must also summarize the key challenges facing the agency and include any additional information necessary to provide a general understanding of the agency’s overall water management plan.
Consistent with the DWR Urban Water Management Plan Guidebook, a lay description and summary of COSMUD’s water system, supplies, and demands is provided in the Executive Summary.
1.5 Anticipated Document Use
The City is committed to implementation of the projects, plans, and discussions provided within this document. The 2025 UWMP is intended to serve as a general, flexible, and open-ended document that periodically can be updated to reflect changes in water supply trends, and conservation and water use efficiency policies. This UWMP, along with other City planning documents, will be used by City staff to guide water use and management efforts through the year 2030, when the next UWMP is required.
1.6 UWMP Organization
The City's UWMP was prepared in accordance with DWR’s 2025 Guidebook. This plan adheres to the recommended structure, which reflects revisions from earlier guidebooks. All tables recommended in the DWR Guidebook have been inserted into the appropriate UWMP chapters, and are included as in Attachment B.
This 2025 UWMP is organized into the following chapters:
• Chapter 1: Introduction
• Chapter 2: Plan Preparation
• Chapter 3: Service Area Description
• Chapter 4: Water Use Characterization
• Chapter 5: SBX7-7 Baselines, 2020 Targets and 2025 Reporting • Chapter 6: Normal-Year Water Supply Characterization
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• Chapter 7: Water Service Reliability and Drought Risk Assessment • Chapter 8: Water Shortage Contingency Plan
• Chapter 9: Demand Management Measures
• Chapter 10: Plan Adoption, Submittal and Implementation This 2025 UWMP also contains the following appendices of supplemental information and data:
• Attachment A: UWMP Checklist Arranged by Subject
• Attachment B: DWR Standardized UWMP Tables for Retail Urban Water Suppliers • Attachment C: DWR Population Tool Input and Output
• Attachment D: Draft 2025 Water Shortage Contingency Plan • Attachment E: Water Supply Redundancy Evaluation
• Attachment F: SWED Contract
• Attachment G: WID Contract
• Attachment H: SMC Chapters 13.28 and 13.32
• Attachment I: 2021 COS Water Master Plan Update 2021
• Attachment J: City of Stockton 2020 Sphere of Influence • Attachment K: 2040 General Plan - Envision Stockton
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CHAPTER 2 – PLAN PREPARATION
2 Plan Preparation
This chapter covers the methods involved in creating the 2025 UWMP. It discusses the rationale behind the plan, regional planning considerations, whether fiscal or calendar years are used for reporting, units of measurement, as well as how the plan is coordinated and how outreach is conducted.
The City prepared this UWMP with the assistance of its consultant, Verdantas, Inc, as permitted by Section 10620(e) of the CWC. During the preparation of the UWMP, previously developed planning documents for the City, including but not limited to the 2020 UWMP and the 2021 City of Stockton Water Master Plan Update, were reviewed and information from those documents incorporated, as applicable, into this UWMP.
2.1 Basis for Preparing a Plan
In accordance with the Urban Water Management Planning Act, urban water suppliers are required to prepare an UWMP every 5 years. An urban water supplier is defined as a supplier, either publicly or privately owned, providing water for municipal purposes either directly or indirectly to more than 3,000 customers or supplying more than 3,000 acre-feet (AF) of water annually. Every person that becomes a supplier is required to adopt an UWMP within one year of becoming a supplier. As demonstrated in Table 2-1, the City is a retail urban water supplier that provides water supplies to 51,887 potable water customers (connections) and supplies 32,060 AF of potable water.
Table 2-1: Public Water Systems (DWR Table 2-1 Retail)
Submittal Table 2-1 Retail: Public Water Systems
Public Water System
Number
Public Water System
Name
Number of Municipal
Connections 2025
Volume of
Water Supplied
2025
(AF)
CA3910012 City of Stockton 51,887 32,060
Total 51,887 32,060
NOTES: Volume of water supplied is in acre-feet (AF)
COSMUD is categorized as a Public Water System (PWS) according to the California Health and Safety Code 116275. A PWS is defined as:
“…a system for the provision of water for human consumption through pipes or other constructed conveyances that has 15 or more service connections or regularly serves at least 25 individuals daily at least 60 days out of the year”.
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2.2 Individual or Regional Planning and Compliance
As shown in Table 2-2, the City has prepared the 2025 UWMP on an individual reporting basis, covering only the COSMUD service area as previously shown in Figure 1-1. The City has coordinated its efforts with SEWD, WID, Cal Water, San Joaquin County, and the Eastern San Joaquin Groundwater Authority.
Table 2-2: Plan Identification (DWR Table 2-2 Retail)
2.3 Regional Planning
The City has prepared this 2025 UWMP on an individual reporting basis; however, the City regularly collaborates with SEWD, WID, Cal Water, Eastern San Joaquin Groundwater Authority and San Joaquin County. These agencies work together to address water supply issues and assess both the region’s available water resources and projected demands for the SEWD 2025 UWMP. SEWD additionally supported the City during the preparation of this plan. Detailed information regarding the anticipated future availability and reliability of water supplies from SEWD is provided in Chapters 6 and 7 of this UWMP.
2.4 Fiscal or Calendar Year and Units of Measure
The City’s water supply and demand data are all presented on a calendar year basis and in units of acre-feet (AF). These units are used consistently for all data presented within this UWMP.
COSMUD is a water retailer, and therefore, has presented all data into the DWR standard tables that are prescribed for retailers. Table 2-3 summarizes the reporting conventions used in this UWMP.
Select
Only
One
Type of Plan Name of RUWMP or Regional Alliance
Individual UWMP
Water Supplier is also a
member of a RUWMP n/a
Water Supplier is also a
member of a Regional
Alliance
n/a
Regional Urban Water Management
Plan (RUWMP) n/a
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Table 2-3: Supplier Identification (DWR Table 2-3 Retail) Type of Supplier (select one or both)
Supplier is a wholesaler
Supplier is a retailer
Fiscal or Calendar Year (select one)
UWMP Tables are in calendar years
UWMP Tables are in fiscal years
If using fiscal years provide month and date that the fiscal year begins (mm/dd)
Unit AF
2.5 Coordination and Outreach
This section provides a discussion of the City’s coordination efforts with surrounding water suppliers and with the public.
2.5.1 Wholesale and Retail Coordination
As shown in Table 2-4, the City purchases wholesale raw water from WID and treated water from SEWD. When a water agency depends on a wholesale provider for its water supply, both agencies must share details about their expected water supply and demand.
Table 2-4: Water Supplier Information Exchange (DWR Table 2-4 Retail) The retail Supplier has informed the following wholesale supplier(s) of projected water use in accordance with Water Code Section 10631 (h).
Wholesale Water Supplier Name
Stockton East Water District
Woodbridge Irrigation District
2.5.2 Coordination with Other Agencies and the Community The development of the 2025 UWMP has been coordinated with other agencies and the community.
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2.5.2.1 Coordination with Other Agencies
CWC §10620(d)(3) requires urban water suppliers to coordinate their Urban Water Management Plan (UWMP) preparation with relevant agencies in the region, including other water suppliers sharing a common source, water management agencies, and related entities.
The City sent 60-day notices to SEWD, WID, and Cal Water to inform them about the UWMP's development. Additionally, SEWD and WID provided data needed for the City to complete chapters 6 and 7 of this UWMP.
2.5.2.2 Coordination with the Community - To Be Developed in Future Submittal
2.5.3 Notice to Cities and Counties
CWC §10621(b) requires that agencies notify cities and counties to which they serve water that their UWMP is being updated and reviewed. The CWC specifies that this must be done at least 60-days prior to the public hearing. The City sent notices regarding their UWMP development to San Joaquin County, and San Joaquin County Groundwater Authority. Further discussion of notices to cities, counties, and the public is included in Chapter 10.0 of this UWMP.
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CHAPTER 3 – SYSTEM DESCRIPTION
3 System Description
This Chapter provides a description of the COSMUD’s water system, including a general description, service area boundary maps, climate, population, demographics, and land uses.
3.1 General Description
The City of Stockton is in San Joaquin County (County) within California’s northern San Joaquin Valley, adjacent to the San Joaquin River and the Sacramento–San Joaquin Delta and serves as the primary urban center within the County. Founded in 1849 during the California Gold Rush and incorporated in 1850, the City of Stockton developed as a river-based transportation and commercial hub and has since evolved into a diverse urban community within a predominantly agricultural region. Land uses within the service area include residential, commercial, industrial, and public facilities, while surrounding agricultural lands and associated processing, transportation, and port activities continue to influence regional water demands.
COSMUD is a public municipal water supplier operated by the City of Stockton. COSMUD was established to provide and manage potable water, wastewater, and stormwater services within the City in support of public health, regulatory compliance, and planned urban growth. COSMUD serves the North Stockton and South Stockton service areas, while the central portion of the City is served by a private water utility, Cal Water. As a City of Stockton department rather than an independent special district, COSMUD operates under the City of Stockton’s council–manager form of government, with policy oversight provided by the Stockton City Council and administrative responsibility delegated to the City Manager and Municipal Utilities Director.
COSMUD sources water by diverting supply from the San Joaquin River and buying raw water from WID, which is then processed at COSMUD's Delta Water Treatment Plant. Additionally, COSMUD purchases treated water from SEWD and extracts water from groundwater wells located in North Stockton and South Stockton. COSMUD’s current water system is composed of 12 active groundwater wells, three storage reservoir sites (7 reservoirs), and 584 miles of distribution and transmission pipe. A map of the COSMUD’s existing facilities is shown in Figure 3-1.
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3.2 Service Area and Boundary
The City of Stockton is in San Joaquin County in north-central California, within the northern San Joaquin Valley. The City of Stockton lies approximately 50 miles south of Sacramento and 70 miles east of San Francisco. Interstate 5 and California State Highway 99 run north-to-south along the western and eastern sides of the City of Stockton. California State Highway 4 runs east-to-west and connects Interstate 5 and California State Highway 99.
As of the end of 2025, COSMUD serves 51,887 connections within their service area. The service area is approximately 44 square miles and is made up of the North Stockton and South Stockton areas. Central Stockton is served by Cal Water. The North Stockton water service area is mostly residential, bordered by Eight Mile Road to the north, Cascade and Columbia Railroad to the east, Calaveras River to the south, and the City limits to the west. The South Stockton water service area includes residential neighborhoods on the west side, along with industrial and agricultural land. Its boundaries are generally French Camp Slough to the north, the City limits to the east and south, and the San Joaquin River to the west.
Of the 51,887 current connections:
• 49,315 (95.04%) of the connections are residential
• 1,578 (3.04%) of the connections are commercial and institutional • 975 (1.88%) of the connections are irrigation
• 19 (0.04%) of the connections are industrial
3.3 Service Area Climate
The City of Stockton’s climate characteristics include hot, dry summers and mild, and wet winters.
The Western Regional Climate Center (WRCC) maintains historic climate data for selected cities throughout the West. The Stockton Airport (AP) climate station is in South Stockton near the Stockton Metropolitan Airport. This station was selected to provide representative climate data for the City’s service area. Seventy-seven (77) years of historic data obtained from the WRCC web site (www.wrcc.dri.edu) for the Stockton AP station was utilized for this climate data analysis.
The lowest average monthly temperature occurs in the winter and is approximately 38 degrees Fahrenheit. The highest average monthly temperature reaches approximately 92 degrees Fahrenheit in the summer. Figure 3-2 presents the monthly average temperature based on historical data.
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Figure 3-2: Monthly Average Temperatures Within the City (Data Source: WRCC, Stockton AP Station)
The rainy season typically runs from November through March, with the heaviest rainfall observed between December and February. Summers are typically dry with little to no rainfall. Monthly precipitation during the winter months ranges from 1 to 2.5-inches. Low humidity conditions in the City of Stockton generally occur during the summer months from June through September. The moderately hot and dry weather during the summer months typically results in higher water demands.
The California Irrigation Management Information System (CIMIS) web site (www.cimis.water.ca.gov) tracks and maintains records of evapotranspiration (ETo) for select cities.
ETo statistics used for this system come from the Holt station, located approximately 12 miles east of the City. ETo is a standard way to estimate how much water plants need. It represents the amount of water that would evaporate and be used by a healthy, well-watered grass field and is measured in inches over time.
The monthly average ETo and monthly average precipitation are presented in inches in Figure 3-3.
As the figure indicates, a greater quantity of water is evaporated during June, July, and August in correlation to high temperatures and low humidity, which typically results in higher water demands. 30 40
50 60
70 80
90 100
TEMPERATURE [°F]
Max
Min
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Figure 3-3: Monthly Average Rainfall and Evapotranspiration (Data Source: CIMIS Holt Station 248, 2016-2025)
The City recognizes that climate change is expected to increase hydrologic variability within the service area, including hotter temperatures, longer and more frequent droughts, and more extreme precipitation events. These conditions may increase seasonal and peak water demands, reduce surface water reliability, and place additional stress on water system operations.
To account for these uncertainties, the UWMP evaluates water supply reliability under normal-year, single dry-year, and multiple consecutive dry-year conditions, which collectively reflect a range of potential future climate stresses. While climate change may increase the frequency and severity of drought conditions, the City’s diversified, conjunctive-use water supply portfolio and demand management programs provide flexibility to maintain reliable service. The Water Shortage Contingency Plan (WSCP) serves as the primary mechanism for managing short-term or extreme climate-driven supply disruptions. The WSCP is discussed in Chapter 8 and is included in Attachment D of this UWMP.
3.4 Service Area Population and Demographics
The DWR Population Tool, found on DWR’s 2025 UWMP website, was used to estimate both the current (2025) population and the population during the City’s baseline period. COSMUD’s water service area differs from the City boundaries, so the population tool shows only the population within the service area.
0 1
2 3
4 5
6 7
8 9
Inches
Average Rainfall
Average ETo
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The DWR Population Tool determines service area population for census years by extracting U.S.
Census data, at the block level, for City service boundaries that existed at each Census year in the tool (1990, 2000, and 2010). For census blocks that straddle the service area boundary, the tool determines the percentage of the census block’s land area that is within the service area boundary and applies that percentage to the census block population. Census data for 2025 is not yet available using this tool; therefore, the tool calculates the 2025 population using historical data and current number of service connections. The City’s service area used to determine the 2025 service area population is shown in Figure 3-4.
Figure 3-4: Screenshot of the City's Boundary Uploaded into the DWR Population Tool The 2025 population within the COSMUD service area was estimated to be 191,3021 based on the DWR Population tool. A summary of the input and output data from this tool is provided in Attachment C.
1 This population estimate is based on SDWIS population estimates. The population estimate will be updated when DWR Population tool becomes available.
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3.4.1 Population Projections
The City’s January 2021 Water Master Plan Update (2021 WMP)2, developed by West Yost Associates, outlines the projected future land uses that were determined by the City’s 2040 General Plan Update (2040 GPU)3 and April 2020 Sphere of Influence Plan/Municipal Service Review (April 2020 SOI/MSR Report)4
. The 2021 WMP determined the future planned development within the City’s water service area in the near-term (2030) and the future (2040). Future land use designations within the City's water service area include Single and Multi-Family Residential, Commercial, Industrial (limited to South Stockton), and Parks. The predominant focus of upcoming development plans is on single and multi-family residential units.
The 2021 WMP determined an annualized growth rate within the City of 1.44 percent. This estimate is based on the San Joaquin Council of Governments (SJCOG) population projections between 2020 and 2040 for the City. This annual growth rate was used to estimate the City’s projected population in 5-year increments from 2025 to 2050. The current and projected population within the City’s water service area is outlined in Table 3-1.
Table 3-1: Population - Current and Projected
Population
Served
2025 2030 2035 2040 2045 2050 (opt)
191,302* 205,478 220,705 237,060 254,627 273,496
NOTES: The 2025 population was estimated using the DWR Population Tool. The growth rate of 1.44% per year was used to estimate COSMUD’s Service Area population for the years 2030 through 2050.
*This population estimate is based on SDWIS population estimates. Will be updated when DWR Population tools become available.
3.4.2 Service Area Demographics and Socioeconomics
As previously stated, the COSMUD’s water service area spans the north and south portions of the City of Stockton; therefore, the United States Census Bureau’s City of Stockton profile was chosen as demographically representative for COSMUD’s service area. Figures 3-5 through 3-8 demonstrate the primary race, language, and household demographics based on the US Census Bureau’s 2020- 2024 ACS 5-year estimates5
and the US Bureau of Labor Statistics Economy at Glance6. 2 City of Stockton, 2021. Water Master Plan Update. City of Stockton, California. – Included in Attachment I 3 City of Stockton. 2018. Envision Stockton 2040 General Plan Update. City of Stockton, California. – Included in Attachment K
4 City of Stockton. 2020. Sphere of Influence Plan and Municipal Service Review. City of Stockton, California. – Included in Attachment J
5 https://www.census.gov/quickfacts/fact/table/stocktoncitycalifornia/IPE120224#IPE120224 6 https://www.bls.gov/eag/eag.ca_stockton_msa.htm#eag_ca_stockton_msa.f.1 EXHIBIT 1
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Figure 3-5: Major Languages Spoken at Home Figure 3-6: Population by Race
Figure 3-7: Bedroom Count in Occupied Figure 3-8: Home Construction Year Housing Units
English
51%
Spanish
31%
Asian and
Pacific
Islander
Languages
14%
Other IndoEuropean
Languages
4%
Hispanic or
Latino
45.35%
white
15.72%
Black or
African
American
10.61%
American
Indian and
Alaska Native
0.20%
Asian
22.62%
Native
Hawaiian and
Other Pacific
Islander
0.50%
Some Other
Race Alone
0.50%
Two or More
Races
4.50%
No
Bedrooms
6% 1
Bedroom
9%
2 or 3
Bedrooms
58%
4 or more
Bedrooms
27%
Before
1940
8.51%
1940-1979
45.56%
1980-2019
45.56%
2020 or
Later
0.38%
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The City of Stockton is predominantly Hispanic or Latino while the primary language spoken at home is English follow by Spanish. The following describes additional demographics and information about the City of Stockton:
• Population and Demographics
o The median age for the City of Stockton is 34.2 years. • Housing, Families and Living Arrangements:
o The average household size is 3.2 persons per household. o The median gross rent in the City of Stockton is $1,635. o The home ownership rate in the City of Stockton is 53.7%. o Figure 3-7 shows the bedroom count in occupied housing units o The median home construction year in the City of Stockton 1979. • Economy, Income, Education, and Poverty:
o The median household income for City of Stockton residents is $79,907. o 15.5% of all individuals and 22.5% of individuals under 18 are living in poverty. o The City of Stockton has an unemployment rate of 6.4% o The percentage of individuals aged 25 and up with at least a high school diploma is
77.5%. The percentage of individuals aged 25 and up with at least a bachelor’s degree is 20.0%.
• Health
o 10.1% of individuals under the age of 65 have a disability. o 7.7% of individuals under the age of 65 are without health insurance.
The City of Stockton’s demographic and housing characteristics have several implications for water management and planning. The City of Stockton’s relatively young population and larger average household size of 3.2 persons per household, combined with a substantial share of large single‑family homes, suggest higher residential indoor water demand and potential outdoor irrigation needs.
The predominance of older housing —over half of units constructed prior to 1980—indicates a continued need for infrastructure rehabilitation, leak reduction, and targeted water‑use efficiency programs to address aging plumbing and distribution systems.
Socioeconomic conditions, including moderate median household income, elevated poverty rates, and a diverse linguistic population, highlight the importance of affordability considerations, EXHIBIT 1
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equitable rate structures, customer assistance programs, and multilingual outreach for conservation and drought response.
3.5 Land Uses Within the Service Area
The City’s 2021 WMP land use projections are based on projected land uses from the 2040 General Plan Update and the April 2020 SOI/MSR Report. It identifies planned development in the City’s water service area through 2030 and 2040, including single- and multi-family residential, commercial, industrial (in South Stockton only), and parks. This section describes, in further detail, the existing and projected land use for COSMUD service area.
3.5.1 Existing Land Use
COSMUD’s North Stockton water service area consists primarily of residential, single and multifamily land uses, with some commercial and parks land designations. The South Stockton water service area includes residential neighborhoods on the west side but is primarily composed of land designated as industrial. Figure 3-9 shows a map of the City’s existing land use designations.
3.5.2 Projected Land Use
As previously stated, the City’s 2021 WMP projects future land use within the COSMUD service area by using projections acquired from the City’s 2040 GPU and the April 2020 SOI/MSR Report. The 2040 GPU defines anticipated development across sixteen study areas across the City, while the SOI/MSR Report addresses near-term (2030) development and associated municipal service needs.
Together, these documents provide for approximately 40,900 new residential dwelling units citywide, with SOI/MSR projects assumed to be completed by 2030 and remaining planned projects by 2040.
As listed in the City’s 2021 WMP, Table 3-2 provides an overview of anticipated development within the COSMUD water service area, categorized by land use designation in accordance with the 2040 GPU and SOI/MSR Report.
Table 3-2: Future Planned Development within COSMUD Water Service Area (Data Source: 2021 WMP)
Future Land Use
Designation
Units
Near-Term (2030)
Total Development
Future (2040) Total
Development
North Stockton
Single Family Residential DU 2,100 16,700
Multi Family Residential DU 500 4,212
Commercial Acres 23 167
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Future Land Use
Designation
Units
Near-Term (2030)
Total Development
Future (2040) Total
Development
Industrial Acres 0 0
Parks Acres 41 451
South Stockton
Single Family Residential DU 0 8,955
Multi Family Residential DU 0 1,575
Commercial Acres 55 273
Industrial Acres 1,354 1,753
Parks Acres 9 224
As of April 2025, the City’s planning website lists seven development agreements within COSMUD’s service area. Figure 3-10 shows the location of the major development projects listed in this section:
• Westlake at Spanos Park West (North Stockton): The development agreement facilitates construction of approximately 689.6 acres into a 2,800-unit residential community. This project is currently under construction.
• Crystal Bay (North Stockton): Planned residential community encompassing approximately 173 acres and 1,343 dwelling units, featuring a range of park and open space amenities in the northwest area of the City. This project has been approved but construction is pending. • Delta Cove (North Stockton): The addition of 1,545 residential units. This project has been approved but construction is pending.
• Cannery Park (North Stockton): This project initially proposed the construction of 1,116 single-family detached housing units and 210 multi-family housing units, 1,452,508 square feet of light industrial business parkland, and 1,078,763 square feet of commercial land use.
This project is under construction.
• Sanctuary (North Stockton): This project proposed 5,758 units of residential development on approximately 1,967 acres. This project is approved and pending construction. • Mariposa Industrial (South Stockton): This project will establish a new industrial development of seven warehouses on approximately 203.48 acres on six largely vacant parcels with agricultural uses and two residences. This project is under construction. • Mariposa Lakes (South Stockton): This project includes the addition of 10,566 residential units. The Mariposa Lakes site is comprised of approximately 3,810 acres of unincorporated EXHIBIT 1
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lands located four miles southeast of downtown Stockton and 3.5 miles northeast of the Stockton Metropolitan Airport. This project is approved and pending construction.
In an April 2024 Major Residential Project Map posted on the City’s planning webpage, the City lists six additional large residential projects within COSMUD’s service area in addition to the already listed City development agreements, including the 1,409-unit LeBaron Ranch Subdivision. These developments add up to approximately 5,350 additional residential units. Additionally, an Active Multi-Family Housing Development Map posted on the City’s planning webpage and updated in July 2024, lists five additional multi-family housing developments totaling approximately 870 units within the COSMUD service area.
North Stockton will experience the largest increase in residential development. The largest planned development within this area is the Sanctuary development. The Mariposa Lakes Project in South Stockton is the largest planned development within the City. Even though this development site falls within both the COSMUD and Cal Water service areas, the Water Master Plan Update conservatively assumes that COSMUD will provide water to the entire Mariposa Road Community area. The Mariposa Industrial development will also provide South Stockton with an increase in commercial and industrial development.
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CHAPTER 4 – WATER USE CHARACTERIZATION
4 Water Use Characterization
The purpose of this chapter is to summarize COSMUD’s use of potable water within their service area. To provide a complete picture of how the water is being allocated and used, the water use is divided by customer types. Once customer types are established, historical water use, current water use, and projected water use will be examined. COSMUD’s water loss data and future estimated savings are examined, alongside low-income household water use.
4.1 Non-Potable vs. Potable Water Use
Potable water is water which has been deemed safe for consumption and is treated to ensure there are no biological, chemical, or physical impurities within the final product. COSMUD solely supplies potable water within its service area and does not distribute non-potable water of any kind.
COSMUD gets its water from multiple sources, including surface water from the intake on the Sacramento San Joaquin Delta and Mokelumne River via wholesale water from Woodbridge Irrigation District (WID) which is then treated at the Delta Water Treatment Plant (DWTP). The disinfection process of DWTP uses chloraminate which is not compatible with free chlorine disinfection. The South Stockton service area uses free chlorine disinfection; therefore, the DWTP only serves the North Stockton service area.
Surface water imported from the Stanislaus River and Calaveras River is purchased from the wholesale source Stockton East Water District (SEWD). The surface water is treated by SEWD and can be distributed to the entire COSMUD service area.
There are twelve (12) active wells and four (4) standby wells in the North Stockton distribution area.
In the South Stockton distribution area, there are two (2) active and two (2) standby wells. The majority of COSMUD’s distribution network is made up of treated surface water, and the wells are used as supplementary water supplies when necessary.
4.2 Past, Current, and Projected Water Use by Sector
DWR identifies ten distinct categories of water use. Within COSMUD's service area, water use is tracked and reported in seven of these categories, while the remaining three are not applicable. The sectors that make up COSMUD’s service area include single family, multi-family, commercial, landscape, sales/transfers/exchanges to other suppliers, industrial, and other. The sectors in which COSMUD has identified their water use are defined below. • Single Family Residential – A single family dwelling unit. A lot with a free-standing building containing one dwelling unit that may include a detached secondary dwelling.
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• Multi-Family Residential – Multiple dwelling units contained within one building or several buildings within one complex.
• Commercial – A water user that provides or distributes a product or service. • Landscape – Water connections supplying water solely for landscape irrigation. Such landscapes may be associated with multi-family, commercial, industrial, or institutional/governmental sites, but are considered a separate water use sector if the connection is solely for landscape irrigation.
• Sales/Transfers/Exchanges to other Suppliers – DWR has included “Transfers” as a part of the Sales/Transfers/Exchanges to other Suppliers sector. COSMUD receives water from other suppliers and therefore would have a sector for “Transfers outlined in the UWMP water use sectors table. A transfer is considered a temporary or long-term change in the point of diversion, place of use, or purpose of use due to a transfer, sale, lease, or exchange of water.
• Industrial - A water user that is primarily a manufacturer or processor of materials as defined by the North American Industry Classification System (NAICS) code sectors 31 to 33, inclusive, or an entity that is a water user primarily engaged in research and development.
• Other – Any other water demand that is not adequately described by the water sectors defined above. System water losses are not to be reported in the “Other” category.
Furthermore, DWR has defined additional sectors which are not applicable in COSMUD’s water use case. The sectors not included within COSMUD’s service area include Conjunctive Use, Groundwater Recharge, Saline Intrusion Barriers, Agricultural, and Institutional/Governmental water use types.
4.2.1 Past Water Use
Table 4-1 outlines the historical water use by sector, as outlined in the UWMP from 2010, 2015, and 2020.
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Table 4-1: Historical Use by Sector
Use Type (Sector) 2010* 2015* 2020**
Single Family 18,639 13,764 15,758
Multi-Family 3,047 2,854 3,030
Commercial 4,471 3,652 4,700
Landscape 3,392 2,152 3,255
Sales/Transfers/Exchanges to other Suppliers 163 1,476 1,830 Industrial 642 723 709
Other (optional) 53 - 132
Distribution System Water Loss 3,107 1,699 4,991
Total 33,496 26,320 34,404
* Source: COSMUD 2020 UWMP Table 4-1
** Source: COSMUD 2020 UWMP Table 4-2
Note: Units are in acre-feet (AF)
Over a 10-year period, COSMUD’s water consumption has increased by less than 1,000 AF. This increase can be attributed to increased commercial consumption, sales/transfers/exchanges to other suppliers, and increased losses in the water distribution system. The data show a decrease in single family and multi-family use type within COSMUD’s service area.
4.2.2 Current Water Use
The current water use for COSMUD is reflected in Table 4-2. The sectors listed in the table reflect the sole water use sectors found within COSMUD’s service area.
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Table 4-2: 2025 Actual Total Uses for Potable and Non-Potable Water (DWR Table 4-1 Retail) Submittal Table 4-1 Retail: 2025 Actual Total Uses for Potable and Non-Potable Water Water Code Section 10631(d)(1)
Use Type
Additional Description
(as needed)
2025 Actual Water Use
Drop down list
May select each use multiple times
These are the only use types that
will be recognized by the WUEdata
online submittal tool
Level of
Treatment
When Delivered
(OPTIONAL)
Drop down list
Volume
(AF)
Add additional rows as needed
Single Family Potable 15,374
Multi-Family Potable 2,927
Commercial
Includes
Institutional/Governmental
use type
Potable 6,083
Landscape Irrigation Potable 3,400
Sales/Transfers/Exchanges to
other Suppliers
Metered to San Joaquin
County Potable 931
Industrial Potable 526
Other (optional) Hydrant Meters/Jumpers Potable 70
Distribution System Water
Loss Potable 2,749
Subtotal Potable 32,060
Subtotal Non-Potable 0
Total 32,060
NOTES: Volume is measured in Acre-Feet (AF)
4.2.3 Projected Water Use
Table 4-3 outlines the projected water use per sector from 2030 through 2050. Projected water demands were calculated assuming an annual population growth rate of 1.44%, or 7.20% every 5 years. This growth rate was applied as a generalized growth rate to each sector to make a conservative estimate of water demands in the next 25 years.
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Table 4-3: Projected Water Use (DWR Submittal Table 4-2 Retail) Submittal Table 4-2 Retail: Total Uses of Potable, and Non-PotableWater - Projected Water Code Section 10631(d)(1)
Use Type
Additional
Description
(as needed)
Projected Water Use
(Report To the Extent that Records are Available)
Drop down list
May select each use multiple
times
These are the only Use Types
that will be recognized by the
WUEdata online submittal tool
Level of
Treatment
When
Delivered
(OPTIONAL)
Drop down list
2030 2035 2040 2045 2050
(AF) (AF) (AF) (AF) (AF)
Single Family Potable 16,481 17,668 18,940 20,303 21,765 Multi-Family Potable 3,138 3,364 3,606 3,865 4,144
Commercial
Includes
Institutional/Gover
nmental use type
Potable 6,521 6,990 7,494 8,033 8,612
Landscape Irrigation Potable 3,645 3,907 4,189 4,490 4,813 Sales/Transfers/Excha
nges to other
Suppliers
Metered to San
Joaquin County Potable 998 1,070 1,147 1,230 1,318
Industrial Potable 564 604 648 695 745
Other (optional) Hydrant
Meters/Jumpers Potable 75 80 86 92 99
Distribution System
Water Loss Potable 2,947 3,159 3.387 3,630 3,892
Subtotal Potable 34,368 36,843 39,496 42,339 45,388
Subtotal Non-Potable 0 0 0 0 0
Total 34,368 36,843 39,496 42,339 45,388
It should be noted that population growth does not equate to each sector equally, but in order to maintain conservative water demand, the growth rate was uniformly applied to all sectors. When the DWR’s population tool is updated, the water use projections will be updated to more accurately reflect projected consumption.
4.2.4 Water Use for Lower Income Households
The DWR requires retail water suppliers to include projected water use for lower-income households in their projected water use for the UWMP. Including lower-income projected water use will assist the City in addressing the requirement of Government Code 65589.7, which prioritizes lower income households water needs.
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The City of Stockton’s 2040 General Plan includes its updated Housing Element for 2023-2031. The report classifies 31.7% of the population as low-income households, which is defined as households making less than 80% of the area’s median income of $85,000, adjusted for family size.
Table 4-2 and Table 4-3 have lower income households included in their projections. This is confirmed in Table 4-4 below.
Table 4-4: Inclusion in Water Use Projections (DWR Submittal Table 4-3 Retail) Submittal Table 4-3 Retail: Inclusion in Water Use Projections Water Code Section 10631 (a), 10631 (d)(4)(A), and 10631 (d)(4)(B) Are Future Water Savings Included in Projections?
(Refer to Appendix K of UWMP Guidebook)
Drop down list (y/n)
Yes
If "Yes" to above:
State the section or page number, in the cell to the right, where citations of the codes, ordinances, or otherwise are utilized in demand projections are found.
OPTIONAL Suppliers may complete Optional Submittal Table 4-4 R to quantify the expected savings.
California Code of
Regulations, Title 23
Waters, Division 2 DWR,
Chapter 2.7 Model Water
Efficient Landscape
Ordinance (MWELO),
updated 2015
Are Lower Income Residential Demands Included In Projections? (Refer to Appendix K of UWMP Guidebook)
Drop down list (y/n)
Yes
OPTIONAL If the method for accounting Lower Income Residential Demands has been included, provide page number where this accounting can be found. (An example is included in Appendix K.) n/a
Using projected water use data from Table 4-3, and the information from the City’s updated Housing Element, it is estimated that approximately 6,300 AF will be allocated to lower income households in the year 2050.
4.3 Estimated Future Water Savings
Water savings from codes, standards, ordinances, or transportation and land use plans can decrease water use and are allowed to be incorporated into COSMUD’s demand projections. As of 2020, COSMUD was able to reduce their water consumption by 20% as outlined in Chapter 5 of this UWMP. This conservation was accomplished via public outreach campaigns as well as an adherence to MWELO standards to decrease irrigation water use. Until May 21, 2024, the City was in a Stage 2 Water Shortage Emergency but has since downgraded to a Stage 1 Water Shortage Emergency. This EXHIBIT 1
4 Water Use Characterization 2025 UWMP
4-21
enforces Stockton Municipal Code (SMC) 13.28 Water Conservation Guidelines, which include the following:
• Outdoor watering is only allowed between 6:00pm and 8:00pm on the following days:
o Sunday/Wednesday for addresses ending in 0, 2, 4, 6, or 8 o Tuesday/Saturday for addresses ending in 1, 3, 5, 7, or 9 • Wash vehicles with a hose that has a shutoff nozzle or similar device, or at a car wash that uses recycled water.
• No watering non-functional turf at commercial, industrial, and institutional properties. • No watering outdoor landscapes during and within 48 hours after measurable rainfall. • No using running water to clean driveways, sidewalks, or other paved areas, unless for health and safety purposes.
As COSMUD has implemented MWELO practices for the entirety of this updated UWMP, the water savings has been incorporated into data found in Table 4-2 for water use projections; therefore, the data reflects these passive savings in the future.
The SMC Chapters 13.28 (Water Conservation) and 13.32 (Water Storage Emergencies) is included in Attachment H.
4.4 Distribution System Water Loss
Water system losses are divided into two categories – apparent losses and real losses. Apparent losses are made up of systematic data handling errors, customer metering inaccuracies, and unauthorized consumption. Real losses are made up of physical water losses within the water system. Real water losses include leaks, breaks, and overflows. Real losses can be exacerbated by a lengthened duration of each leak, break, or overflow.
COSMUD has reported the water system losses to the DWR Water Loss Audit Program for the five (5) years leading up to 2025, as shown in Table 4-5. COSMUD’s water loss audit data transitioned from the calendar year to fiscal year beginning in July 2021. Due to this transition, there is a gap in audit data for the first half of 2021.
EXHIBIT 1
4 Water Use Characterization 2025 UWMP
4-22
Table 4-5: Water Loss Audit Reporting (DWR Submittal Table 4-5 Retail) Submittal Table 4-5 Retail: Water Loss Audit Reporting
Water Code Section 10631(d)(3)(A)
Public Water System ID #
Reported in Table 2-1 R Reporting Period
Submitted to DWR Water
Loss Audit Program
(yes/no)
Report submittal status for all five years for each Public Water System as available.
Add rows as needed
2020 Yes
2021 Yes
2022 Yes
2023 Yes
2024 Yes
NOTES: Gap in water loss audit data from 1/1/21 to 6/30/21 2020 audit data:
Stockton City of - Validated Water Audit 2020.xlsx
2021/2022 audit data:
City of Stockton FY2022 - Validated Audit.xlsx
2022/2023 audit data:
City of Stockton FY2023 Validated Audit.xlsx
2023/2024 audit data:
City of Stockton FY2024 Water Loss Audit Validated.xlsx 2024/2025 audit data:
City of Stockton FY2025 - Validated Audit.xlsx
Water Use Efficiency (WUE) standards were developed for each urban retail water supplier in California serving more than 3,000 connections or that produce more than 3,000 AF of water per year. These standards are tailored to each agency based on current and historic losses, with all agencies required to meet their standard by January 1, 2028. As of the most recent AWWA Water Loss Audit submitted to DWR, the COSMUD service area consists of 51,730 connections. Based on 2025 AWWA Water Loss Audit Data, COSMUD will need to reduce their real water loss from 17.4 Gallons per Service Connection per Day (GPSCD) to 16.5 GPSCD, which is approximately a 5.5% reduction in real losses within the next two years. COSMUD is currently surpassing their apparent water loss standard set by the State Water Board, with apparent losses currently at 10.3 GPSCD with the standard having been set at 11.7 GPSCD, which 12% below of the 2028 Standard. The most recent data for progress towards the WUE standards are outlined in Table 4-6.
EXHIBIT 1
4-Water Use Characterization 2025 UWMP
4-1
Table 4-6: Progress Towards 2028 Water Loss Standard (Table 4-6 Retail) Submittal Table 4-6 Retail: Progress Towards 2028 Water Loss Standard Water Code Section 10631(d)(3)(C) Public Water
System ID #
Reported in
Submittal
Table 2-1 R
Did the
Water Board
Calculate a
Water Loss
Standard for
this Public
Water
System?
(y/n)
If no,
Supplier will
not
complete
this row.
Real Water Loss Apparent Water Loss
State Water Board
Standard
Most Recent AWWA Water
Loss Audit
Real Water
Loss Per Unit
per Day
State Water Board Standard Most Recent AWWA Water Loss Audit Apparent Water
Loss Per Unit per
Day
2028
Real
Water
Loss
Standard
per Unit
per day
Units for
Real Water
Loss
Drop down
list
Number of
Units
(Connections
or Miles
corresponding
with units
selected)
Volume of
Total Real
Loss (from
AWWA Water
Loss Audit)
2028 Apparent
Water Loss
Standard per
Unit per Day
Units for
Apparent
Water Loss
Number of
Connections
Volume of
Total
Apparent
Loss
(from
AWWA
Water Loss
Audit)
(AF)
(AF)
Add additional rows as needed.
CA3910012 Yes 16.5
Gallons per
Service
Connection
per Day
(GPSCD)
51,730 1,007.8 17.4 11.7
Gallons per
Service
Connection
per Day
(GPSCD)
51,730 597.4 10.3
EXHIBIT
1 4-Water Use Characterization 2025 UWMP
4-1
4.5 Data Provided to Wholesale Agency – To Be Developed in Future Submittal
4.6 Climate Change
In 2025, the City of Stockton published the Stockton Metropolitan Statistical Area Priority Climate Action Plan (PCAP) under the U.S. Environmental Protection Agency’s (EPA) Climate Pollution Reduction Grants Program. The document establishes a plan to reduce greenhouse gas emissions, enhance climate resilience, and advance equitable benefits for all communities in San Joaquin County.
The PCAP identifies climate change as a leading cause of potential water-related challenges in the Stockton region as climate conditions become more extreme and less predictable. Potential challenges include both increased flood conditions through heavy storms and reduced water availability through longer and more frequent droughts as the climate changes. As water drought conditions increase, there could be an increased reliance on groundwater, raising costs for the community.
Solutions proposed in the PCAP to mitigate impacts on potable water due to climate change include protecting wetlands and natural systems to help absorb floodwaters and buffer storm impacts, addressing saltwater intrusion risks in the Bay-Delta by protecting levees and managing groundwater resources, implementing drought-tolerant landscaping, and implementing water efficiency/conservation practices in the area.
EXHIBIT 1
5-1
CHAPTER 5 – SB X7-7 BASELINES, 2020 TARGETS, AND
2025 REPORTING
5 SB X7-7 Baselines, 2020 Targets, and 2025 Reporting
The Water Conservation Act, or Senate Bill X7-7, requires all water suppliers to implement water efficiency measures that will reduce their per-capita water consumption for both urban and agricultural uses. This statewide legislation sought to reduce per-capita water consumption by 20% by 2020.
For the development of COSMUD’s 2020 UWMP, the City’s individual target of compliance was assessed to determine whether the SBX7-7 goal was met. The following section details COSMUD’s compliance with the 2020 water use target.
5.1 Compliance with 20% by 2020 Water Use Target
As part of the 2015 UWMP, retail suppliers identified their 2020 demand reduction targets with one of four methods identified in SBX7-7:
Target Method 1: 80% of 10- to 15-year baseline gallons per-capita per day (GPCD).
Target Method 2: The sum of the following performance standards:
• Indoor residential use
• Landscape use, including dedicated and residential meters or connections equivalent to the State Model Landscape Ordinance (70% of reference evapotranspiration) • 10% reduction in baseline commercial, industrial institutional (CII) water use by 2020.
Target Method 3: 95% of Hydrologic Regional Target from the 20% by 2020 Water Conservation Plan Target Method 4: Identify water savings obtained through approved practices and subtract them from the baseline GPCD.
Target Method 3 was used for calculating COSMUD’s 2020 water use target. Table 5-1 outlines the SBX7-7 Target GPCD and the actual 2020 GPCD.
EXHIBIT 1
5-SB X7-7 Baselines, 2020 Targets, and 2025 Reporting 2025 UWMP 5-2
Table 5-1: SB X7-7 2020 Target Progress (DWR Submittal Table 5-1 Retail) Submittal Table 5-1 Retail: SB X7-7 2020 Target Progress Water Code Section 10608.40 Check the box if the Supplier was not an Urban Water Supplier during or before the 2020 UWMP reporting cycle. Proceed to the next table.
Was Supplier part of
a merger or
consolidation since
2020?
Regional Alliance
Target or
Individual Target?
Drop down list
2020
Target
Actual 2020
GPCD
Did Supplier Achieve
Targeted Reduction
for 2020?
Only for suppliers that did not
meet the Target in 2020
See DWR NOTES below.
Actual 2025
GPCD
(From SB X7-7
Compliance
Form)
Did Supplier meet
the 2020 Target in
2025?
No Individual Target 165 158 Yes NA
NOTES:
The 2025 UWMP does not have any new statutory requirements. COSMUD was able to obtain their targeted reduction by 2020 and no further reporting requirements are necessary.
EXHIBIT
1 6-1
CHAPTER 6 – WATER SERVICE RELIABILITY AND
DROUGHT RISK ASSESSMENT
6 Water Service Reliability and Drought Risk Assessment This chapter summarizes the City’s current and future water supply portfolio, how individual supplies are managed conjunctively, and how climate change and regulatory factors may affect availability. It also reports the energy intensity associated with treating and delivering water within the COSMUD service area.
6.1 Reliability Assessment Approach
The reliability assessment characterizes the City’s existing and planned water supplies and evaluates their ability to meet projected demands under a range of hydrologic conditions, consistent with the requirements of the Urban Water Management Planning Act and guidance provided in the Draft 2025 Urban Water Management Plan Guidebook. The City’s water supply portfolio and long-term planning assumptions are primarily informed by the 2021 City of Stockton Water Master Plan Update, which serves as the City’s adopted engineering and operational framework for water system planning. The 2026 Well Technical Memo also serves as an important reference to inform recent groundwater supply updates since the Water Master Plan. This UWMP provides a planning-level summary of water supply, operations, and reliability for regulatory review.
6.2 Service Area and Supply Overview
The City provides potable water service to customers within the City limits and surrounding areas through COSMUD. The City operates a diversified, conjunctive use water supply portfolio comprised of surface water, groundwater, and purchased water supplies to meet potable water demands throughout its service area. Primary surface water sources include direct diversions from the San Joaquin River under the City’s water rights, as well as purchased treated surface water from SEWD. In addition, the City purchases untreated surface water from the WID, which is conveyed to the Delta Water Treatment Plant for treatment prior to distribution within the potable water system.
Groundwater extracted from municipal production wells within the Eastern San Joaquin Groundwater Basin provides a critical supplemental supply and serves as the City’s primary drought response resource during dry and multiple dry year conditions. While the City does not operate a dedicated non‑potable recycled water distribution system, treated wastewater discharges contribute to indirect potable reuse by augmenting surface water availability in the San Joaquin River in accordance with applicable regulatory requirements.
Collectively, these water supply sources are operated under the City’s adopted conjunctive use strategy to enhance system reliability, provide operational flexibility, and reduce vulnerability to hydrologic EXHIBIT 1
6 Water Service Reliability and Drought Risk Assessment 2025 UWMP 6-2
variability, regulatory constraints, and long‑term demand growth. Figure 6-1 depicts the City’s existing surface water supply sources and their respective connections to the distribution system.
EXHIBIT 1
EXHIBIT 1
6 Water Service Reliability and Drought Risk Assessment 2025 UWMP 6-4
6.3 Surface Water Supplies
Surface water is the City’s primary source of supply during normal and wet hydrologic conditions. Raw water is diverted from the San Joaquin River and conveyed to the City’s treatment facilities, where it is treated to meet all applicable state and federal drinking water standards.
6.3.1 San Joaquin River Diversion
The City is authorized to divert surface water from the San Joaquin River for municipal use under Water Right Permit No. 21176. Raw water diverted from the river is conveyed to the City’s Delta Water Treatment Plant, where it is treated to meet applicable drinking water standards prior to distribution within the potable water system. The San Joaquin River diversion represents a core component of the City’s local surface water supply portfolio and is operated in coordination with wastewater discharge requirements.
The availability of San Joaquin River supplies is influenced by hydrologic conditions, Delta water quality, and regulatory requirements governing river operations and environmental protections. As documented in the City’s 2021 Water Master Plan, this supply is managed as part of an integrated surface water system that balances diversion operations with treatment plant capacity and system demands. During periods when surface water diversion is constrained due to seasonal, hydrologic, or regulatory conditions, the City relies on alternative surface water sources and groundwater supplies to maintain potable water service reliability.
In 1996, the City submitted a water right application to the State Water Resources Control Board (State Water Board) requesting authorization to divert up to 125,900 acre‑feet per year (AFY) from the San Joaquin River to meet projected long‑term demands through 2050. The State Water Board divided the application into two separate applications, Application 30531A and Application 30531B.
Application 30531A authorized diversions of up to 33,600 AFY from the San Joaquin River for use within the City’s 1990 General Plan boundary and was approved under Water Right Permit 21176, issued on March 8, 2006, pursuant to California Water Code (CWC) Section 1485. Under this permit, allowable diversions are limited to the volume of treated wastewater discharged by the City to the San Joaquin River as part of an indirect potable reuse strategy, with a maximum permitted diversion of 33,600 AFY.
Diversions under Section 1485 are subject to seasonal and environmental pumping restrictions.
Application 30531B, which proposes additional diversions of up to 92,300 AFY, has been canceled by the State. The City intends to pursue area of origin water rights per water code section 10500-10506.
EXHIBIT 1
6 Water Service Reliability and Drought Risk Assessment 2025 UWMP 6-5
6.3.2 Stockton East Water District
The City purchases treated potable water from SEWD as part of its surface water supply portfolio. SEWD supplies originate from New Melones Reservoir on the Stanislaus River and New Hogan Reservoir on the Calaveras River and are treated prior to being delivered directly into the City’s distribution system.
SEWD is a wholesale water supplier serving urban water retailers within the Stockton Metropolitan Area, including the City, Cal Water, and two small maintenance districts, and provides irrigation water to agricultural users in San Joaquin County. SEWD’s surface water supplies are obtained under agreements with the U.S. Bureau of Reclamation, and the District has filed additional water right applications to divert excess wet‑weather flows from the Calaveras River, Little Johns Creek, and other tributaries, which are currently under review by the State Water Resources Control Board. From 1977 to 2012, SEWD was the sole provider of treated surface water to COSMUD and supplied a substantial portion of its total water demand. The South Stockton service area currently receives water from both SEWD and groundwater sources. In 2020, approximately 7,000 AF of water supplied by SEWD accounted for about 20 percent of COSMUD’s total supply.
Operation of the DWTP beginning in 2012 provided COSMUD with a reliable surface water supply under Water Right Permit 21176 for use throughout its service area. COSMUD will continue to receive SEWD water under the Second Amended Contract, which expires in 2035 and provides for continued service under then-current or mutually agreeable terms. In North Stockton, completion of the North Stockton Pipeline Hypochlorite Facility in 2021 enables integration of DWTP and SEWD supplies, allowing increased SEWD deliveries and reduced groundwater pumping during peak demand periods. The City’s Contract is SWED is included in Attachment F.
6.3.3 Woodbridge Irrigation District
The City of Stockton purchases untreated surface water from the WID as part of its surface water supply portfolio. WID diverts surface water from the Mokelumne River under pre‑1914 water rights at the Woodbridge Diversion Dam, which impounds Lodi Lake, with additional authorized diversions from hydraulically connected sloughs within the Mokelumne River system, including Pixley Slough and Beaver Slough. Water delivered by WID to the City is conveyed to the Delta Water Treatment Plant, where it is treated prior to distribution. Under a 2008 agreement with the Woodbridge Irrigation District (WID), additional surface water supplies become available to the City as WID‑served agricultural lands within the northern portion of the City are annexed and converted to residential and industrial use. The agreement provides for an incremental increase in WID supply at a rate of 3.0 acre‑feet per year (AFY) per acre annexed, allowing up to 6,500 AFY of additional supply to become available to the City. Based on anticipated annexation and land use conversion, total WID supplies available to the City could increase from 6,500 AFY to approximately 9,500 AFY by 2035.
EXHIBIT 1
6 Water Service Reliability and Drought Risk Assessment 2025 UWMP 6-6
WID supplies supplement the City’s local surface water diversions and contribute to overall surface water availability, particularly during periods when San Joaquin River diversions are limited. As noted in the City’s 2021 Water Master Plan, WID water serves an important operational role within the City’s integrated surface water system by supporting reduced reliance on groundwater pumping during normal hydrologic conditions. Accordingly, this supply also contributes to regional groundwater sustainability by offsetting the need for increased groundwater extraction.
Unused entitlements may be banked under specific conditions, including delays in the City’s Delta Water Supply Project startup or dry-year curtailments. Banked water is subject to availability as determined by WID, is limited to 2,000 AFY delivery, and generally expires after eight years if unused. The City’s Contract with WID is included in Attachment G.
6.4 Groundwater Supplies
6.4.1 Groundwater Sources
The City’s groundwater supply is derived from 12 active municipal production wells located in the Eastern San Joaquin Groundwater Basin, which underlies both the North Stockton and South Stockton service areas. Groundwater is extracted through a system of COSMUD‑owned wells distributed across the service area and is treated as needed to meet applicable drinking water standards prior to delivery to customers. This basin is the same groundwater source identified and described in the City’s prior Urban Water Management Plans and the 2021 Water Master Plan, and it remains a key component of the City’s conjunctive‑use water supply portfolio.
The City coordinates groundwater management with regional partners through participation in basin‑wide groundwater sustainability planning efforts, consistent with applicable State requirements.
Groundwater use is managed to balance supply reliability, water quality considerations, and long‑term basin sustainability. Figure 6-2 below depicts all active groundwater wells within the service area.
EXHIBIT 1
EXHIBIT 1
6 Water Service Reliability and Drought Risk Assessment 2025 UWMP 6-8
6.4.2 Operational Role of Groundwater
Groundwater serves both as a supplemental and reliability supply within the City’s water system. Under normal operating conditions, groundwater is used conjunctively with surface water supplies to meet system demands, manage peak usage, and provide operational flexibility. During dry years, emergency events, or periods when surface water supplies are constrained or unavailable, groundwater plays a critical role in maintaining water service reliability.
As documented in prior Urban Water Management Plans, the City does not rely on continuous maximum groundwater pumping under normal conditions. Instead, groundwater capacity is preserved to support drought response, emergency operations, and system resiliency.
6.4.3 Updated Groundwater System Condition and Capacity After adopting the 2021 Water Master Plan, the City experienced an operational event in summer 2024 during which both surface water treatment sources—the Delta Water Treatment Plant and Stockton East Water District supplies—were temporarily unavailable at the same time. During this period, the City relied exclusively on groundwater facilities, highlighting the importance of groundwater system conditions and redundancy.
In response, the City commissioned a Water Supply Redundancy Evaluation prepared by West Yost Associates and completed in January 2026, which provides the most current assessment of groundwater well status and capacity. The 2026 Water Supply Evaluation Technical Memo evaluated the current condition of the City’s groundwater well facilities, including capacity, age, and rehabilitation potential to establish potential opportunities for system reliability and cost efficiency. Table 6-1 below summarizes active and inactive wells outlined in the Water Supply Redundancy Evaluation, and a copy is included in Attachment E. The evaluation updated well capacities and operational status based on a March 2025 well rehabilitation status review and found that:
• Total active groundwater capacity has decreased slightly since the 2021 Water Master Plan, particularly in North Stockton, due to several wells becoming inactive or requiring mechanical repair or treatment.
• In South Stockton, active groundwater capacity remains generally consistent with levels reported in prior planning documents. Several inactive or standby wells were evaluated for rehabilitation potential, with only a limited number identified as viable candidates based on age, site constraints, and water quality considerations. Table 6-2 lists the volume of groundwater pumped in the previous 5 years.
EXHIBIT 1
6 Water Service Reliability and Drought Risk Assessment 2025 UWMP 6-9
Table 6-1: Summary of Well Facilities
Summary of Well Facilities
Well Number Well Pump Capacity (gpm) Status
03R 2,000 Active
10R 3,200 Active
15 1,805 Standby
18 800 Active
19 1,780 Active
20 1,800 Inactive
21 1,800 Active
24 430 Inactive
25 1,600 Inactive
26 1,970 Inactive
27 2,200 Active
28 1,600 Standby
29 2,500 Active
30 2,200 Standby
31 2,000 Active
32 2,000 Active
SS1 1,000 Inactive
SS2 1,295 Standby
SS3 2,000 Active
SS8 1,500 Active
SS9 2,500 Active
Note: Wells 11, 16, SS4, and SS5 are omitted from the 2026 Technical Memo and will be included upon further coordination with COSMUD.
EXHIBIT 1
6 Water Service Reliability and Drought Risk Assessment 2025 UWMP 6-10
Table 6-2: Volume of Groundwater Pumped in Past Five Years (DWR Table 6-1 Retail) Submittal Table 6-1 Retail: Groundwater Volume Pumped
Water Code Section 10631(4) and 10631(4)(c)
Check the box if the Supplier does not pump groundwater.
Proceed to the next table.
Check the box if all or part of the groundwater described below is desalinated. (OPTIONAL)
Groundwater Type
Drop Down List
May use each category multiple
times
Water Type
(OPTIONAL)
Drop down list
Location or Basin
Name
2021 2022 2023 2024 2025
(AF) (AF) (AF) (AF) (AF)
Add additional rows as needed
Alluvial Basin Non-Potable
San Joaquin Valley Basin,
Eastern San Joaquin
Subbasin
7089 1547 2430 1066 956
Total 7,089 1,547 2,430 1,066 956
6.4.4 Groundwater Reliability and Planning Considerations The groundwater capacity assessment performed by West Yost Associates utilizes a conservative planning scenario approach and assumes complete loss of surface water supplies, representing an emergency or redundancy condition rather than typical system operation. Under this groundwater‑only scenario, existing groundwater capacity is not sufficient to meet maximum‑day demands without additional well rehabilitation or new well construction.
This finding does not conflict with the conclusions of the 2020 UWMP or the 2021 Water Master Plan, which determined that overall water supplies are sufficient to meet future demands under normal, single‑dry, and multiple‑dry year conditions using a conjunctive‑use approach. Instead, the evaluation highlights a separate resiliency consideration: the level of investment required to maintain service during rare but critical events involving simultaneous surface water outages.
For this 2025 UWMP, groundwater continues to be characterized as a reliable supplemental supply that supports system resiliency when integrated with surface water supplies. Long‑term planning for groundwater improvements, including rehabilitation, new wells, and treatment, is addressed through the City’s master planning and capital improvement processes rather than relied upon as an assumption for routine water supply availability.
EXHIBIT 1
6 Water Service Reliability and Drought Risk Assessment 2025 UWMP 6-11
6.5 Water Supply Data (Past Five Years)
To characterize recent operational use of the City’s water supply portfolio, Table 6-3 summarizes total water supplied over the most recent five‑year period from the City’s four primary sources: Municipal groundwater wells, SEWD, San Joaquin River diversions, and WID. Reviewing recent supply trends is important because it reflects actual system operations, hydrologic conditions, and regulatory or infrastructure constraints. The accompanying Figure 6-3 illustrates the relative contribution of each source over this period, highlighting shifts in reliance among surface water, purchased supplies, and groundwater consistent with the City’s conjunctive‑use strategy.
Table 6-3: Total Water Supply per Year (AFY)
Total Supply per Year (AFY)
Year COSMUD Wells SEWD San Joaquin WID Total
2020 8,635 6,762 9967 8,657 34,021
2021 7,089 7,579 14,447 5,038 34,152
2022 1,548 16,207 7,204 7,035 31,994
2023 2,432 12,558 5,967 9,591 30,548
2024 1,066 17,239 6,134 7,016 31,456
2025 956 16,571 4,910 9,341 31,778
Figure 6-3: Percent Water Supply by Source
While the Water Supply Redundancy Evaluation discussed in Section 6.4.3 found a slight decrease in active groundwater capacity, the recent increase in purchased potable water from SEWD and decrease in groundwater pumping is more readily explained by the City’s adopted conjunctive-use strategy, which deliberately prioritizes surface water in normal years and reserves groundwater as a drought and EXHIBIT 1
6 Water Service Reliability and Drought Risk Assessment 2025 UWMP 6-12
reliability supply rather than a base supply. It also reflects an effort to reduce long-term basin impacts, and improved water use efficiency and conservation.
6.6 Other Water Supplies
In addition to surface water and groundwater, the City continues to evaluate opportunities to enhance supply reliability through:
• Operational storage and system optimization,
• Water use efficiency and demand management programs, and • Long-term planning studies identified in the Water Master Plan.
While recycled water, desalination, and water transfers are not primary potable supply sources at this time, the City monitors regulatory developments and regional opportunities that could affect future supply portfolios, as discussed in both the 2021 Water Master Plan and the 2020 UWMP.
6.6.1 Wastewater Collection
COSMUD provides regional wastewater collection, treatment, and disposal services for the City of Stockton, the Port of Stockton, and surrounding urbanized areas of San Joaquin County. Wastewater is conveyed to the Regional Wastewater Control Facility (RWCF), where it is treated to tertiary standards and discharged to the San Joaquin River.
Under Water Right Permit 21176, issued by the State Water Resources Control Board on March 8, 2006, the City is authorized to divert water from the San Joaquin River pursuant to California Water Code Section 1485, up to 33,600 acre‑feet per year, limited to the volume of treated wastewater discharged to the river. This authority supports the City’s indirect potable reuse program, which relies on coordinated RWCF discharges and Delta Water Treatment Plant diversions rather than a dedicated recycled water distribution system. Although the RWCF produces tertiary‑treated effluent suitable for unrestricted non‑potable reuse, recycled water is not delivered directly to customers. Table 6-4- below shows the volume of wastewater collected within the service area.
EXHIBIT 1
6 Water Service Reliability and Drought Risk Assessment 2025 UWMP 6-13
Table 6-4-: Wastewater Collected Within Service Area in 2025 (DWR Table 6-2 Retail) Submittal Table 6-2 Retail: Wastewater Collected Within Service Area in 2025 Water Code Section 10633(a)
Check the box if there is no wastewater collection system.
Proceed to the next table.
Wastewater Collection Recipient of Collected Wastewater Name of Wastewater
Collection Agency
Wastewater
Volume
Metered or
Estimated?
OPTIONAL
Drop Down List
Volume of
Wastewater
Collected
from UWMP
Service Area
2025
Name of Wastewater
Treatment Plant (WWTP)
and Place ID Number
Drop down list
Is WWTP
Located
Within UWMP
Area?
Drop Down List
(AF)
Add additional rows as needed
COSMUD Metered 10,894
Stockton Regional WW
Control Facility, Place ID
258739
Yes
Total Wastewater Received from UWMP
Service Area in 2025: 10,894
NOTES: Units are in acre-feet (AF). Collected wastewater volume includes that which is produced by Cal Water and San Joaquin County service areas since they are not metered separately.
Table 6-5 below displays the volume of wastewater treated and discharged in 2025 within the COSMUD water service area provided.
EXHIBIT 1
6 Water Service Reliability and Drought Risk Assessment 2025 UWMP 6-14
Submittal Table 6-3 Retail: Wastewater Treatment and Outcomes Within UWMP Service Area in 2025 Water Code Section 10633(a) Wastewater
Treatment Plant
Name and Place
ID Number
Does This
Plant Treat
Wastewater
Generated
Outside the
UWMP
Service Area?
(OPTIONAL)
2025 Volume
of
Wastewater
Received
from UWMP
Service Area
(As Reported
in Submittal
Table 6-2 R)
Total
2025
Volume
of Water
Treated
2025 Outcomes of Treated Wastewater
Water
Recycled
Within UWMP
Service Area
(enter data as
applicable)
Water
Recycled
Outside of
UWMP Service
Area
(enter data
as
applicable)
Effluent
Discharge
that is not a
Permitted
Recycled
Water Use
(enter data
as
applicable)
Required
Discharge
for
Instream
Flow
(enter data
as
applicable)
Delivered to Another Entity for Additional Treatment
(enter data as applicable)
Treatment
Level
Volume
Treatment
Level
Volume
Treatment
Level
Volume
Treatment
Level
Volume
Treatment Level
Volume
Name of
other entity
(AF) (AF) (AF) (AF) (AF) (AF) (AF)
Stockton Regional
WW Control
Facility, Place ID
258739
Yes 11,077 9,413 Non- Potable 4,910 0 0 0
Total 11,077 9,413 0 4,910 0 0 0
NOTES: Units are in acre-feet (AF). Volumes of treated wastewater and discharged wastewater are provided by Wastewater Operations QOR Sharepoint.
Table 6-5: Wastewater Treatment and Discharge Within Service Area in 2025 (DWR Table 6-3 Retail)
EXHIBIT
1 6 Water Service Reliability and Drought Risk Assessment 2025 UWMP 6-15
6.6.2 Recycled Water
The 2020 UWMP did not indicate any recycled water use projections; however, Table 6-7 below shows the City does has one source of recycled water in the form of indirect potable reuse. The quantity of water discharged from the wastewater treatment plant can be recaptured and recycled as needed, resulting in approximately 30,000 AF of water over the next 25 years.
Table 6-6: Recycled Water Direct Beneficial Use Within Service Area (DWR Table 6-4 Retail) Submittal Table 6-4 Retail: Recycled Water Direct Beneficial Uses Within Service Area Water Code Section 10633 (c)(e)
Check box if recycled water is not used and is not planned for use within the service area of the supplier. The supplier will only complete the column on "Potential Recycled Water Use" and submit an accompanying narrative on the feasibility of that potential recycled water use.
Use Type
Drop down list
Water
Type
(after
treatment
if treated)
(OPTIONAL
)
Drop down
list
Additional
Informatio
n
(as
needed)
2025 2030 2035 2040 2045
2050
(opt)
Potential Recycled
Water Use
(AF) (AF) (AF) (AF) (AF) (AF) Volume
Narrative
page
number
(OPTIONAL)
Add additional rows as needed
Agricultural irrigation - - - - - - - -
Landscape irrigation (exc golf
courses) - - - - - - - -
Golf course irrigation - - - - - - - -
Commercial use - - - - - - - -
Industrial use - - - - - - - -
Geothermal and other energy
production - - - - - - - -
Recreational impoundment - - - - - - - -
Wetlands or wildlife habitat - - - - - - - -
Groundwater recharge (IPR) - - - - - - - -
Reservoir water
augmentation (IPR) - - - - - - - -
Indirect potable reuse 4,910 5,000 5,000 5,000 5,000 5,000 29,910 - Other (Description Required) - - - - - - - -
Total 0 0 0 0 0 0 0 0
EXHIBIT 1
6 Water Service Reliability and Drought Risk Assessment 2025 UWMP 6-16
Table 6-7: 2020 Recycled Water Use Projection and 2025 Actual Use (DWR Table 6-5 Retail) Submittal Table 6-5 Retail: 2020 UWMP Recycled Water Use Projection Compared to 2025 Actual Water Code Section 10633 (e)
Check the box if recycled water was not used in 2025 nor previously projected for use in 2020.
Proceed to the next table.
Use Type
Drop Down list
2020 Projection for
2025 2025 Actual Use
(AF) (AF)
Add additional rows as needed
Agricultural irrigation - -
Landscape irrigation (exc golf courses) - -
Golf course irrigation - -
Commercial use - -
Industrial use - -
Geothermal and other energy production - -
Seawater intrusion barrier - -
Recreational impoundment - -
Wetlands or wildlife habitat - -
Groundwater recharge (IPR) - -
Reservoir water augmentation (IPR) - -
Indirect potable reuse - 4,910
Other (Description Required) - -
Total 0 4,910
Table 6-8 shows that the City does not plan to expand recycled water use in the future.
Table 6-8: Methods to Encourage Future Recycled Water Use (DWR Table 6-6 Retail) Submittal Table 6-6 Retail: Methods to Encourage Future Recycled Water Use Water Code Section 10633 (f)
Check the box if the Supplier does not plan to expand recycled water use in the future. Supplier will not complete the table below but will provide narrative explanation.
Name of Action Description
Planned
Implementatio
n Year
Expected Increase in Recycled Water
Use
(AF)
Add additional rows as needed
Total (AF) 0
6.7 Water Supply Reliability Projects
COSMUD water demands are expected to grow over the next 25 years, and to accommodate this growth while maintaining reliable service, the City will continue to advance the water supply initiatives identified in the previous UWMP. The initiatives outlined in Table 6-9 below are intended to enhance supply flexibility, improve reliability, and ensure efficient use of available resources.
EXHIBIT 1
6 Water Service Reliability and Drought Risk Assessment 2025 UWMP 6-17
Table 6-9: Expected Future Water Supply Projects or Programs (DWR Table 6-7 Retail) Submittal Table 6-7 Retail: Expected Future Water Supply Projects or Programs Water Code Section 10631 (f)
Check the box if there are no expected future water supply projects or programs that provide a quantifiable increase to the agency's water supply.
Procees to the next table.
Check the box if some or all of the supplier's future water supply projects or programs are not compatible with this table and are described in a narrative format.
Name of Future Projects or
Programs
Joint Project with other
suppliers?
Additional Description
(as needed)
Water Type
(after
treatment
if treated)
(OPTIONAL)
Drop Down
list
Planned
Implementation Year
Planned
for Use
in Year
Type
Drop
Down
List
Expected
Increase
in
Water
Supply
to
Supplier
(This
may be a
range)
Drop Down
List
(yes/no)
If Yes,
Supplier
Name
(AF)
North Stockton Pipeline
Hypochlorite Facility Project (a) Yes SEWD
Construct new sodium
hypochlorite injection
system to combine
supply from the DWTP
and SEWD
Potable Completed in 2021 All Year
Types
Increase WID Supply (b) Yes WID
Per contract, WID
would supply the City
with an additional 3.0
AFY per acre the City
annexed
NonPotable 2030 All Year
Types
6500
AFY
Advanced Metering
Infrastructure (c) No -
Provide greater
efficiency and reduce
costs for meter reading
and allow customers to
better track and
manage their water use
2025-2028 All Year
Types
Well 30 No Construct new Well 30 Potable TBD TBD 32 AFY Well 33 Borehole No Develop Well 33 Potable TBD TBD 3.4 AFY NOTES: Units are in acre-feet (AF).
(a) The project will increase supply reliability by allowing North Stockton to be supplied by the DWTP and SEWD without formation of undesirable disinfection byproducts due to different potable water treatment processes. (b) WID supply may increase by an additional 6,500 AFY as agricultural lands north of the City are annexed to the City. (c) AMI will provide customers with the ability to access and better manage their water use.
EXHIBIT 1
6 Water Service Reliability and Drought Risk Assessment 2025 UWMP 6-18
6.7.1 Sodium Hypochlorite Facility
After initiating chloramine disinfection in the North Stockton system, COSMUD isolated North Stockton from Stockton East Water District (SEWD) deliveries due to incompatibility between disinfection strategies. SEWD’s DJWWTP uses free chlorine, while the City’s DWTP supplies water treated for chloramination; blending these supplies can contribute to degraded chlorine residual and increased potential for disinfection byproduct formation, with associated taste and odor concerns.
To restore operational flexibility and improve reliability, COSMUD advanced the North Stockton Pipeline Hypochlorite Facility Project to enable conveyance and blending of SEWD and DWTP supplies in North Stockton. The project included installation of a sodium hypochlorite feed system, which was completed in 2021, to increase available chlorine upstream of the existing North Stockton Pipeline Ammonia Facility, supporting stable chloramination and maintaining acceptable residual in blended water while reducing the potential for undesirable byproduct formation.
6.7.2 Land Annexation
The 2020 UWMP outlined a potential increase in WID water supply from 6,500 AFY to 13,000 AFY by the year 2030 due to the nature of the City’s 2008 contract with WID. Since then, the City has acquired an additional 740 acres of land through annexations and reorganizations. As the contract with WID states, every acre of land annexed equates to an additional 3.0 AFY available for the City to purchase – thereby increasing the available water supply from WID to 8,720 AFY.
6.7.3 Advanced Metering Infrastructure (AMI)
COSMUD is actively pursuing implementation of Advanced Metering Infrastructure (AMI) to improve metering efficiency and system operations. COSMUD currently serves 51,887 water meters, which are read using a combination of manual and touch‑read methods. AMI can reduce operational costs, enhance customer service, and support leak detection and consumption awareness; however, no measurable reductions in water demand have been observed to date. Implementing AMI remains an active and ongoing effort.
6.8 Summary of Water Supply Reliability
Combined, the City’s surface water and groundwater sources form a flexible water supply system that can meet projected demands during normal years and help maintain reliability during dry and multiple dry years. Detailed information on supply availability is provided in the UWMP tables and discussed further in Chapter 7.
Table 6-10 and 6-11 below display the existing and projected normal year water supplies, respectively.
Projected water supplies numbers for WID in Table 6-11 have been provided by them directly.
EXHIBIT 1
6 Water Service Reliability and Drought Risk Assessment 2025 UWMP 6-19
Table 6-10: Water Supplies – 2025 Actual (DWR Table 6-8 Retail) Submittal Table 6-8 Retail: Water Supplies — 2025 Actual Water Code Section 10631 (b)
Water Supply
Additional Description
(as needed)
2025
Drop down list
May use each category multiple times. These
are the only water supply categories that will be
recognized by the WUEdata online submittal
tool
Water Type
(after treatment if treated)
(OPTIONAL)
Drop Down list
Actual Volume
(AF)
Purchased or Imported Water SEWD Potable 16,571
Purchased or Imported Water WID Potable 9,341
Surface water (not desalinated) San Jaoquin River Diversion Potable 4,910 Groundwater (not desalinated) City-owned wells Potable 956 Subtotal Potable 31,778
Subtotal Non-Potable 0
Total 31,778
NOTES: Units are in acre-feet (AF).
Table 6-11: Water Supplies – Projected (DWR Table 6-9 Retail) Submittal Table 6-9 Retail: Water Supplies — Projected
Water Code Section 10631 (b)
Water Supply
Additional
Detail on
Water
Supply
Water
Type
(after
treatment if
treated)
(OPTIONAL)
Drop Down
list
Projected Water Supply (Report to the Extent Practicable) Drop down list
May use each category
multiple times. These are
the only water supply
categories that will be
recognized by the
WUEdata online
submittal tool
2030 2035 2040 2045 2050 (opt)
Reasonably
Available
Volume
Reasonably
Available
Volume
Reasonably
Available
Volume
Reasonably
Available
Volume
Reasonably
Available
Volume
(AF) (AF) (AF) (AF) (AF)
Add additional rows as needed
Purchased or
Imported Water SEWD 20,000 20,000 20,000 20,000 20,000
Purchased or
Imported Water WID 8,850 9,850 10,850 11,850 13,000
Surface water (not
desalinated)
San
Joaquin
River
Diversion
24,800 25,000 25,000 25,000 25,000
Groundwater (not
desalinated)
Cityowned
wells
15,400 15,400 15,400 15,400 15,400
Subtotal Potable 0 0 0 0 0
Subtotal Non-Potable 0 0 0 0 0
Total 69,050 70,250 71,250 72,250 73,400
EXHIBIT 1
6 Water Service Reliability and Drought Risk Assessment 2025 UWMP 6-20
6.9 Energy Intensity
Pursuant to CWC §10631.2(a), this UWMP reports on the energy intensity of COSMUD water service for a one‑year period, using readily available data provided by the City. Energy intensity is expressed in kilowatt‑hours per acre‑foot (kWh/AF) and represents the energy used by COSMUD to divert, pump, treat, store, and distribute water within facilities the City owns and operates; energy associated with Stockton East Water District (SEWD) treatment/delivery and Woodbridge Irrigation District (WID) conveyance is not included. For the year 2025, the overall energy required to deliver water throughout the system is estimated to be about 275 kilowatt-hours per acre-foot (kWh/AF). Additional details are provided in Table 6-12 below.
Table 6-12: Energy Intensity (DWR Table O-1B)
Water Delivery Product
drop down list
(If delivering more than one type of
product recommend using Table O-1C)
Retail Potable Deliveries
Only for Water Delivery Products Under
the Urban Water Supplier's Operational
Control
Start Date of Reporting Period 1/1/2025 Sum of All
Water
Management
Processes
Non-Consequential
Hydropower
End Date of Reporting Period 12/31/2025
Is upstream embedded energy in the
values reported?
Units of Measure for Water (AF)
Total Utility
See DWR
NOTES
Hydropower Net
Utility
Volume of Water Entering Process 29,311 - 29,311
Energy Consumed (kWh) 8,065,961 - 8,065,961
Energy Intensity (kWh/AF) 275 - 275
Quantity of Self-Generated Renewable Energy (Solar)
179,887 kWh
Data Quality (Estimate, Metered Data, Combination of Estimates and Metered Data)
Metered Data
Data Quality Narrative:
Energy consumption was provided for the groundwater wells, reservoir pump and booster stations, San Joaquin River intake, and the DWTP.
Narrative:
The water service area is supplied by surface water from the San Joaquin River, purchased water from SEWD and WID, and groundwater from City-owned production wells. An overview of each water supply source is provided in Section 6.3. Energy data summarize monthly energy consumption associated with operation of the Delta Water Treatment Plant (DWTP), groundwater wells, and reservoirs, with limited on-site solar generation at the DWTP.
EXHIBIT 1
7-1
CHAPTER 7 –WATER SUPPLY RELIABILITY AND DROUGHT
RISK ASSESSMENT
7 Water Supply Reliability and Drought Risk Assessment
This chapter evaluates the City’s ability to reliably meet water demands under a range of hydrologic conditions, including normal year, single dry year, and multiple consecutive dry year scenarios. The assessment builds on the water supply characterization presented in Chapter 6 and compares projected supplies and demands to identify potential vulnerabilities. This chapter also includes the City’s Drought Risk Assessment (DRA) and provides the analytical basis for the Water Shortage Contingency Plan described in Chapter 8.
7.1 Purpose and Planning Framework
The water supply reliability assessment evaluates COSMUD’s water service reliability through 2050 by identifying key factors affecting supply and comparing projected supplies and demands under normal, single‑dry, and five‑consecutive‑dry year conditions. This chapter contains reasonable estimates for projected available water supplies and builds off the 2020 UWMP. Results indicate projected supplies are sufficient to meet existing and future demands under normal and dry conditions.
7.2 Water Supply Reliability Assessment
The Water Supply Reliability Assessment evaluates the City’s ability to meet projected water demands under:
• Normal water year conditions – defined as water supplies the City considers available during normal conditions
• Single dry year conditions – defined as the year with the lowest available water supply to the City
• Multiple consecutive dry year conditions – defined as a five-consecutive-year drought where average water supply available is the lowest.
Under normal conditions, surface water supplies are expected to meet most demands, supplemented as needed by groundwater. During dry and multiple dry years, groundwater production increases to offset reduced surface water availability, consistent with the City’s adopted operational strategy.
7.2.1 SEWD Supply Assessment
The reasonably available supplies established in Table 7-21 below result from coordination with SEWD on historically available water supply to establish the supply reliability metrics. The normal available volume given by SEWD was 27,200 AFY.
EXHIBIT 1
7 Water Supply Reliability and Drought Risk Assessment 2025 UWMP 7-2
Table 7-1: Basis of Water Year Data for SEWD (DWR Table 7-1 Retail) Year Type
Base Year
If not using a
calendar year, type
in the last year of
the fiscal, water
year, or range of
years, for example,
water year 2024-
2025, use 2025
Available Supplies if
Year Type Repeats
Check the box if quantification of available supplies is not compatible with this table and is provided
elsewhere in the UWMP.
Location: [insert location from UWMP]
Quantification of available supplies is provided in this table as either volume only, percent only, or both.
Volume Available % of Average Supply
27,200
Average Year 2025 27,200 100%
Single-Dry Year 2020 22,500 83%
Consecutive Dry Years 1st Year 2015 20,983 77%
Consecutive Dry Years 2nd Year 2016 22,649 83%
Consecutive Dry Years 3rd Year 2017 25,778 95%
Consecutive Dry Years 4th Year 2018 27,564 101%
Consecutive Dry Years 5th Year 2019 28,562 105%
7.2.2 WID Supply Assessment
The reasonably available supplies established in Table 7-2 below result from coordination with WID on historically available water supply. WID supplied historical available volumes and aided in determining the supply reliability metrics. The normal available volume given by WID was 8,850 AFY.
EXHIBIT 1
7 Water Supply Reliability and Drought Risk Assessment 2025 UWMP 7-3
Table 7-2: Basis of Water Year Data for WID (DWR Table 7-1 Retail) Year Type
Base Year
If not using a
calendar year, type
in the last year of
the fiscal, water
year, or range of
years, for example,
water year 2024-
2025, use 2025
Available Supplies if
Year Type Repeats
Check the box if quantification of available supplies is not compatible with this table and is provided
elsewhere in the UWMP.
Location: [insert location from UWMP]
Quantification of available supplies is provided in this table as either volume only, percent only, or both.
Volume Available % of Average Supply
8,850
Average Year 2021 8,850 100%
Single-Dry Year 2020 4,080 46%
Consecutive Dry Years 1st Year 2020 4,080 46%
Consecutive Dry Years 2nd Year 2021 7,993 90%
Consecutive Dry Years 3rd Year 2022 4,760 54%
Consecutive Dry Years 4th Year 2023 4,628 52%
Consecutive Dry Years 5th Year 2024 9,913 112%
7.2.3 San Joaquin River Supply Assessment
Under CWC Section 1485, Water Right Permit 21176 authorizes diversion from the San Joaquin River in an amount equal to the City’s wastewater treatment plant discharge, up to 33,600 AFY, subject to seasonal pumping restrictions due to environmental constraints. The Permit 21176 Petition for Extension of Time (Appendix H in the 2020 UWMP) summarizes water available for diversion from 2012 through 2040 based on wastewater discharge and applicable ESA pumping restrictions. Because the Petition was completed prior to 2020, volumes for 2020–2040 represent projected availability.
Base‑year San Joaquin River water supply availability is summarized in Table 7‑3.
EXHIBIT 1
7 Water Supply Reliability and Drought Risk Assessment 2025 UWMP 7-4
Table 7-3: Basis of Water Year Data for the San Joaquin River (DWR Table 7-1 Retail) Year Type
Base Year
If not using a
calendar year, type
in the last year of
the fiscal, water
year, or range of
years, for example,
water year 2024-
2025, use 2025
Available Supplies if
Year Type Repeats
Check the box if quantification of available supplies is not compatible with this table and is provided
elsewhere in the UWMP.
Location: [insert location from UWMP]
Quantification of available supplies is provided in this table as either volume only, percent only, or both.
Volume Available % of Average Supply
19,900
Average Year 2012-2019 19,900 100%
Single-Dry Year 2014 18,150 91%
Consecutive Dry Years 1st Year 2012 18,300 92%
Consecutive Dry Years 2nd Year 2013 19,000 95%
Consecutive Dry Years 3rd Year 2014 19,000 95%
Consecutive Dry Years 4th Year 2015 18,100 91%
Consecutive Dry Years 5th Year 2016 21,300 107%
7.2.4 City of Stockton (COS) Groundwater Wells
The reasonably available supplies established in Table 7-4 are assumed to remain the same during wet and dry seasons. Following the calculations provided in the 2020 UWMP, multiplying the approximate size of the water service area, 38,500 acres, by an assumed pumping rate of 0.4 ac-ft/acre/year results in a reasonably available volume of 15,400 AF. The pumping rate decreased from 0.6 to 0.4 to reflect the decreasing demand on groundwater supplies over the past five years, although the volume available did not actually decrease.
EXHIBIT 1
7 Water Supply Reliability and Drought Risk Assessment 2025 UWMP 7-5
Table 7-4: Basis of Water Year Data for COS Groundwater Wells (DWR Table 7-1 Retail) Year Type
Base Year
If not using a
calendar year, type
in the last year of
the fiscal, water
year, or range of
years, for example,
water year 2024-
2025, use 2025
Available Supplies if
Year Type Repeats
Check the box if quantification of available supplies is not compatible with this table and is provided
elsewhere in the UWMP.
Location: [insert location from UWMP]
Quantification of available supplies is provided in this table as either volume only, percent only, or both.
Volume Available % of Average Supply
15,400
Average Year 2020 15,400 100%
Single-Dry Year 2019 15,400 100%
Consecutive Dry Years 1st Year 2015 15,400 100%
Consecutive Dry Years 2nd Year 2016 15,400 100%
Consecutive Dry Years 3rd Year 2017 15,400 100%
Consecutive Dry Years 4th Year 2018 15,400 100%
Consecutive Dry Years 5th Year 2019 15,400 100%
7.2.5 Normal Year Supply and Demand Comparison
Normal year supply projections from this chapter and projected demands from Chapter 4 are compared in Table 7-5 below. The average projected surplus for a normal supply year over the next 25 years is 47,700 AF.
EXHIBIT 1
7 Water Supply Reliability and Drought Risk Assessment 2025 UWMP 7-6
Table 7-5: Normal Year Supply and Use Comparison (DWR Table 7-2 Retail) Submittal Table 7-2 Retail: Normal Year Supply and Use Comparison Water Code Section 10635 (a)
2030 2035 2040 2045 2050
(AF) (AF) (AF) (AF) (AF)
Supply totals
(autofill from Submittal
Table 6-9 R)
76,250 77,450 78,450 79,450 80,600
SEWD 20,000 20,000 20,000 20,000 20,000
WID 8,850 9,850 10,850 11,850 13,000
San Joaquin River 24,800 25,000 25,000 25,000 25,000
COSMUD Wells 15,400 15,400 15,400 15,400 15,400
Demand Totals
(autofill from Submittal
Table 4-2 R)
29,768 30,233 30,704 31,183 31,670
Surplus/(shortfall) 46,482 47,217 47,746 48,267 48,930
7.2.6 Single Dry Year Supply and Demand Comparison
Single Dry year supply projections from this chapter and projected demands from Chapter 4 are compared in Table 7-6 below. The average projected surplus for a single dry year over the next 25 years is 34,100 AF.
EXHIBIT 1
7 Water Supply Reliability and Drought Risk Assessment 2025 UWMP 7-7
Table 7-6: Single Dry Year Supply and Use Comparison (DWR Table 7-3 Retail) Submittal Table 7-3 Retail: Single Dry Year Supply and Use Comparison Water Code Section 10635(a)
2030 2035 2040 2045 2050 (Opt)
(AF) (AF) (AF) (AF) (AF)
Supply totals 64,830 64,830 64,830 64,830 64,830
SEWD 6,600 6,600 6,600 6,600 6,600
WID 4,080 4,080 4,080 4,080 4,080
San Joaquin River 18,150 18,150 18,150 18,150 18,150
COSMUD Wells 15,400 15,400 15,400 15,400 15,400
Demand Totals 29,768 30,233 30,704 31,183 31,670
Surplus/(shortfall) 35,062 34,597 34,126 33,647 33,160
7.2.7 Multiple Dry Years Supply and Demand Comparison
Multiple Dry years supply projections from this chapter and projected demands from Chapter 4 are compared in Table 7-7 below. The average projected surplus for multiple dry years over the next 25 years is 38,000 AF.
EXHIBIT 1
7 Water Supply Reliability and Drought Risk Assessment 2025 UWMP 7-8
Table 7-7: Multiple Dry Years Supply and Use Comparison (DWR Table 7-4 Retail) Submittal Table 7-4 Retail: Multiple Dry Years Supply and Use Comparison Water Code Section 10635(a)
2030 2035 2040 2045 2050 (Opt)
(AF) (AF) (AF) (AF) (AF)
First year
Supply Totals 58,763 58,763 58,763 58,763 58,763
SEWD 20,983 20,983 20,983 20,983 20,983
WID 4,080 4,080 4,080 4,080 4,080
San Joaquin River 18,300 18,300 18,300 18,300 18,300
Groundwater Wells 15,400 15,400 15,400 15,400 15,400
Demand Totals 30,468 31,293 31,293 31,183 31,670
Surplus/(shortfall) 28,995 28,530 28,059 27,580 27,093
Second year
Supply Totals 65,042 65,042 65,042 65,042 65,042
SEWD 22,649 22,649 22,649 22,649 22,649
WID 7,993 7,993 7,993 7,993 7,993
San Joaquin River 19,000 19,000 19,000 19,000 19,000
Groundwater Wells 15,400 15,400 15,400 15,400 15,400
Demand Totals 30,468 31,293 31,293 31,183 31,670
Surplus/(shortfall) 34,574 33,749 33,749 33,859 33,372
Third year
Supply Totals 64,938 64,938 64,938 64,938 64,938
SEWD 25,778 25,778 25,778 25,778 25,778
WID 4,760 4,760 4,760 4,760 4,760
San Joaquin River 19,000 19,000 19,000 19,000 19,000
Groundwater Wells 15,400 15,400 15,400 15,400 15,400
EXHIBIT 1
7 Water Supply Reliability and Drought Risk Assessment 2025 UWMP 7-9
Table 7-8: Multiple Dry Years Supply and Use Comparison (DWR Table 7-4 Retail) continued Demand Totals 31,168 32,353 32,353 31,183 31,670
Surplus/(shortfall) 33,770 32,585 32,585 33,755 33,268
Fourth year
Supply Totals 66,592 66,592 66,592 66,592 66,592
SEWD 27,564 27,564 27,564 27,564 27,564
WID 4,628 4,628 4,628 4,628 4,628
San Joaquin River 19,000 19,000 19,000 19,000 19,000
Groundwater Wells 15,400 15,400 15,400 15,400 15,400
Demand Totals 31,868 33,413 33,413 31,183 31,670
Surplus/(shortfall) 34,724 33,179 33,179 35,409 34,922
Fifth year
Supply Totals 72,875 72,875 72,875 72,875 72,875
SEWD 28,562 28,562 28,562 28,562 28,562
WID 9,913 9,913 9,913 9,913 9,913
San Joaquin River 19,000 19,000 19,000 19,000 19,000
Groundwater Wells 15,400 15,400 15,400 15,400 15,400
Demand Totals 32,568 34,473 34,473 31,183 31,670
Surplus/(shortfall) 40,307 38,402 38,402 41,692 41,205
7.3 Drought Risk Assessment (DRA)
The drought risk assessment evaluates COSMUD’s ability to meet projected water demands during a severe drought lasting five consecutive water years. This assessment relies on historic five-year hydrologic drought within COSMUD’s water supply portfolio. Drought risk is assessed by comparing projected water supplies under constrained conditions against projected water demands, and the analysis is intended to identify potential supply shortfalls and inform long-term planning and drought preparedness actions. Reduced surface water availability, groundwater pumping constraints, and environmental or regulatory limitations are key factors influencing drought vulnerability. For this UWMP, the DRA considers five consecutive dry years from 2026 through 2030.
EXHIBIT 1
7 Water Supply Reliability and Drought Risk Assessment 2025 UWMP 7-10
7.4 DRA Water Source Reliability
Table 7-8 below provides the anticipated water supply over the next five years in a hypothetical drought scenario. Total supplies values were calculated by summing the consecutive five-year drought values provided for each water source in Tables 7-1 through 7-4, which establish the lowest amount of water available based on historical data for five consecutive years. Total water use for the year 2030 was taken from the projected water use for 2030 found in Table 4-3, and an assumed 1.5 percent reduction in demand was assumed for years 2026 through 2029. The total water use projected for 2026 is identical to the average water demand between 2020 and 2025, which is 32,325 AFY.
Table 7-9: Five-Year Drought Risk Assessment (DWR Table 7-5 Retail) Submittal Table 7-5 Retail: Five-Year Drought Risk Assessment Water Code Section 10635(b)(3)
2026 Total
Total Water Use (AF) 32,352
Total Supplies (AF) 58,763
Surplus/Shortfall w/o WSCP Action 26,411
2027 Total
Total Water Use (AF) 32,845
Total Supplies (AF) 65,042
Surplus/Shortfall w/o WSCP Action 32,197
2028 Total
Total Water Use (AF) 33,345
Total Supplies (AF) 64,938
Surplus/Shortfall w/o WSCP Action 31,593
2029 Total
Total Water Use (AF) 33,853
Total Supplies (AF) 65,692
Surplus/Shortfall w/o WSCP Action 31,839
2030 Total
Total Water Use (AF) 34,368
Total Supplies (AF) 75,175
Surplus/Shortfall w/o WSCP Action 40,807
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7 Water Supply Reliability and Drought Risk Assessment 2025 UWMP 7-11
7.5 Summary
Based on the analyses presented in this chapter and supporting UWMP tables, the City has sufficient water supplies and system capacity to meet projected demands over the planning horizon under normal, single dry, and multiple dry year conditions, consistent with the conclusions of the 2021 Water Master Plan and prior UWMP cycles. In a five-year drought scenario between 2026 and 2030, the average surplus of water supplies is 32,570 AF.
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CHAPTER 8 –WATER SHORTAGE CONTINGENCY PLAN
8 Water Shortage Contingency Plan
Water shortage contingency planning is a proactive planning process intended to prepare for and respond to potential water supply shortages. Effective planning and preparedness enable water suppliers to maintain reliable service and minimize impacts to customers during periods of supply interruption. Water shortages may result from a variety of factors, including population growth, climate change, drought conditions, regulatory constraints, and natural or human-caused emergencies. A water shortage occurs when available water supplies are insufficient to meet normal customer demands at a given time.
The Water Shortage Contingency Plan (WSCP) outlines the establishes the procedures, authorities, and response actions the City will use to prepare for and respond to water supply shortages. The WSCP anticipates potential supply constraints and provides pre-established measures to manage and mitigate the effects of shortages, including drought and emergency events, which may occur at any time. Even where the likelihood of shortages is low, the WSCP serves as an essential component of drought preparedness and overall water supply reliability.
8.1 City Water Shortage Contingency Plan
The City’s WSCP is included in Attachment D. The City’s 2025 WSCP establishes a comprehensive framework for managing potential water supply shortages in the municipal water system. Its primary goals are to minimize service disruptions, protect public health and safety, and ensure regulatory compliance during droughts, infrastructure issues, regulatory constraints, or emergencies. The WSCP is closely linked to the City’s 2025 UWMP but is designed to be a flexible, stand-alone document that can be updated independently. Legal authority for the plan is provided by Stockton Municipal Code Chapters
13.28 (Water Conservation) and 13.32 (Water Shortage Emergencies), which define enforceable conservation requirements, shortage stages, and response actions.
The plan describes the City’s diversified, conjunctive-use water supply portfolio; procedures for completing the Annual Water Supply and Demand Assessment and submitting the Annual Water Shortage Assessment Report to the California Department of Water Resources; and six standard water shortage stages with corresponding supply augmentation, demand-reduction, operational, communication, compliance, and enforcement actions. The WSCP also documents communication protocols for foreseeable and unforeseeable events, financial considerations, monitoring and reporting procedures, and processes for plan refinement, adoption, and public availability to ensure reliable water service and protection of public health and safety during shortage conditions.
8.2 Seismic Risk Assessment and Mitigation Plan
California Water Code §10632.5(a) requires UWMPs to include a seismic risk assessment and mitigation plan for existing water system facilities and allows a supplier to meet this requirement by relying on a EXHIBIT 1
8 Water Shortage Contingency Plan 2025 UWMP
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Local Hazard Mitigation Plan (LHMP) if it includes a seismic risk assessment. The City participated in development of the 2023 San Joaquin County LHMP, which was adopted April 11, 2023 and later found approvable by FEMA in April 2023; however, because the 2023 LHMP does not provide the earthquake/seismic assessment needed for this UWMP, it is not used to satisfy the UWMP seismic assessment requirement.
Separately, in March 2025 the City completed an AWIA Risk and Resilience Assessment (RRA) evaluating natural hazard risks (including earthquakes) to critical potable water assets (e.g., sources, wells, treatment/chlorination, storage, pump stations, distribution, and supporting systems) to identify critical components and inform resilience improvements; RRAs must be reviewed and re-certified every five years.
The RRA is maintained as a confidential document.
8.3 Water Shortage Contingency Plan Adoption, Submittal, and Availability
This WSCP update has been prepared in tandem with the City’s 2025 UWMP. The WSCP (including subsequent updates) shall be adopted in accordance with standard City procedures, which include requirements for public participation (public hearing), and approval by the City Council. Upon adoption, the WSCP will be submitted to DWR within 30 days. The adopted WSCP will be made publicly available on the City’s website through the Municipal Utilities water planning pages and the City’s public document repository, where adopted water planning documents are posted for public access.
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CHAPTER 9 – DEMAND MANAGEMENT MEASURES
9 Demand Management Measures
COSMUD implements demand management measures (DMM) to support efficient water use and maintain water service reliability as demand grows, and supply conditions change due to climate variability and other factors. This chapter summarizes the City’s conservation program and documents the status of the required demand management measures, including planned continuation.
9.1 Water Conservation Program Overview
COSMUD maintains an ongoing water conservation program applicable to all customer sectors. The following sections summarize the nature and extent of implementation of each required DMM including actions implemented during 2016–2020 and planned continuation.
9.2 Water Waste Prevention Ordinances
9.2.1 DMM Description
COSMUD implements enforceable water conservation requirements through Stockton Municipal Code (SMC) provisions addressing water waste. SMC Chapter 13.28 is dedicated to water conservation and includes prohibitions on water waste (e.g., restrictions on hosing hardscapes, washing vehicles without a shut‑off nozzle, and irrigating in a manner that causes runoff).
9.2.2 Implementation over the Past Five Years
Water waste prohibitions remain in effect as a baseline demand management measure and support implementation of WSCP-related requirements and response actions. The City’s WSCP legal authority framework references SMC Chapter 13.28 and SMC Chapter 13.32 as supporting authorities for shortage response actions.
9.2.3 Plans for Continued Implementation / Planned Activities The City will continue administering water waste prohibitions and will update implementing code provisions as needed to maintain consistency with WSCP requirements and applicable state guidance.
9.3 Metering
9.3.1 DMM Description
COSMUD’s service area is fully metered and all connections are billed based on metered consumption.
Customer classes include single‑family residential, multi‑family residential, non‑residential, and irrigation accounts, and metering is the basis for demand accounting and billing.
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9.3.2 Implementation over the Past Five Years
Metering is maintained for all accounts and is integrated into routine customer billing and demand tracking. This measure is fully implemented as the standard approach for measuring and managing delivered water.
9.3.3 Plans for Continued Implementation / Planned Activities COSMUD will continue installing and maintaining meters for new services and ongoing system operation. COSMUD is also actively pursuing Advanced Metering Infrastructure (AMI), as discussed in Chapter 6, to improve metering efficiency and customer access to usage data; the effort is ongoing and, to date, no discernable demand reductions have been observed.
9.4 Conservation Pricing
9.4.1 DMM Description
COSMUD applies conservation pricing through volumetric billing based on metered consumption using the City’s adopted water rate schedule. Rate structures include an increasing block structure for single‑family residential customers and seasonal rate structures for multi‑family, non‑residential, and irrigation accounts, with higher summer rates.
9.4.2 Implementation over the Past Five Years
The City routinely reviews and updates its water rates. The City’s rate structure has included conservation pricing and, during prior shortage response conditions, drought recovery charges correlated to customer class and shortage response stages to encourage compliance with demand reduction actions and support financial stability under reduced sales conditions.
9.4.3 Plans for Continued Implementation / Planned Activities COSMUD will continue using conservation‑oriented rate design and periodic rate review to support efficient water use and maintain fiscal stability, consistent with WSCP implementation needs and long‑term water efficiency objectives.
9.5 Public Education and Outreach
9.5.1 DMM Description
COSMUD conducts public education and outreach to promote water conservation and inform customers regarding efficient water use. Outreach components include a water conservation website, education activities, WaterSense partnership participation, and distribution of conservation information.
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The Stockton Area Water Suppliers (SAWS) Water Education Program provides grade‑specific water education and conservation outreach to elementary students in the Stockton area through in‑class presentations, youth‑oriented events, and supplemental virtual resources. The program serves schools in four districts and delivers curriculum aligned with Next Generation Science Standards (NGSS) covering water science, water supply systems, drought, conservation, and California water issues. Presentations incorporate hands‑on activities and visual demonstrations, with supporting materials provided to students and teachers. The full SAWS Water Education Program Annual Report is included in Attachment L.
The Classroom Aquarium Education Program (CAEP) provides hands‑on environmental education by allowing students to raise Chinook salmon in classroom aquariums. The program teaches students about aquatic ecosystems, salmon life cycles, and the importance of protecting natural resources.
Instruction aligns with the California Science Education Standards and emphasizes environmental stewardship through direct observation and experiential learning. More information on the CAEP is included in Attachment M.
9.5.2 Implementation over the Past Five Years
Public education and outreach has been supported through annual budgeted program funding. Prior UWMP documentation reports an average annual outreach budget for 2016–2020 and describes outreach delivery through community venues and events, including distribution of literature and hands‑on engagement activities. As a USEPA WaterSense Partner, the City uses WaterSense materials and promotes water‑efficient products and water awareness.
Over the past five years, SAWS has consistently implemented the Water Education Program using a combination of in‑person classroom presentations and virtual educational tools. The program has utilized digital resources, including online instructional materials and videos, to supplement classroom instruction and expand access to program content. Outreach has reached thousands of students annually through classroom presentations and youth‑oriented community events, with continued demand across participating school districts.
CAEP has been implemented in Stockton-area classrooms with support from local sponsors. COSMUD became a sponsor in the 2022 salmon season, supporting participation by 18 local K–12 schools to date.
Participating teachers receive required training and permits, classroom aquariums are installed prior to egg delivery, and approximately 35 Chinook salmon eggs are provided per classroom from the Mokelumne River Hatchery. Students raise salmon for approximately eight weeks before participating in a supervised release into a local stream or river.
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9.5.3 Plans for Continued Implementation/Planed Activities COSMUD will continue public education and outreach activities, including WaterSense-based messaging and community engagement, to support ongoing conservation awareness and future water-use objectives.
SAWS will continue implementing the Water Education Program through ongoing in-class presentations, virtual educational tools, and youth-oriented community events. Planned activities include maintaining grade-appropriate, standards-aligned curricula; refining and updating instructional materials as needed; continuing collaboration with school districts and educators; and sustaining staffing and coordination to support long-term water awareness and conservation education.
CAEP will continue to be implemented through ongoing partnerships with schools, sponsors, and the California Department of Fish and Wildlife. Future activities will continue to include teacher training, classroom aquarium setup, salmon egg delivery, in‑class observation, and student field trips for salmon release. The program will remain aligned with state science education standards and will continue to promote student awareness of aquatic ecosystems and water resource protection.
9.6 Programs to Assess and Manage Distribution System Real Loss
9.6.1 DMM Description
COSMUD assesses distribution system losses using AWWA Water Audits and Loss Control Program methodology and reports distribution system loss consistent with UWMP reporting requirements.
The COSMUD distribution system includes approximately 584 miles of distribution pipelines and transmission mains as described in prior UWMP documentation.
9.6.2 Implementation over the Past Five Years
COSMUD continues routine loss accounting and tracking consistent with AWWA audit-based practices and UWMP reporting. The City’s UWMP framework includes prior five‑year water loss audit reporting and recognizes emerging requirements associated with the State Water Board water loss performance standard.
9.6.3 Plans for Continued Implementation / Planned Activities COSMUD will continue using audit-based loss tracking and operational practices intended to identify and reduce real losses. Narrative reporting will be maintained consistent with Chapter 4 water loss reporting and the 2025 Guidebook’s expectation to describe current and planned leak detection/repair efforts and planning considerations for performance standards.
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9.7 Water Conservation Program Coordination and Staffing Support
9.7.1 DMM Description
Water conservation program coordination is conducted by the City’s Water Resources Program Manager. The Program Manager administers the DMMs, estimates conservation savings achieved, and establishes an annual program budget based on available funding and resources. Documented duties include tracking program accomplishments and annual reporting, developing conservation goals, coordinating surveys and monthly O&M reporting, tracking production/demand and submitting monthly monitoring reports, and preparing annual USEPA reporting.
9.7.2 Implementation over the Past Five Years
This DMM is ongoing and supports consistent implementation and administration of COSMUD’s demand management program across customer sectors and internal City functions.
9.7.3 Plans for Continued Implementation / Planned Activities COSMUD will continue conservation program coordination and staffing support as an enabling function for conservation program delivery, reporting, and prioritization, consistent with 2025 Guidebook expectations for documenting coordination activities and staffing support.
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CHAPTER 10 – PLAN ADOPTION, SUBMITTAL, AND
IMPLEMENTATION
10 Plan Adoption, Submittal, and Implementation
This chapter covers notification, public hearing, adoption, and submission of the COSMUD 2025 UWMP and WSCP. It also discusses plan implementation and the amendment process for both documents.
10.1 Notice of Plan Preparation
CWC §10642 requires encouragement of public participation and a public hearing prior to the adoption of the 2025 UWMP and WSCP. In order to reach the “diverse social, cultural, and economic elements of the population” within COSMUD’s service area, a public hearing will be held on May 12, 2026. The public hearing will include a presentation to the public. This session will be held for review and comment of the draft UWMP and WSCP before adoption by COSMUD.
10.1.1 Notices to Cities, Counties, and the Public
The following notifications were sent to all cities and counties within which COSMUD provides water:
• 60-Day Notification Letters: Letters were sent at least 60-days prior to the public hearing to provide notification that COSMUD was preparing its 2025 UWMP. • Notice of Public Hearing: Letters will be sent out at least 2 weeks prior to the public hearing to provide notice of the planned time and location of the public hearing. These letters are also to inform that a Public Draft of COSMUD’s 2025 UWMP and WSCP was available for public review on COSMUD’s website.
Both notification letters are included in Attachment N.
Table 10- 1. Notifications to Cities and Counties.
County Name 60Day Notice Notice of Public
Hearing
San Joaquin
County Public
Works
Yes
Eastern San
Joaquin
Groundwater
Authority
Yes
10.2 Public Hearing and Adoption - To Be Developed in Future Submittal
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10 Plan Adoption, Submittal, and Implementation 2025 UWMP 10-2
10.3 Plan Submittal - To Be Developed in Future Submittal
10.3.1 Submitting a UWMP and Water Shortage Contingency Plan to DWR - To Be Developed in Future Submittal
10.3.2 Electronic Data Submittal - To Be Developed in Future Submittal
10.3.3Submitting a UWMP, Including WSCP, to the California State Library - To Be Developed in Future Submittal
10.3.4Submitting a UWMP to Cities and counties - To Be Developed in Future Submittal
10.4 Public Availability - To Be Developed in Future Submittal
10.5 Notification to Public Utilities Commission - To Be Developed in Future Submittal
10.6 Plan Implementation - To Be Developed in Future Submittal
10.7 Amending an Adopted Urban Water Management Plan - To Be Developed in Future Submittal
10.7.1 Amending a UWMP or WSCP - To Be Developed in Future Submittal
10.7.2 Submitting Revised Water Shortage Contingency Plan - To Be Developed in Future Submittal
10.8 California Department of Water Resources Review of Submitted Plans - To Be Developed in Future Submittal
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ATTACHMENT A: UWMP CHECKLIST ARRANGED BY SUBJECT
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Attachment A UWMP Checklist Arranged by Subject
Retail (x = required) Wholesale (x = required) Order 2025 Guidebook Location Water Code Section Summary as Applies to UWMP Subject Relevant Submittal Table 2025 UWMP Location x x 1 Chapter 1 10615 A plan shall describe and evaluate sources of supply, reasonable and practical efficient uses, reclamation and demand management activities. Introduction and overview n/a Ch. 1, Executive Summary x x 1 Chapter 1 10630.5
Each plan shall include a simple description of the Supplier’s plan including water availability, future requirements, a strategy for meeting needs, and other pertinent information. Additionally, a Supplier may also choose to include a simple description at the beginning of each chapter.
Plan preparation n/a Ch. 1.4, Executive Summary
x x 2.1 Section 2.1 10620(b) Every person that becomes a Supplier shall adopt UWMP within one year after it has become a Supplier. Plan preparation n/a Ch.2.1 x n/a 2.5 Section 2.5 10644 Supplier shall report the Public Water Systems number, volume of delivered water, and number of connections that are included in this UWMP. Plan preparation 2-1 Ch.2.1x x 2.5 Section 2.5 10644 Supplier shall report if this UWMP is an individual UWMP and whether the Supplier belongs to a regional UWMP or regional alliance. Plan preparation 2-2 Ch. 2.2 x x 2.5 Section 2.5 10644 Supplier shall report whether the data is in fiscal or calendar years and the units of measure used for reporting water volumes. Plan preparation 2-3 Ch. 2.4x x 2.4 Section 2.4 10642 Provide supporting documentation that the Supplier has encouraged active involvement of diverse social, cultural, and economic elements of the population within the service area prior to and during the preparation of the plan and contingency plan. Plan preparation n/a x x 2.4 Section 2.4.2 10620(d)(3) Coordinate the preparation of its plan with other appropriate agencies in the area, including other Suppliers that share a common source, water management agencies, and relevant public agencies, to the extent practicable. Plan preparation n/ax n/a 2.4 Section 2.4.1 10631(h) Retail Suppliers will include documentation that they have provided their Wholesale Supplier(s)—if any—with water use projections from that source. Plan preparation 2-4 R Ch. 2.5 n/a x 2.4 Section 2.4.1 10631(h) Wholesale Suppliers will provide their Suppliers with identification and quantification of the existing and planned sources of water available from the Wholesale Supplier to the Supplier during various water year types. Plan preparation 2-4 W x x 3 Chapter 3.0 10631(a) Describe the Supplier service area. System description n/a Ch. 3.2 x x 3.3 Section 3.3 10631(a) Describe the climate of the Supplier’s service area. System description n/a Ch. 3.3x x 3.4 Section 3.4.1 10631(a) Provide the current and projected service area populations for 2030, 2035, 2040, 2045 and optionally 2050. System description 3-1 Ch.3.4.1 x x 3.4 Section 3.4.2 10631(a) Describe other social, economic, and demographic factors affecting the Supplier’s water management planning. System description n/a Ch.3.4.2 x x 3.5 Section 3.5 10631(a) Describe the land uses within the service area… include the current and projected land uses within the existing or anticipated service area affecting the Supplier’s water management planning. Describe the land uses within the service area. System description and baselines n/a Ch.3.5 x Optional 4.2 Sections 4.2.3 and 4.2.4 10631(d)(1) Quantify past, current, and projected water use, identifying the uses among water use sectors. System water use 4-1 and 4-2 Ch 4.2x Optional 4.3 Section 4.3.1 10631(d)(3)(A) Report the distribution system water loss for each of the five years preceding the plan update. System water use 4-5 Ch 4.4 x n/a 4.3 Section 4.3.2 10631(d)(3)(C) Retail Suppliers shall provide data to show the distribution loss standards were met. System water use 4-6 Ch 4.4x n/a 4.2 Section 4.2.5.4 10631.1(a) Include projected water use needed for lower income housing projected in the service area of the Supplier. System water use 4-3 Ch 4.2x n/a 4.2 Section 4.2.5.3 10631(d)(4)(A) In projected water use, include estimates of water savings from adopted codes, plans, and other policies or laws. System water use 4-3 Ch 4.3x n/a 4.2 Section 4.2.5.3 10631(d)(4)(B) Provide citations of codes, standards, ordinances, or plans used to make water use projections. System water use 4-3 Ch 4.2x n/a 4.2 Section 4.2.5.3 10631(d)(4)(B)(ii) To the extent that a Supplier reports the information described in subparagraph (A), an urban water Supplier shall… Indicate the extent that the water use projections consider savings from codes, standards, ordinances, or transportation and land use plans. Water use projections that do not account for these water savings shall be noted of that fact.
System water use 4-3 Ch 4.3
x x 4.2 Section 4.2.5.6 10635(b) Demands under climate change considerations must be included as part of the drought risk assessment. System water use n/a Ch 4.6 n/a x 5.1 Section 5.1 10608.36 Wholesale Suppliers shall include an assessment of present and proposed future measures, programs, and policies to help their Retail Suppliers achieve targeted water use reductions. Baselines and targets n/a x n/a 5.2 Section 5.2 10608.4
Retail Suppliers shall report on their compliance in meeting their water use targets. Reporting requirements will vary depending on whether the Supplier:- Was considered an urban retail water supplier in 2020,- Met its 2020 target in 2020, or- Was part of a merger or consolidation since 2020.Chapter 5 Subsections 5.2.1, 5.2.2, and 5.2.3 address each of these situations.
Baselines and targets 5-1 Ch 5
x x 6.1 Section 6.1 10631(b)(2) When multiple sources of water supply are identified, describe the management of each supply in relationship to other identified supplies. System supplies n/a 6.3, 6.4, 6.5 x x 6.1 Sections 6.1 and 6.2 10631(b)(1) Provide a discussion of anticipated supply availability under a normal, single dry year, and a drought lasting five years, as well as more frequent and severe periods of drought, including changes in supply due to climate change. System supplies n/a Ch 7 x x 6.2 Section 6.2.2 10631(b)(4)(C)
Indicate whether groundwater is an existing or planned source of water available to the Supplier. If groundwater is identified as an existing or planned source of water… (include) a detailed description and analysis of the location, amount and sufficiency of groundwater pumped by the Supplier for the past five years.
Water supplies and recycled water 6-1 Ch 6
x x 6.2 Section 6.2.2 10631(b)(4)(A) Indicate whether a groundwater sustainability plan or groundwater management plan has been adopted by the Supplier or if there is any other specific authorization for groundwater management. Include a copy of the plan or authorization. System supplies n/a 6.5 x x 6.2 Section 6.2.2 10631(b)(4)(B) Describe the groundwater basin. System supplies n/a 6.4 1 EXHIBIT
1 Attachment A UWMP Checklist Arranged by Subject
x x 6.2 Section 6.2.2 10631(b)(4)(B) Indicate if the basin has been adjudicated and include a copy of the court order or decree and a description of the amount of water the Supplier has the legal right to pump. System supplies n/ax x 6.2 Section 6.2.2 10631(b)(4)(B) For unadjudicated basins… (include) information as to whether DWR has identified the basin as a high- or medium-priority basin in the most current official departmental bulletin… Water supplies and recycled water n/ax x 6.2 Section 6.2.2 10631(b)(4)(B) For unadjudicated basins… describe efforts by the Supplier to coordinate with sustainability or groundwater agencies to achieve sustainable groundwater conditions. Water supplies and recycled water n/ax x 6.2 Section 6.2.2. 10631(b)(4)(C) If groundwater is identified as an existing or planned source of water… (include) a detailed description and analysis of the location, amount and sufficiency of groundwater pumped by the Supplier for the past five years. System supplies n/a 6.4x x 6.2 Section 6.2.2 10631(b)(4)(D) Provide a detailed description and analysis of the amount and location of groundwater that is projected to be pumped. System supplies 6-9 6.8x x 6.1 Section 6.1 10631(b) Identify and quantify the existing and planned sources of water available for 2025, 2030, 2035, 2040, 2045 and optionally 2050. System supplies 6-8 and 6-9 6.8x x 6.2 Section 6.2.7 10631(c) Describe the opportunities for exchanges or transfers of water on a short-term or long-term basis. System supplies n/a x n/a 6.2 Section 6.2.5 10633(a) Describe the wastewater collection and treatment systems in the Supplier’s service area with quantified amount of collection and treatment and the disposal methods. System supplies (recycled water) 6-2 6.6x x 6.2 Section 6.2.5 10633(b) Describe the quantity of treated wastewater that meets recycled water standards, is being discharged, and is otherwise available for use in a recycled water project. System supplies (recycled water) 6-3 6.6x x 6.2 Section 6.2.5 10633(c) Describe the recycled water currently being used in the Supplier's service area. System supplies (recycled water) 6-4 6.6.2x x 6.2 Section 6.2.5 10633(d) Describe and quantify the potential uses of recycled water and provide a determination of the technical and economic feasibility of those uses.
System supplies (recycled water) 6-4
x x 6.2 Section 6.2.5 10633(e) Describe the projected use of recycled water within the Supplier's service area at the end of 5, 10, 15, and 20 years, and describe the actual use of recycled water in comparison to uses previously projected. System supplies (recycled water) 6-4 and 6-5 6.6.2 x x 6.2 Section 6.2.5 10633(f) Describe the actions that may be taken to encourage the use of recycled water and the projected results of these actions in terms of acre- feet of recycled water used per year. System supplies (recycled water) 6-6 x x 6.2 Section 6.2.5 10633(g) Provide a plan for optimizing the use of recycled water in the Supplier's service area. System supplies (recycled water) n/a x x 6.2 Section 6.2.6 10631(g) Describe desalinated water project opportunities for long-term supply. System supplies 6-7x x 6.2 Section 6.2.10 10631(f) Describe the expected future water supply projects and programs that may be undertaken by the water Supplier to address water supply reliability in average, single-dry, and for a period of drought lasting five consecutive water years. System supplies 6-7 6.7 x x 6.3 Section 6.3 and Appendix O 10631.2(a) The UWMP must include energy information, as stated in the code, that a Supplier can readily obtain. System suppliers, energy intensity O-1A, O-1B, O-1C, and O-2 6.9 x 7.1 Section 7.1 10634 Provide information on the quality of existing sources of water available to the Supplier and the manner in which water quality affects water management strategies and supply reliability. Water supply reliability assessment n/a x x 7.2 Section 7.2 10635(a) Service Reliability Assessment: Assess the water supply reliability during normal, dry, and a drought lasting five consecutive water years by comparing the total water supply sources available to the Supplier with the total projected water use over the next 20 years. Water supply reliability assessment 7-2, 7-3, and 7-4 Ch 7 x x 7.2 Section 7.2.3 10620(f) Describe water management tools and options to maximize resources and minimize the need to import water from other regions. Water supply reliability assessment n/a x x 7.3 Section 7.3 10635(b) Provide a drought risk assessment as part of information considered in developing the demand management measures and water supply projects. Water supply reliability assessment n/a Ch 7 x x 7.3 Section 7.3 10635(b)(1) Include a description of the data, methodology, and basis for one or more supply shortage conditions that are necessary to conduct a drought risk assessment for a drought period that lasts five consecutive years. Water supply reliability assessment n/a Ch 7 x x 7.3 Section 7.3 10635(b)(2) Include a determination of the reliability of each source of supply under a variety of water shortage conditions. Water supply reliability assessment n/a Ch 7 x x 7.3 Section 7.3 10635(b)(3) Include a comparison of the total water supply sources available to the Supplier with the total projected water use for the drought period. Water supply reliability assessment 7-5 7.2.7 x x 7.3 Section 7.3 10635(b)(4) Include considerations of the historical drought hydrology, plausible changes on projected supplies and demands under climate change conditions, anticipated regulatory changes, and other locally applicable criteria. Water supply reliability assessment n/a Ch 7 x x 8 Chapter 8 10632(a) Provide a water shortage contingency plan (WSCP) with specified elements below. Water shortage contingency planning n/a Ch. 8 x x 8 Chapter 8 10632(a)(1) Provide an analysis of water supply reliability (from Guidebook Chapter 7) in the WSCP. Water shortage contingency planning n/a Section 1 of WSCP x x 8.2 Section 8.2 10632(a)(2)(A) Provide the written decision-making process and other methods that the Supplier will use each year to determine its water reliability. Water shortage contingency planning n/a Section 2.1 of WSCP x x 8.2 Section 8.2 10632(a)(2)(B) Provide data and methodology to evaluate the Supplier’s water reliability for the current year and one dry year pursuant to factors in the code. Water shortage contingency planning n/a Section 2.2 and 2.3 of WSCP x x 8.3 Section 8.3 10632(a)(3)(A)
Define six standard water shortage levels of 10%, 20%, 30%, 40%, 50% shortage, and greater than 50% shortage. These levels shall be based on supply conditions, including percent reductions in supply, changes in groundwater levels, changes in surface elevation, or other conditions. The shortage levels shall also apply to a catastrophic interruption of supply.
Water shortage contingency planning n/a Section 3 of WSCP x x 8.3 Section 8.3 10632(a)(3)(B) Suppliers with an existing WSCP that uses different water shortage levels must cross reference their categories with the six standard categories. Water shortage contingency planning 8-1 N/A x x 8.4 Section 8.4 10632(a)(4)(A) Suppliers with WSCPs that align with the defined shortage levels must specify locally appropriate supply augmentation actions. Water shortage contingency planning 8-2 Section 4.1 of WSCP x x 8.4 Section 8.4 10632(a)(4)(B) Specify locally appropriate demand reduction actions to adequately respond to shortages. Water shortage contingency planning 8-3 Section 4.2 of WSCP 2 EXHIBIT
1 Attachment A UWMP Checklist Arranged by Subject
x x 8.4 Section 8.4 10632(a)(4)(C) Specify locally appropriate operational changes. Water shortage contingency planning 8-2 Section 4.3 of WSCP x x 8.4 Section 8.4 10632(a)(4)(D) Specify additional mandatory prohibitions against specific water use practices that are in addition to State-mandated prohibitions are appropriate to local conditions. Water shortage contingency planning Table 8-3 Section 4.4 of WSCP x x 8.4 Section 8.4 10632(a)(4)(E) Estimate the extent to which the gap between supplies and demand will be reduced by implementation of the action. Water shortage contingency planning 8-2 and 8-3 Sections 4.2 of WSCP x x 8.4 Section 8.4.6 10632.5 The UWMP shall include a seismic risk assessment and mitigation plan. Water shortage contingency plan n/a Section 4.6 of WSCP x x 8.5 Section 8.5 10632(a)(5)(A) Suppliers must describe that they will inform customers, the public and others regarding any current or predicted water shortages. Water shortage contingency planning n/a Section 5 of WSCP x x 8.5 Section 8.5 10632(a)(5)(B), 10632(a)(5)(C) Suppliers must describe that they will inform customers, the public and others regarding any shortage response actions triggered or anticipated to be triggered and other relevant communications. Water shortage contingency planning n/a Section 5 of WSCP x n/a 8.6 Section 8.6 10632(a)(6) Retail Supplier must describe how it will ensure compliance with and enforce provisions of the WSCP. Water shortage contingency planning n/a Section 6 of WSCPx x 8.7 Section 8.7 10632(a)(7)(A) Describe the legal authority that empowers the Supplier to enforce shortage response actions. Water shortage contingency planning n/a Section 7.1 of WSCP x x 8.7 Section 8.7 10632(a)(7)(B) Provide a statement that the Supplier will declare a water shortage emergency per Water Code Chapter 3. Water Shortage Emergencies . Water shortage contingency planning n/a Section 7.2 of WSCPx x 8.7 Section 8.7 10632(a)(7)(C) Provide a statement that the Supplier will coordinate with any city or county within which it provides water for the possible proclamation of a local emergency. Water shortage contingency planning n/a Section 7.3 of WSCP x x 8.8 Section 8.8 10632(a)(8)(A) Describe the potential revenue reductions and expense increases associated with activated shortage response actions. Water shortage contingency planning n/a Section 8.1 of WSCP x x 8.8 Section 8.8 10632(a)(8)(B) Provide a description of mitigation actions needed to address revenue reductions and expense increases associated with activated shortage response actions. Water shortage contingency planning n/a Section 8.1 of WSCP x n/a 8.8 Section 8.8 10632(a)(8)(C) Retail Suppliers must describe the cost of compliance with Water Code Chapter 3.3, Excessive Residential Water Use During Drought . Water shortage contingency planning n/a Section 8.2 of WSCP x n/a 8.9 Section 8.9 10632(a)(9) Retail Suppliers must describe the monitoring and reporting requirements and procedures that ensure appropriate data are collected, tracked, and analyzed for purposes of monitoring customer compliance. Water shortage contingency planning n/a Section 9 of WSCP x x 8.10 Section 8.10 10632(a)(10) Describe reevaluation and improvement procedures for monitoring and evaluation the WSCP to ensure risk tolerance is adequate and appropriate water shortage mitigation strategies are implemented. Water shortage contingency planning n/a Section 10 of WSCP x n/a 8.11 Section 8.11 10632(b) Analyze and define water features that are artificially supplied with water, including ponds, lakes, waterfalls, and fountains, separately from swimming pools and spas. Water shortage contingency planning n/a Section 11 of WSCPx x 8.12 Section 8.12 10632(c) Make available the WSCP to customers and any city or county where it provides water within 30 days after adoption of the plan. Water shortage contingency planning n/a Section 12 of WSCP x n/a 9.1 Sections 9.1 10631(e)(1) Retail Suppliers shall provide a description of the nature and extent of each demand management measure implemented over the past five years. The description will address specific measures listed in code. Demand management measures n/a Ch 9 n/a x 9.2 Sections 9.2 10631(e)(2) Wholesale Suppliers shall describe specific demand management measures listed in code, their distribution system asset management program, and Supplier assistance program. Demand management measures n/a x n/a 10 Chapter 10 10608.26(a) Retail Suppliers shall conduct a public hearing to discuss adoption, implementation, and economic impact of water use targets (recommended to discuss compliance). Plan adoption, submittal, and implementation n/a x x 10.2 Section 10.2.1 10621(b) Notify, at least 60 days prior to the public hearing, any city or county within which the Supplier provides water that the Supplier will be reviewing the UWMP and considering amendments or changes to the plan. Plan adoption, submittal, and implementation 10-1 Chapter 10 x x 10.4 Section 10.4 10621(f) Each urban water Supplier shall update and submit its 2025 plan to DWR by July 1, 202 6. Plan adoption, submittal, and implementation n/a x x 10.2 Sections 10.2.2, 10.3, and 10.5 10642 Provide supporting documentation that the Supplier made the UWMP and WSCP available for public inspection, published notice of the public hearing, and held a public hearing about the UWMP and WSCP. Plan adoption, submittal, and implementation n/ax x 10.2 Section 10.2.2 10642 The Supplier is to provide the time and place of the hearing to any city or county within which the Supplier provides water. Plan adoption, submittal, and implementation 10-1x x 10.3 Section 10.3.2 10642 Provide supporting documentation that the UWMP and WSCP has been adopted as prepared or modified. Plan adoption, submittal, and implementation n/ax x 10.4 Section 10.4 10644(a) Provide supporting documentation that the Supplier has submitted their UWMP to the California State Library. Plan adoption, submittal, and implementation n/ax x 10.4 Section 10.4 10644(a)(1) Provide supporting documentation that the Supplier has submitted their UWMP to any city or county within which the Supplier provides water no later than 30 days after adoption. Plan adoption, submittal, and implementation n/ax x 10.4 Sections 10.4.1 and 10.4.2 10644(a)(2) The UWMP, or amendments to the UWMP, submitted to DWR shall be submitted electronically. Plan adoption, submittal, and implementation n/ax x 10.7 Section 10.7.2 10644(b) If revised, submit a copy of the WSCP to DWR within 30 days of adoption. Plan adoption, submittal, and implementation n/ax x 10.5 Section 10.5 10645(a) Provide supporting documentation that, not later than 30 days after filing a copy of its UWMP with DWR, the Supplier has or will make the plan available for public review during normal business hours. Plan adoption, submittal, and implementation n/ax x 10.5 Section 10.5 10645(b) Provide supporting documentation that, not later than 30 days after filing a copy of its WSCP with DWR, the Supplier has or will make the plan available for public review during normal business hours. Plan adoption, submittal, and implementation n/ax x 10.6 Section 10.6 10621(c) If Supplier is regulated by the Public Utilities Commission, include its plan and contingency plan as part of its general rate case filings. Plan adoption, submittal, and implementation n/a 3 EXHIBIT
1 ATTACHMENT B: DWR STANDARDIZED UWMP TABLES FOR
RETAIL URBAN WATER SUPPLIERS
EXHIBIT 1
Volume of
Water Supplied
2025
(AF)
CA3910012 City of Stockton 51,887 32,060
51,887 32,060
NOTES:
Submittal Table 2-1 Retail: Public Water Systems
Total
Add additional rows as needed
DWR NOTES:
Units of measure (AF, CCF, MG) must remain consistent throughout the UWMP as reported in Submittal Table 2-3. This table identifies the unit of measure selected in Table 2-3.
Has there been a change in the number of affiliated Public Water Systems since the 2020 UWMP? (OPTIONAL)
Public Water System
Number
Public Water System
Name
Number of Municipal
Connections 2025
EXHIBIT 1
Water Supplier is also a member of a SB
X7-7 Regional Alliance
NOTES:
Name of Regional Alliance or
RUWMP (Drop Down List)
Submittal Table 2-2: Plan Identification
Select
One or
Both
Type of Plan
Individual UWMP
Regional Urban Water Management Plan
(RUWMP)
EXHIBIT 1
Supplier is a wholesale supplier
Supplier is a retail supplier
UWMP Tables are in calendar years
UWMP Tables are in fiscal years
Unit AF
Submittal Table 2-3: Supplier Identification
Type of Supplier (select one or both)
Fiscal or Calendar Year (select one)
If using fiscal years provide month and date that the fiscal year begins (mm/dd)
Units of measure used in UWMP
(Select from the drop down list).
DWR NOTES:
Units of measure (AF, CCF, MG) must remain consistent
throughout the UWMP as reported in Submittal Table 2-3.
EXHIBIT 1
Submittal Table 2-4 Retail: Water Supplier Information Exchange Water Code Section 10631(h)
The retail Supplier has informed the following wholesale supplier(s) of projected water use in accordance with Water Code Section 10631 (h).
Wholesale Water Supplier Name
Add additional rows as needed
Stockton East Water District
NOTES:
10631(h) An urban water supplier that relies upon a wholesale agency for a source of water shall provide the wholesale agency with water use projections from that agency for that source of water in five-year increments to 20 years or as far as data is available.
EXHIBIT 1
2025 2030 2035 2040 2045 2050(opt)
191,302 205,478 220,705 237,060 254,627 273,496
Submittal Table 3-1 Retail: Population - Current and Projected Water Code Section 10631(a)
Population
Served
NOTES:
CWC 10631(a) describe the current and projected population of the service area including current and projected population…
EXHIBIT 1
Use Type
Volume
(AF)
Single Family Potable 15,374
Multi-Family Potable 2,927
Commercial Includes Institutional/Governmental use
type
Potable 6,083
Landscape Irrigation Potable 3,400
Sales/Transfers/Exchanges to other
Suppliers Metered to San Joaquin County Potable 931
Industrial Potable 526
Other (optional) Hydrant Meters/Jumpers Potable 70
Distribution System Water Loss Potable 2,749
32,060
0 Total 32,060
Submittal Table 4-1 Retail: 2025 Actual Total Uses for Potable and Non-Potable Water Water Code Section 10631(d)(1)
CWC 10631(d)(1) For an urban retail water supplier, quantify, to the extent records are available, past and current water use…identifying the uses among water use sectors including but not limited to:
NOTES: Volume is measured in Acre-Feet (AF)
DWR NOTES: Units of measure (AF, CCF, MG) must remain consistent throughout the UWMP as reported in Submittal Table 2-
3. This table identifies the unit of measure selected in Submittal Table 2-3. 2025 Actual Water Use
Add additional rows as needed
Level of Treatment When
Delivered (OPTIONAL)
Drop down list
Additional Description
(as needed)
Drop down list
May select each use multiple times
These are the only use types that will be recognized by the WUEdata online submittal tool
Subtotal Potable
Subtotal Non-Potable
EXHIBIT 1
Use Type
2030 2035 2040 2045 2050 (opt)
(AF) (AF) (AF) (AF) (AF)
Single Family Potable 16,481 17,668 18,940 20,303 21,765 Multi-Family Potable 3,138 3,364 3,606 3,865 4,144
Commercial Includes Institutional/Governmental
use type
Potable 6,521 6,990 7,494 8,033 8,612
Landscape Irrigation Potable 3,645 3,907 4,189 4,490 4,813 Sales/Transfers/Exchanges to other Suppliers Metered to San Joaquin County Potable 998 1,070 1,147 1,230 1,318 Industrial Potable 564 604 648 695 745
Other (optional) Hydrant Meters/Jumpers Potable 75 80 86 92 99 Distribution System Water Loss Potable 2,947 3,159 3,387 3,630 3,892 34,368 36,843 39,496 42,339 45,388
0 0 0 0 0
34,368 36,843 39,496 42,339 45,388
Add additional rows as needed.
Drop down list
May select each use multiple times
These are the only Use Types that will be recognized
by the WUEdata online submittal tool
Additional Description
(as needed) Level of Treatment
When Delivered
(OPTIONAL)
Drop down list
Submittal Table 4-2 Retail: Total Uses of Potable, and Non-PotableWater - Projected Water Code Section 10631(d)(1)
Projected Water Use
(Report To the Extent that Records are Available)
CWC 10631(d)(1) For an urban retail water supplier, quantify, to the extent records are available... projected water use…identifying the uses among water use sectors… NOTES:
Total
DWR NOTES: Units of measure (AF, CCF, MG) must remain consistent throughout the UWMP as reported in Submittal Table 2-3. This table identifies the unit of measure selected in Submittal Table 2-3.
Subtotal Non-Potable
Subtotal Potable
EXHIBIT 1
Are Future Water Savings Included in Projections?
(Refer to Appendix K of UWMP Guidebook)
Drop down list (y/n)
Yes
If "Yes" to above:
State the section or page number, in the cell to the right, where citations of the codes, ordinances, or otherwise are utilized in demand projections are found.
OPTIONAL Suppliers may complete Optional Submittal Table 4-4 R to quantify the expected savings.
California Code of Regulations, Title
23 Waters, Division 2 DWR,
Chapter 2.7 Model Water Efficient
Landscape Ordinance (MWELO),
updated 2015
Are Lower Income Residential Demands Included In Projections? (Refer to Appendix K of UWMP Guidebook)
Drop down list (y/n)
Yes
OPTIONAL If the method for accounting Lower Income Residential Demands has been included, provide page number where this accounting can be found. (An example is included in Appendix K.)
Submittal Table 4-3 Retail: Inclusion in Water Use Projections Water Code Section 10631 (a), 10631 (d)(4)(A), and 10631 (d)(4)(B) NOTES:
CWC 10631 (d) (4) (B) to the extent that an urban water supplier reports the information described in subparagraph (A), an urban water supplier shall do both of the following:
(i) Provide citations of the various codes, standards, ordinances or transportation and land use plans utilized in making the projections. (ii) Indicate the extent that the water use projections consider savings from codes, standards, ordinances, or transportation and land use plans. Water use projections that do not account for these water savings shall be noted of that fact.
CWC 10631(a) Water use projections required by section 10631 shall include projected water use for single-family and multifamily residential housing needed for lower income households, as identified in the housing element of any city, county, or city and county, in the service area of the supplier .
CWC10631 (d) (4) (A) Water use projections, where available, shall display and account for water savings estimated to result from adopted codes, standards, ordinances, or transpotation and land use plans identified by the urban water supplier, as applicable to the service area.
EXHIBIT 1
Public Water System ID # Reported
in Table 2-1 R Reporting Period Submitted to DWR Water Loss Audit Program (yes/no) 2020 Yes
2021 Yes
2022 Yes
2023 Yes
2024 Yes
CWC 10631(d)(3) (A) The distribution system water loss shall be quantified for each of the five years preceding the plan update, in accordance with rules adopted pursuant to Section 10608.34.
Submittal Table 4-5 Retail: Water Loss Audit Reporting
Water Code Section 10631(d)(3)(A)
DWR NOTES: Suppliers will provide a link to the WUEdata submittals of their Water Loss Audit Reports.
NOTES: Gap in water loss audit data from 1/1/21 to 6/30/21 Report submittal status for all five years for each Public Water System as available.
Add rows as needed
EXHIBIT 1
Volume of Total Real
Loss (from AWWA
Water Loss Audit)
Volume of Total
Apparent Loss
(from AWWA Water
Loss Audit)
(AF)
(AF)
CA3910012 Yes 16.5
Gallons per
Service
Connection per
Day (GPSCD)
51730 1007.8
17.4 11.7
Gallons per
Service
Connection per
Day (GPSCD)
51730 597.4
10.3 Number of
Connections
CWC 10631(d)(3)(C) In the plan due July 1, 2021, and in each update thereafter, data shall be included to show whether the urban retail water supplier met the distribution loss standards enacted by the board pursuant to Section 10608.34.
Submittal Table 4-6 Retail: Progress Towards 2028 Water Loss Standard Water Code Section 10631(d)(3)(C) NOTES:
Apparent Water Loss
Did the Water Board Calculate a
Water Loss Standard for this
Public Water System? (y/n)
If no, Supplier will not complete
this row.
Real Water Loss
Water Board's Calculated Water Loss Standards
DWR NOTES: Units of measure (AF, CCF, MG) for Water Loss MUST remain consistent with units reported in Submittal Table 2-3. The units reported in Submittal Table 2-3 are used in this table's calculations.
Public Water
System ID #
Reported in
Submittal Table 2-1
R
Add additional rows as needed.
Most Recent AWWA Water Loss Audit
Real Water
Loss Per Unit
per Day
Most Recent AWWA Water Loss Audit
Apparent Water
Loss Per Unit per
Day
Number of Units
(Connections or Miles
corresponding with
units selected)
State Water Board Standard
2028 Real Water Loss
Standard per Unit per
day
Units for Real
Water Loss
Drop down list
State Water Board Standard
2028 Apparent
Water Loss Standard
per Unit per Day
Units for
Apparent Water
Loss
EXHIBIT 1
Actual 2025 GPCD
(From SB X7-7
Compliance Form)
Did Supplier meet
the 2020 Target in
2025?
No Individual Target 165 158 Yes NA
10608.40 Urban water retail suppliers shall report to the department on their progress in meeting their urban water use targets as part of their urban water management plans submitted pursuant to Section 10631.
Submittal Table 5-1 Retail: SB X7-7 2020 Target Progress Water Code Section 10608.40
NOTES:
Did Supplier
Achieve Targeted
Reduction for
2020?
2020 Target Actual 2020 GPCD
Regional Alliance
Target or
Individual
Target?
Drop down list
DWR NOTES:
Suppliers calculating a 2025 GPCD will need to complete and submit SB X 7-7 Compliance Tables to verify the use of SB X7-7 Methodologies.
Suppliers that were part of a merger or consolidation since 2020 see Chapter 5 and Appendix P for guidance.
NA=Not Applicable
Check the box if the Supplier was not an Urban Water Supplier during or before the 2020 UWMP reporting cycle.
Proceed to the next table.
Only for suppliers that did not meet the
Target in 2020
See DWR NOTES below.
Was Supplier part of a
merger or
consolidation since
2020?
EXHIBIT 1
2021 2022 2023 2024 2025
(AF) (AF) (AF) (AF) (AF)
Alluvial Basin Non-Potable San Joaquin Valley Basin,
Eastern San Joaquin Subbasin 7089 1547 2430 1066 956
7,089 1,547 2,430 1,066 956
Add additional rows as needed
10631(4) If groundwater is identified as an existing or planned source of water available to the supplier, all of the following information:
(C) A detailed description and analysis of the location, amount, and sufficiency of groundwater pumped by the urban water supplier for the past five years. The description and analysis shall be based on information that is reasonably available, including, but not limited to, historic use records.
Submittal Table 6-1 Retail: Groundwater Volume Pumped
Water Code Section 10631(4) and 10631(4)(c)
DWR NOTES:
Units of measure (AF, CCF, MG) must remain consistent throughout the UWMP as reported in Submittal Table 2-3. This table identifies the unit of measure selected in Submittal Table 2-3.
NOTES
Total
Check the box if the Supplier does not pump groundwater.
Proceed to the next table.
Check the box if all or part of the groundwater described below is desalinated. (OPTIONAL) Groundwater Type
Drop Down List
May use each category
multiple times
Water Type
(OPTIONAL)
Drop down list
Location or Basin Name
EXHIBIT 1
Volume of
Wastewater
Collected from
UWMP Service
Area 2025
(AF)
COSMUD Metered 4,910 Stockton Regional WW Control
Facility, Place ID 258739 Yes
4,910
CWC 10633 (a) (a) A description of the wastewater collection and treatment systems in the supplier’s service area, including a quantification of the amount of wastewater collected and treated and the methods of wastewater disposal.
Check the box if there is no wastewater collection system.
Proceed to the next table.
NOTES: Units are in acre-feet (AF). Collected wastewater volume includes that which is produced by Cal Water and San Joaquin County service areas since they are not metered seperately.
Submittal Table 6-2 Retail: Wastewater Collected Within Service Area in 2025 Water Code Section 10633(a)
Percentage of 2025 service area population served by wastewater collection system (OPTIONAL)
Percentage of 2025 service area served by wastewater collection system (OPTIONAL) DWR NOTES: Units of measure (AF, CCF, MG) must remain consistent throughout the UWMP as reported in Submittal Table 2-3. This table identifies the unit of measure selected in Submittal Table 2-3.
Additional Guidance. See Appendix M, Section M.21 for detailed guidance on this table.
Wastewater Collection Recipient of Collected Wastewater Total Wastewater Received from UWMP
Service Area in 2025:
Wastewater
Volume Metered
or Estimated?
OPTIONAL
Drop Down List
Name of Wastewater Treatment
Plant (WWTP) and Place ID
Number
Drop down list
Is WWTP Located
Within UWMP
Area?
Drop Down List
Add additional rows as needed
Name of Wastewater
Collection Agency
EXHIBIT 1
Volume Volume Volume Volume Volume
(AF) (AF) (AF) (AF) (AF) (AF) (AF)
Stockton Regional WW
Control Facility, Place ID
Yes 11,077 9,413 0 0 0
11,077 9,413 0 0 0 0 0
Submittal Table 6-3 Retail: Wastewater Treatment and Outcomes Within UWMP Service Area in 2025 Water Code Section 10633(a)
DWR NOTES:
Units of measure (AF, CCF, MG) must remain consistent throughout the UWMP as reported in Submittal Table 2-3. This table identifies the unit of measure selected in Submittal Table 2-3.
IPR: Indirect Potable Reuse would have the treatment level of its end use requrement in the Level of Treatment drop-down.
Additional Guidance. See Appendix M, Section M.21 for detailed guidance on this table.
Water Recycled Outside
of UWMP Service Area
(enter data as applicable)
Effluent Discharge that is
not a Permitted Recycled
Water Use
(enter data as applicable)
Required Discharge for
Instream Flow
(enter data as applicable)
Delivered to Another Entity for Additional
Treatment
(enter data as applicable)
Add additional rows as needed
10633. The plan shall provide, to the extent available, information on recycled water and its potential for use as a water source in the service area of the urban water supplier...and shall include all of the following:
(b) A description of the quantity of treated wastewater that meets recycled water standards, is being discharged, and is otherwise available for use in a recycled water project. 2025 Outcomes of Treated Wastewater
Check the box if no wastewater is treated or disposed of within the UWMP service area.
Proceed to the next table.
Does This Plant
Treat
Wastewater
Generated
Outside the
UWMP Service
Area?
(OPTIONAL)
Drop down list
Wastewater Treatment
Plant Name and Place
ID Number
Drop down list
Treatment Level
Drop down list
Treatment Level
Drop down list
Treatment Level
Drop down list
Treatment Level
Drop down list
Treatment Level
Drop down list
Name of other
entity
Total 2025
Volume of
Water
Treated
NOTES: Units are in acre-feet (AF). Volumes of treated wastewater and discharged wastewater are provided by Wastewater Operations QOR Sharepoint.
Total
2025 Volume of
Wastewater
Received from
UWMP Service
Area
(As Reported in
Submittal Table
6-2 R )
Water Recycled Within
UWMP Service Area
(enter data as applicable)
EXHIBIT 1
2025 2030 2035 2040 2045 2050 (opt)
(AF) (AF) (AF) (AF) (AF) (AF) Volume Narrative page number (OPTIONAL)
Agricultural irrigation - - - - - - - -
Landscape irrigation (exc golf
courses) - - - - - - - -
Golf course irrigation - - - - - - - -
Commercial use - - - - - - - -
Industrial use - - - - - - - -
Geothermal and other energy
production - - - - - - - -
Recreational impoundment - - - - - - - -
Wetlands or wildlife habitat - - - - - - - -
Groundwater recharge (IPR) - - - - - - - -
Reservoir water augmentation
(IPR) - - - - - - - -
Direct potable reuse - - - - - - - -
Other (Description Required) - - - - - - - -
0 0 0 0 0 0 0 0
Name of Supplier Operating the Recycled Water Distribution System (OPTIONAL) :
Supplemental Water Added in 2025 (volume) Include units (OPTIONAL) :
Source of 2025 Supplemental Water (OPTIONAL) :
Check box if recycled water is not used and is not planned for use within the service area of the supplier. The supplier will only complete the column on "Potential Recycled Water Use" and submit an accompanying narrative on the feasibility of that potential recycled water use.
Submittal Table 6-4 Retail: Recycled Water Direct Beneficial Uses Within Service Area Water Code Section 10633 (c)(e)
10633. The plan shall provide, to the extent available, information on recycled water and its potential for use as a water source in the service area of the urban water supplier... and shall include...
(c) A description of the recycled water currently being used in the supplier’s service area, including, but not limited to, the type, place, and quantity of use
Total
Use Type
Drop down list
Water Type
(after treatment if
treated)
(OPTIONAL)
Drop down list
Additional Information
(as needed)
Potential Recycled Water Use
Add additional rows as needed
DWR NOTES: Units of measure (AF, CCF, MG) must remain consistent throughout the UWMP as reported in Submittal Table 2-3. This table identifies the unit of measure selected in Submittal Table 2-3.
Additional Guidance. See Appendix M, Section M.21 for detailed guidance on this table.
Potential recycled water use - a description of the feasibility of these uses must be included in the narrative.
Multiple Producers: If you have multiple recycled water producers, submit a separate table for each.
NOTES:
Name(s) of Facility/ies Producing (Treating) the Recycled Water (OPTIONAL) :
EXHIBIT 1
2020 Projection
for 2025
2025 Actual
Use
(AF) (AF)
- -
- -
- -
- -
- -
- -
- -
- -
- -
- -
- -
- -
- -
0 0
Submittal Table 6-5 Retail: 2020 UWMP Recycled Water Use Projection Compared to 2025 Actual
Water Code Section 10633 (e)
Check the box if recycled water was not used in 2025 nor previously projected for use in 2020.
Proceed to the next table.
Add additional rows as needed
Agricultural irrigation
NOTES:
Total
DWR NOTES:
Units of measure (AF, CCF, MG) must remain consistent throughout the UWMP as reported in Submittal Table 2-3. This table identifies the unit of measure reported in Submittal Table 2-3 Additional Guidance. See Appendix M, Section M.21 for detailed guidance on this table.
Use Type
Drop Down list
10633. The plan shall provide, to the extent available, information on recycled water and its potential for use as a water source in the service area of the urban water supplier. The preparation of the plan shall be coordinated with local water, wastewater, groundwater, and planning agencies that operate within the supplier’s service area, and shall include all of the following: (e) ...a description of the actual use of
recycled water in comparison to uses previously projected pursuant to this subdivision Direct potable reuse
Other (Description Required)
Reservoir water augmentation (IPR)
Landscape irrigation (exc golf courses)
Golf course irrigation
Wetlands or wildlife habitat
Groundwater recharge (IPR)
Commercial use
Industrial use
Geothermal and other energy production
Seawater intrusion barrier
Recreational impoundment
EXHIBIT 1
Expected Increase in Recycled Water
Use
(AF)
(AF) 0
10633. The plan shall provide, to the extent available, information on recycled water and its potential for use as a water source in the serv`ice area of the urban water supplier. The preparation of the plan shall be coordinated with local water, wastewater, groundwater, and planning agencies that operate within the supplier’s service area, and shall include all of the following:
(f) a description of actions, including financial incentives, which may be taken to encourage the use of recycled water, and the projected results of these actions in terms of acre feet of recycled water used per year.
DWR NOTES:
Units of measure (AF, CCF, MG) MUST remain consistent with units reported in Submittal Table 2-3. The units reported in Submittal Table 2-3 are used in this table's calculations.
The unit conversion to Acre Feet addresses the Water Code's requirement that this value be provided in acre-feet.
NOTES:
Submittal Table 6-6 Retail: Methods to Encourage Future Recycled Water Use Water Code Section 10633 (f)
Check the box if the Supplier does not plan to expand recycled water use in the future. Supplier will not complete the table below but will provide narrative explanation.
Provide page location of narrative in the UWMP
Add additional rows as needed
Total
Name of Action Description Planned Implementation Year
EXHIBIT 1
(AF)
North Stockton Pipeline
Hypochlorite Facility
Project (a)
Yes SEWD
Construct new sodium
hypchlorite injection
system to combine supply
from the DWTP and SEWD
Potable Completed in 2021 All Year Types
Increase WID Supply (b) Yes WID
Per contract, WID would
supply the City with an
additional 3.0 AFY per acre
the City annexed
Non-Potable 2030 All Year Types 6500 AFY
Advanced Metering
Infrastructure (c) No -
Provide greater efficiency
and reduce costs for
meter reading and allow
customers to better track
and manage their water
use
2025-2028 All Year Types
Water Type
(after treatment if
treated)
(OPTIONAL)
Drop Down list
Planned for Use in
Year Type
Drop Down List
NOTES: Units are in acre-feet (AF).
(a) The project will increase supply reliability by allowing North Stockton to be supplied by the DWTP and SEWD without formation of undesireable disinfection byproducts due to different potable water treatment processes. (b) WID supply may increase by an additional 6,500 AFY as agricultrual lands north of the City are annexed to the City. (c) AMI will provide customers with the ability to access and better manage their water use.
Submittal Table 6-7 Retail: Expected Future Water Supply Projects or Programs Water Code Section 10631 (f)
DWR NOTES:
Units of measure (AF, CCF, MG) must remain consistent throughout the UWMP as reported in Submittal Table 2-3. This table identifies the unit of measure reported in Submittal Table 2-3.
Check the box if some or all of the supplier's future water supply projects or programs are not compatible with this table and are described in a narrative format.
Check the box if there are no expected future water supply projects or programs that provide a quantifiable increase to the agency's water supply.
Procees to the next table.
Planned
Implementation
Year
Add additional rows as needed
Joint Project with other suppliers? Expected
Increase in
Water Supply
to Supplier
(This may be a
range)
Provide page location of narrative in the UWMP
Name of Future Projects
or Programs Drop Down
List
(yes/no)
If Yes, Supplier Name
Additional Description
(as needed)
EXHIBIT 1
Water Supply
Actual Volume
Total Entitlement
(OPTIONAL)
See "DWR Notes" below
(AF) (AF)
Purchased or Imported Water SEWD Potable 16,571
Purchased or Imported Water WID Potable 9,341
Surface water (not desalinated) San Jaoquin River Diversion Potable 4,910 Groundwater (not desalinated) City-owned wells Potable 956 31,778 0
0 0
31,778 0
10631. A plan shall be adopted in accordance with this chapter that shall do all of the following... (b) Identify and quantify, to the extent practicable, the existing and planned sources of water available to the supplier over the same five-year increments described in subdivision (a), providing supporting and related information...
Submittal Table 6-8 Retail: Water Supplies — 2025 Actual Water Code Section 10631 (b)
2025
NOTES: Units are in acre-feet (AF).
DWR NOTES:
Units of measure (AF, CCF, MG) must remain consistent throughout the UWMP as reported in Submittal Table 2-3. This table identifies the unit of measure selected in Submittal Table 2-3.
Total Entitlement: e.g. Water Right, Groundwater Allocation, Contracted Amount.
Add additional rules as needed
Total
Subtotal Potable
Subtotal Non-Potable
Drop down list
May use each category multiple times.
These are the only water supply
categories that will be recognized by the
WUEdata online submittal tool
Additional Description
(as needed)
Water Type
(after treatment if
treated)
(OPTIONAL)
Drop Down list
EXHIBIT 1
Water Supply
Additional
Detail on
Water
Supply
Water Type
(after treatment if
treated)
(OPTIONAL)
Drop Down list
Projected Water Supply (Report to the Extent Practicable) Drop down list
May use each category multiple
times. These are the only water
supply categories that will be
recognized by the WUEdata online
submittal tool
2030 2035 2040 2045 2050 (opt)
Reasonably
Available
Volume
Total Entitlement
(OPTIONAL)
See "DWR Notes"
below
Reasonably
Available
Volume
Total Entitlement
(OPTIONAL)
See "DWR Notes"
below
Reasonably
Available
Volume
Total Entitlement
(OPTIONAL)
See "DWR Notes"
below
Reasonably
Available
Volume
Total Entitlement
(OPTIONAL)
See "DWR Notes"
below
Reasonably
Available
Volume
Total Entitlement
(OPTIONAL)
See "DWR Notes"
below
(AF) (AF) (AF) (AF) (AF) (AF) (AF) (AF) (AF) (AF)
Add additional rows as needed
Purchased or Imported
Water
SEWD 20,000 20,000 20,000 20,000 20,000
Purchased or Imported
Water
WID 8,850 9,850 10,850 11,850 13,000
Surface water (not
desalinated)
San Joaquin
River
Diversion
24,800 25,000 25,000 25,000 25,000
Groundwater (not
desalinated)
City-owned
wells 15,400 15,400 15,400 15,400 15,400
Subtotal Potable 0 0 0 0 0 0 0 0 0 0
Subtotal Non-Potable 0 0 0 0 0 0 0 0 0 0
Total 69,050 0 70,250 0 71,250 0 72,250 0 73,400 0
10631. A plan shall be adopted in accordance with this chapter that shall do all of the following... (b) Identify and quantify, to the extent practicable, the existing and planned sources of water available to the supplier over the same five-year increments described in subdivision (a), providing supporting and related information, including all of the following Submittal Table 6-9 Retail: Water Supplies — Projected
Water Code Section 10631 (b)
DWR NOTES:
Units of measure (AF, CCF, MG) must remain consistent throughout the UWMP as reported in Submittal Table 2-3.
Total Entitlement: e.g. Water Right, Groundwater Allocation, Contracted Amount.
NOTES: Units are in acre-feet.
1. The Second Amended Wholesale Water Supply Contract (2nd Amended Contract) between SEWD and the City of Stockton, Cal Water and San Joaquin County (Urban Contractors) is due to expire on April 1, 2035. The projected reasonably available water supply totals listed in Table 6-14 (DWR Table 6-9 Retail) after the contract expiration date are based on terms specified under the 2nd Amended Contract, Section 3. Renewal: Continued Service where each Contractor shall be entitled to continued service, if desired by a Contractor(s), and to extend or renew the terms and conditions of the Contract. Specific terms and conditions for this continued service would be based on agreement between SEWD and Contractor(s).
2. Because of the uncertainty of the timpacts of the Bay-Delta Water Quality Control Plan Amendment, projected SEWD supplies are assumed to remain at the current reasonably available volume.
EXHIBIT 1
Water Delivery Product
drop down list
(If delivering more than one type of product recommend using Table O-1C)
Retail Potable
Deliveries
Start Date of Reporting Period 1/1/2025
End Date of Reporting Period 12/31/2025
Is upstream embedded energy in the values reported?
Units of Measure for Water
(AF) Total Utility
See DWR NOTES
Hydropower Net Utility
29,311 - 29,311
8,065,961 8,065,961 -
275 - 275
Quantity of Self-Generated Renewable Energy
Data Quality (Estimate, Metered Data, Combination of Estimates and Metered Data) Data Quality Narrative:
Narrative:
Optional Submittal Table O-1B: Recommended Energy Reporting - SINGLE DELIVERY PRODUCT - TOTAL UTILITY
APPROACH
Energy consumption was provided for the groundwater wells, reservoir pump and booster stations, San Joaquin River intake, and the DWTP.
Only for Water Delivery Products Under the Urban Water Supplier's Operational Control
Sum of All Water Management
Processes
Non-Consequential Hydropower
DWR NOTES:
Total Utility:The volume of water entered in the “Total Utility” column should equal the volume of water entering the distribution system (excluding recycled water); in most cases, this is the total volume calculated in UWMP Table 4-1: 2025 Actual Total Uses for Potable and Non-Potable Water. Note if recycled water is included in your Submittal Table 4-1, you must exclude it from your volume in this table. 179887 kWh
NOTES:
The water service area is supplied by surface water from the San Joaquin River, purchased water from SEWD and WID, and groundwater from City‑owned production wells. An overview of each water supply source is provided in Section 6.3. Energy data summarize monthly energy consumption associated with operation of the Delta Water Treatment Plant (DWTP), groundwater wells, and reservoirs, with limited on‑site solar generation at the DWTP.
Volume of Water Entering Process
Energy Consumed (kWh)
Energy Intensity (kWh/AF)
Metered Data
EXHIBIT 1
Average Year 2020 100%
Single-Dry Year 2019 100%
Consecutive Dry Years 1st Year 2015 100%
Consecutive Dry Years 2nd Year 2016 100%
Consecutive Dry Years 3rd Year 2017 100%
Consecutive Dry Years 4th Year 2018 100%
Consecutive Dry Years 5th Year 2019 100%
OPTIONAL Submittal Table 7-1 Retail: Basis of Water Year Data (Reliability Assessment) Year Type
Base Year
If not using a calendar
year, type in the last
year of the fiscal,
water year, or range
of years, for example,
water year 2024-
2025, use 2025
Available Supplies if
Year Type Repeats
Check the box if quantification of available supplies is not compatible with this table and is provided elsewhere in the UWMP.
Location: [insert location from UWMP]
Quantification of available supplies is provided in this table as either volume only, percent only, or both.
Volume Available % of Average Supply
15400
15400
DWR NOTES: Supplier may use multiple versions of Submittal Table 7-1 R if different water sources have different base years and the supplier chooses to report the base years for each water source separately. If a Supplier uses multiple versions of Submittal Table 7-1 R, in the "Note" section of each submittal table, state that multiple versions of Submittal Table 7-1 R are being used and identify the particular water source that is being reported in each submittal table.
Units of measure (AF, CCF, MG) must remain consistent throughout the UWMP as reported in Submittal Table 2-3. This table reports the units of measure reported in Submittal Table 2-3.
NOTES: Units are in acre-feet (AF).
15400
15400
15400
15400
15400
15400
EXHIBIT 1
Average Year 2021 100%
Single-Dry Year 2017 83%
Consecutive Dry Years 1st Year 2015 77%
Consecutive Dry Years 2nd Year 2016 83%
Consecutive Dry Years 3rd Year 2017 95%
Consecutive Dry Years 4th Year 2018 101%
Consecutive Dry Years 5th Year 2019 28562 105%
DWR NOTES: Supplier may use multiple versions of Submittal Table 7-1 R if different water sources have different base years and the supplier chooses to report the base years for each water source separately. If a Supplier uses multiple versions of Submittal Table 7-1 R, in the "Note" section of each submittal table, state that multiple versions of Submittal Table 7-1 R are being used and identify the particular water source that is being reported in each submittal table.
Units of measure (AF, CCF, MG) must remain consistent throughout the UWMP as reported in Submittal Table 2-3. This table reports the units of measure reported in Submittal Table 2-3.
NOTES: Units are in acre-feet (AF).
27200
22500
20983
22649
25778
27564
OPTIONAL Submittal Table 7-1 Retail: Basis of Water Year Data (Reliability Assessment) Year Type
Base Year
If not using a calendar
year, type in the last
year of the fiscal,
water year, or range
of years, for example,
water year 2024-
2025, use 2025
Available Supplies if
Year Type Repeats
Check the box if quantification of available supplies is not compatible with this table and is provided elsewhere in the UWMP.
Location: [insert location from UWMP]
Quantification of available supplies is provided in this table as either volume only, percent only, or both.
Volume Available % of Average Supply
27200
EXHIBIT 1
Average Year 2021 100%
Single-Dry Year 2020 46%
Consecutive Dry Years 1st Year 2012 46%
Consecutive Dry Years 2nd Year 2013 90%
Consecutive Dry Years 3rd Year 2014 54%
Consecutive Dry Years 4th Year 2015 52%
Consecutive Dry Years 5th Year 2016 9913 112%
DWR NOTES: Supplier may use multiple versions of Submittal Table 7-1 R if different water sources have different base years and the supplier chooses to report the base years for each water source separately. If a Supplier uses multiple versions of Submittal Table 7-1 R, in the "Note" section of each submittal table, state that multiple versions of Submittal Table 7-1 R are being used and identify the particular water source that is being reported in each submittal table.
Units of measure (AF, CCF, MG) must remain consistent throughout the UWMP as reported in Submittal Table 2-3. This table reports the units of measure reported in Submittal Table 2-3.
NOTES: Units are in acre-feet (AF).
8850
4080
4080
7993
4760
4628
OPTIONAL Submittal Table 7-1 Retail: Basis of Water Year Data (Reliability Assessment) Year Type
Base Year
If not using a calendar
year, type in the last
year of the fiscal,
water year, or range
of years, for example,
water year 2024-
2025, use 2025
Available Supplies if
Year Type Repeats
Check the box if quantification of available supplies is not compatible with this table and is provided elsewhere in the UWMP.
Location: [insert location from UWMP]
Quantification of available supplies is provided in this table as either volume only, percent only, or both.
Volume Available % of Average Supply
8850
EXHIBIT 1
Average Year 2018 100%
Single-Dry Year 2015 91%
Consecutive Dry Years 1st Year 2012 92%
Consecutive Dry Years 2nd Year 2013 95%
Consecutive Dry Years 3rd Year 2014 95%
Consecutive Dry Years 4th Year 2015 91%
Consecutive Dry Years 5th Year 2016 107%
OPTIONAL Submittal Table 7-1 Retail: Basis of Water Year Data (Reliability Assessment) Year Type
Base Year
If not using a calendar
year, type in the last
year of the fiscal,
water year, or range
of years, for example,
water year 2024-
2025, use 2025
Available Supplies if
Year Type Repeats
Check the box if quantification of available supplies is not compatible with this table and is provided elsewhere in the UWMP.
Location: [insert location from UWMP]
Quantification of available supplies is provided in this table as either volume only, percent only, or both.
Volume Available % of Average Supply
19900
21300
DWR NOTES: Supplier may use multiple versions of Submittal Table 7-1 R if different water sources have different base years and the supplier chooses to report the base years for each water source separately. If a Supplier uses multiple versions of Submittal Table 7-1 R, in the "Note" section of each submittal table, state that multiple versions of Submittal Table 7-1 R are being used and identify the particular water source that is being reported in each submittal table.
Units of measure (AF, CCF, MG) must remain consistent throughout the UWMP as reported in Submittal Table 2-3. This table reports the units of measure reported in Submittal Table 2-3.
NOTES: Units are in acre-feet (AF).
19900
18150
18300
19000
19000
18100
EXHIBIT 1
2030 2035 2040 2045 2050 (Opt)
(AF) (AF) (AF) (AF) (AF)
Supply totals
(autofill from Submittal Table 6-
9 R)
76,250 77,450 78,450 79,450 80,600
SEWD 27,200 27,200 27,200 27,200 27,200
WID 8,850 9,850 10,850 11,850 13,000
San Joaquin River 24,800 25,000 25,000 25,000 25,000
COSMUD Wells 15,400 15,400 15,400 15,400 15,400
Use totals
(autofill from Submittal Table 4-
2 R)
29,768 30,233 30,704 31,183 31,670
Surplus/(shortfall) 46,482 47,217 47,746 48,267 48,930
WSCP - supply augmentation
benefit
WSCP - use reduction savings
benefit
Revised Surplus/(shortfall)
OPTIONAL Planned WSCP Actions
Submittal Table 7-2 Retail: Normal Year Supply and Use Comparison Water Code Section 10635 (a)
NOTES: Units are in AF (acre-feet).
DWR NOTES : Units of measure (AF, CCF, MG) must remain consistent throughout the UWMP as reported in Submittal Table 2-3.
EXHIBIT 1
2030 2035 2040 2045 2050 (Opt)
(AF) (AF) (AF) (AF) (AF)
Supply totals 64,830 64,830 64,830 64,830 64,830
SEWD 27,200 27,200 27,200 27,200 27,200
WID 4,080 4,080 4,080 4,080 4,080
San Joaquin River 18,150 18,150 18,150 18,150 18,150
COSMUD Wells 15,400 15,400 15,400 15,400 15,400
Demand Totals 29,768 30,233 30,704 31,183 31,670
Surplus/(shortfall) 35,062 34,597 34,126 33,647 33,160
WSCP - supply
augmentation benefit
WSCP - use reduction
savings benefit
Revised Surplus/(shortfall)
10635. (a) Every urban water supplier shall include, as part of its urban water management plan, an assessment of the reliability of its water service to its customers during normal, dry, and multiple dry water years. This water supply and demand assessment shall compare the total water supply sources available to the water supplier with the long-term total projected water use over the next 20 years, in fiveyear increments, for a normal water year, a single dry water year, and a drought lasting five consecutive water years.
DWR NOTES : Units of measure (AF, CCF, MG) must remain consistent throughout the UWMP as reported in Submittal Table 2-3.
NOTES
Submittal Table 7-3 Retail: Single Dry Year Supply and Use Comparison Water Code Section 10635(a)
OPTIONAL Planned WSCP Actions
EXHIBIT 1
2030 2035 2040 2045 2050 (Opt)
(AF) (AF) (AF) (AF) (AF)
Supply Totals 58,763 58,763 58,763 58,763 58,763
SEWD 20,983 20,983 20,983 20,983 20,983
WID 4,080 4,080 4,080 4,080 4,080
San Joaquin River 18,300 18,300 18,300 18,300 18,300
COSMUD Wells 15,400 15,400 15,400 15,400 15,400
Demand Totals 29,768 30,233 30,704 31,183 31,670
Surplus/(shortfall) 28,995 28,530 28,059 27,580 27,093
Supply Totals 65,042 65,042 65,042 65,042 65,042
SEWD 22,649 22,649 22,649 22,649 22,649
WID 7,993 7,993 7,993 7,993 7,993
San Joaquin River 19,000 19,000 19,000 19,000 19,000
COSMUD Wells 15,400 15,400 15,400 15,400 15,400
Demand Totals 30,468 31,293 31,293 31,183 31,670
Surplus/(shortfall) 34,574 33,749 33,749 33,859 33,372
Supply Totals 64,938 64,938 64,938 64,938 64,938
SEWD 25,778 25,778 25,778 25,778 25,778
WID 4,760 4,760 4,760 4,760 4,760
San Joaquin River 19,000 19,000 19,000 19,000 19,000
COSMUD Wells 15,400 15,400 15,400 15,400 15,400
Demand Totals 31,168 32,353 32,353 31,183 31,670
Surplus/(shortfall) 33,770 32,585 32,585 33,755 33,268
Supply Totals 66,592 66,592 66,592 66,592 66,592
SEWD 27,564 27,564 27,564 27,564 27,564
WID 4,628 4,628 4,628 4,628 4,628
San Joaquin River 19,000 19,000 19,000 19,000 19,000
COSMUD Wells 15,400 15,400 15,400 15,400 15,400
Demand Totals 31,868 33,413 33,413 31,183 31,670
Surplus/(shortfall) 34,724 33,179 33,179 35,409 34,922
Supply Totals 72,875 72,875 72,875 72,875 72,875
SEWD 28,562 28,562 28,562 28,562 28,562
WID 9,913 9,913 9,913 9,913 9,913
San Joaquin River 19,000 19,000 19,000 19,000 19,000
COSMUD Wells 15,400 15,400 15,400 15,400 15,400
Demand Totals 32,568 34,473 34,473 31,183 31,670
Surplus/(shortfall) 40,307 38,402 38,402 41,692 41,205
NOTES: Units are in acre-feet (AF)
First year
Submittal Table 7-4 Retail: Multiple Dry Years Supply and Use Comparison Water Code Section 10635(a)
Second year
Third year
Fifth year
DWR NOTES: Units of measure (AF, CCF, MG) must remain consistent throughout the UWMP as reported in Submittal Table 2-3.
Fourth year
EXHIBIT 1
Total
Total Water Use (AF) 32,352
Total Supplies (AF) 58,763
26,411
Total
Total Water Use (AF) 32,845
Total Supplies (AF) 65,042
32,197
Total
Total Water Use (AF) 33,345
Total Supplies (AF) 64,938
31,593
Total
Total Water Use (AF) 33,853
Total Supplies (AF) 65,692
31,839
Total
Total Water Use (AF) 34,368
Total Supplies (AF) 75,175
40,807
2030
Surplus/Shortfall w/o WSCP Action
DWR NOTES: Units of measure (AF, CCF, MG) must remain consistent throughout the NOTES: Units are in acre-feet (AF)
2028
2026
Surplus/Shortfall w/o WSCP Action
Surplus/Shortfall w/o WSCP Action
Surplus/Shortfall w/o WSCP Action
Surplus/Shortfall w/o WSCP Action
2027
2029
EXHIBIT 1
Standard Shortage
Levels
Percent Shortage
Range
Suppliers
Shortage
Levels
Percent
Shortage Range
1 Up to 10%
2 Up to 20%
3 Up to 30%
4 Up to 40%
5 Up to 50%
6 >50%
Submittal Table 8-1: Cross-reference for Standard vs Supplier Shortage Levels
Water Code Section 10632(a)(3)(B)
Check the box if the Supplier uses the Standard
six levels of water shortage.
Proceed to the next table.
NOTES:
EXHIBIT 1
Yes
Shortage Gap Reduction
Value
(May be a range)
(AF)
4 Exchanges Volume Up to Shortage Gap Neighboring agencies 4 Transfers Volume Up to Shortage Gap Potentially from Woodbridge Irrigation District
5 Exchanges Volume Up to Shortage Gap Neighboring agencies 5 Transfers Volume Up to Shortage Gap Potentially from Woodbridge Irrigation District
6 Exchanges Volume Up to Shortage Gap Neighboring agencies 6 Transfers Volume Up to Shortage Gap Potentially from Woodbridge Irrigation District
(E) For each action, an estimate of the extent to which the gap between supplies and demand will be reduced by implementation of the action.
Submittal Table 8-2 Retail: Supply Augmentation and Other Actions Water Code Section 10632(a)(4)(A),(C) and (E)
Add additional rows as needed
NOTES:
Is the Supplier completing this table using the standard six levels? (yes/no) 10632(a)(4) Shortage response actions that align with the defined shortage levels and include, at a minimum, all of the following:
(A) Locally appropriate supply augmentation actions.
(C) Locally appropriate operational changes.
How much is this going to reduce the
shortage gap?
DWR NOTES: Units of measure (AF, CCF, MG) must remain consistent throughout the UWMP as reported in Submittal Table 2-3.
Shortage
Level
Supply Augmentation Methods and
Other Actions by Water Supplier
Drop down list
These are the only categories that will be
accepted by the WUEdata online submittal tool
Volume or
Percentage
Drop down
Additional Explanation or Reference
(OPTIONAL)
EXHIBIT 1
Yes
Shortage Gap
Reduction Value
(May be a range)
(AF)
1 Expand Public Information Campaign Percentage 7-8% City to encourage water customers and users to implement water conservation practices No
1 Other - Prohibit use of potable water
for washing hard surfaces Percentage 0-1% Washing of Street, driveways, sidewalks, buildings Yes 1 Water Features - Restrict water use for
decorative water features, such as
fountains
Percentage 0-1% Only recirculated water can be used in a fountain or other decorative feature Yes
1 Decrease Line Flushing Percentage Depends on extent and frequency of current flushing activities No
1 Landscape - Limit landscape irrigation
to specific times Percentage 0-1% Yes
1 Implement or Modify Drought Rate
Structure or Surcharge Percentage 0-10% Municipal Code 13.32.060 Yes 1 Other - Customers must repair leaks,
breaks, and malfunctions in a timely
manner
Percentage 0-1% Uncorrected plumbing or irrigation leaks Yes 1 Landscape - Prohibit certain types of
landscape irrigation Percentage 0-5% Prohibit free-flowing hoses Yes 1 Landscape - Restrict or prohibit runoff
from landscape irrigation Percentage 0-5% Limit excess runoff Yes 1 Other - Require automatic shut of
hoses Percentage 0-5% Yes
1 Reduce System Water Loss Percentage 25-35% Depends on extent and magnitude of current system losses Yes
1 Other - Prohibit vehicle washing
except at facilities using recycled or
recirculating water
Volume 0-5% Yes
1 CII - Restaurants may only serve water
upon request
Percentage 0-1% Yes
1 CII - Lodging establishment must offer
opt out of linen service Volume 0-5% Yes
2 Other Volume N/A Refer to SMC Section 13.32.060 Yes
3 Other Volume N/A Refer to SMC Section 13.32.060 Yes
4 Other Volume N/A Refer to SMC Section 13.32.060 Yes
5 Other Volume N/A Refer to SMC Section 13.32.060 Yes
6 Other Volume N/A Refer to SMC Section 13.32.060 Yes
(E) For each action, an estimate of the extent to which the gap between supplies and demand will be reduced by implementation of the action.
Is the Supplier completing this table using the standard six levels? (yes/no) Submittal Table 8-3 Retail: Demand Reduction Actions
Water Code Section 10632(a)(4)(B) and (E)
Add additional rows as needed
How much is this going to reduce the
shortage gap?
10632(a)(4) Shortage response actions that align with the defined shortage levels and include, at a minimum, all of the following:
(B) Locally appropriate demand reduction actions to adequately respond to shortages.
Volume or Percentage
Drop down
Shortage
Level
Demand Reduction Actions
Drop down list
These are the only categories that will be
accepted by the WUEdata online submittal
tool. Select those that apply.
Additional Explanation or Reference
(OPTIONAL)
NOTES:
Penalty, Charge, or
Other
Enforcement?
For Retail Suppliers Only
Drop Down List
DWR NOTES: Units of measure (AF, CCF, MG) must remain consistent throughout the UWMP as reported in Submittal Table 2-3.
EXHIBIT 1
City Name 60 Day Notice
Drop Down (yes/no)
Notice of Public
Hearing
Drop Down (yes/no)
County Name
Drop Down List
60 Day Notice
Drop Down (yes/no)
Notice of Public
Hearing
Drop Down (yes/no)
CWC 10642 The water supplier is to provide the time and place of the hearing to any city or county within which the supplier provides water.
CWC 10621 (b)Notify at least 60 days prior to the public hearing any city or county within which the supplier provides water that the urban water supplier will be reviewing the plan and considering amendments or changes to the plan.
Submittal Table 10-1 Retail: Notification to Cities and Counties Water Code Section 10621(b) and 10642
Add additional rows as needed
Add additional rows as needed
NOTES:
EXHIBIT 1
ATTACHMENT C: DWR POPULATION TOOL INPUT AND
OUTPUT
PLACEHOLDER
EXHIBIT 1
ATTACHMENT D: 2025 WATER SHORTAGE CONTINGENCY
PLAN
EXHIBIT 1
Public Draft
2025 Water Shortage
Contingency Plan
April 2026
PREPARED BY:
80 Blue Ravine Road, Suite 280
Folsom, CA 95630
(916) 608-2212
EXHIBIT 1
[THIS PAGE LEFT BLANK INTENTIONALLY]
EXHIBIT 1
I
Table of Contents
1 WATER SUPPLY RELIABILITY ANALYSIS ................................................................................ 1 2 ANNUAL WATER SUPPLY AND DEMAND ASSESSMENT PROCEDURES ................................... 2
2.1 Decision Making Process .................................................................................................. 2
2.2 Key Data Inputs ................................................................................................................ 3
2.3 Assessment Methodology ................................................................................................ 4 3 SIX STANDARD WATER SHORTAGE STAGES ......................................................................... 5 4 SHORTAGE RESPONSE ACTIONS .......................................................................................... 6
4.1 Supply Augmentation ....................................................................................................... 6
4.2 Demand Reduction ........................................................................................................... 7
4.3 Operational Changes ...................................................................................................... 11
4.4 Additional Mandatory Restrictions ................................................................................ 12
4.5 Emergency Response Plan ............................................................................................. 12
4.6 Seismic Risk Assessment and Mitigation Plan ................................................................ 12
4.7 Shortage Response Action Effectiveness ....................................................................... 13 5 COMMUNICATION PROTOCOLS ........................................................................................ 13
5.1 Communication for Foreseeable Events ........................................................................ 13
5.2 Communication for Unforeseeable Events .................................................................... 15 6 COMPLIANCE AND ENFORCEMENT .................................................................................... 15
6.1 Stages 1 Enforcement and Penalties .............................................................................. 15
6.2 Stages 2 and Above Enforcement and Penalties ........................................................... 15
6.3 Appeal and Exemption Process ...................................................................................... 16 7 LEGAL AUTHORITIES ......................................................................................................... 16
7.1 City Legal Authorities ..................................................................................................... 16
7.2 Declaration of Water Shortage ...................................................................................... 17
7.3 Proclamation of Local Emergency .................................................................................. 17 8 FINANCIAL CONSEQUENCES OF WSCP ............................................................................... 17
8.1 Financial Impacts and Mitigation Action ........................................................................ 17
8.2 Reporting Cost of Compliance with Excessive Water Use Prohibition During Drought Emergency................................................................................................................................. 18 9 MONITORING AND REPORTING ........................................................................................ 18 10 WATER SHORTAGE CONTINGENCY PLAN REFINEMENT PROCEDURES............................... 18 11 SPECIAL WATER FEATURE DISTINCTION ........................................................................... 19 EXHIBIT 1
II
12 PLAN ADOPTION, SUBMITTAL, AND AVAILABILITY ........................................................... 19 13 LIST OF REFERENCES – TO BE DEVELOPED IN FUTURE SUBMITTAL .................................... 19 EXHIBIT 1
III
List of Tables
Table 2-1: Decision-Making Process and Timeline .................................................................. 3 Table 3-1: Cross-Reference for Standard vs Supplier Shortage Levels (DWR Table 8-1) ............ 6 Table 4-1: Supply Augmentation and Other Actions (DWR Table 8-2) ..................................... 7 Table 4-2: Demand Reduction Actions (DWR Table 8-3) .......................................................... 8 Table 5-1: Communication Protocols per Shortage Stage ...................................................... 14 EXHIBIT 1
1 Public Draft
2025 Water Shortage Contingency Plan
Water shortage contingency planning is a proactive planning process intended to prepare for and respond to potential water supply shortages. Effective planning and preparedness enable water suppliers to maintain reliable service and minimize impacts to customers during periods of supply interruption. Water shortages may result from a variety of factors, including population growth, climate change, drought conditions, regulatory constraints, and natural or human-caused emergencies. A water shortage occurs when available water supplies are insufficient to meet normal customer demands at a given time.
The City of Stockton Municipal Utilities Department (COSMUD) is the City of Stockton’s (City) department responsible for water, wastewater, and stormwater utilities. For purposes of this Water Shortage Contingency Plan (WSCP), the terms “COSMUD” and “City” are used interchangeably to refer to the City of Stockton’s Municipal Utilities Department and its municipal water system.
This plan presents the COSMUD WSCP, which outlines the City’s strategy for preparing for and responding to potential water supply shortages. The WSCP is intended to proactively reduce the risk of severe service disruptions by identifying water shortage levels (or “stages”) and the corresponding response actions that would be implemented during periods of reduced supply.
The WSCP also describes the City’s legal authorities, communication and public outreach procedures, compliance and enforcement measures, and monitoring and reporting requirements associated with water shortage conditions. Stockton Municipal Code (SMC) Chapter 13.28, Water Conservation, and Chapter 13.32, Water Shortage Emergencies, provide the regulatory framework supporting implementation of the WSCP. These complementary code chapters, located under Title 13 of the SMC, have been updated over time and are available at https://ecode360.com/43709814.
The City’s WSCP is intended to be a document that can be updated and amended separately from the 2025 Urban Water Management Plan (UWMP).
1 Water Supply Reliability Analysis
As part of the City’s 2025 UWMP, reliability planning was conducted to evaluate the City’s ability to meet demands. Chapter 7 of the UWMP evaluates the reliability of the City’s water supplies over the 20-year UWMP planning horizon and assesses drought-related risks in accordance with Water Code requirements and the Final 2025 UWMP Guidebook.
The City operates a diversified, conjunctive-use water supply portfolio consisting of surface water, purchased water, and groundwater. Surface water supplies include direct diversions from the San Joaquin River under Water Right Permit No. 21176, treated water purchases from the Stockton East Water District (SEWD), and untreated surface water purchased from the Woodbridge Irrigation District EXHIBIT 1
2 Annual Water Supply and Demand Assessment Procedures 2025 WSCP 2 (WID) and treated at the Delta Water Treatment Plant. Groundwater from municipal wells in the Eastern San Joaquin Groundwater Basin serves as a critical supplemental and drought-response supply.
This integrated approach provides operational flexibility and reduces vulnerability to hydrologic variability, regulatory constraints, and infrastructure outages.
Water supply reliability is evaluated by comparing projected supplies and demands under normal, single-dry, and five-consecutive-dry-year conditions. Under normal conditions, surface water supplies are expected to meet most demands, with groundwater used conjunctively to manage peak demands and provide operational flexibility. During dry and multiple dry years, increased groundwater production offsets reduced surface water availability, consistent with the City’s adopted operational strategy. The assessment assumes conservative estimates of reasonably available supplies from SEWD, WID, the San Joaquin River, and City groundwater wells, consistent with prior UWMPs and contractual obligations.
The Drought Risk Assessment (DRA) evaluates the likelihood and consequences of water shortages over a five-year planning horizon in accordance with 2025 UWMP requirements, considering hydrologic uncertainty, infrastructure reliability, and operational flexibility. Results from the 2021 Water Master Plan indicate that the City’s existing infrastructure and conjunctive use strategy provide strong drought resilience, particularly when supported by active system operations and demand management measures.
The analyses and supporting UWMP tables confirm that the City has sufficient water supplies and system capacity to meet projected demands over the planning horizon under normal, single dry, and multiple dry year conditions, consistent with the conclusions of the 2021 Water Master Plan and prior UWMP cycles.
2 Annual Water Supply and Demand Assessment
Procedures
Section 10632.1 of the CWC requires urban water suppliers to conduct Annual Water Supply and Demand Assessments (Annual Assessment) and submit an Annual Water Shortage Assessment Report (AWSAR) to DWR by July 1 of every year. The CWC requires suppliers to include, as part of their WSCP, specific procedures describing annual steps and timing to complete the Annual Assessment. The Annual Assessment must include a written description of the decision-making process that the City will use each year to determine its water supply reliability, and the key data inputs and assessment methodology used to evaluate the supplier’s water supply reliability for the current year and one dry year.
2.1 Decision Making Process
AWSAR assesses system reliability for the next year using recent water use data before response actions are planned, helping the City anticipate shortages and proactively mitigate impacts for customers. The City will implement the decision-making process and timeline outlined in Table 2-
1. This schedule may be adjusted as needed during implementation.
EXHIBIT 1
2 Annual Water Supply and Demand Assessment Procedures 2025 WSCP 3 Table 2-1: Decision-Making Process and Timeline
TASK TIMELINE
COSMUD Staff will gather key data inputs,
perform the assessment. The assessment will
be finalized based on confirmation of water
supply allocations from Stockton East Water
District (SEWD) and Woodbridge Irrigation
District (WID).
Complete by April 1th
COSMUD Staff will complete the Annual
Assessment and develop the AWSAR based on
the data analysis and information gathered.
Complete by April 15th
COSMUD Staff will present the Annual
Assessment and AWSAR to the COSMUD
Director for review.
Complete by April 30th
COSMUD staff will finalize and resubmit the
Annual Assessment and AWSAR to the
COSMUD Director for Approval.
Complete by May 15th
If the Annual Assessment determines that
available supply will not meet expected
demands, the finalized assessment and
response action recommendations will be
presented to City Council for authorization.
Complete by May 30th
COSMUD Staff may work with regional water
providers and San Joaquin County to declare a
local emergency if needed.
Complete by May 30th
City Council will hold a public hearing to
present the final water shortage assessment
and recommendations. They will decide
whether a water shortage exists and, if
needed, adopt a resolution declaring an
emergency and authorizing response actions.
Complete by June 15th
COSMUD Staff to finalize Annual Assessment
and AWSAR Complete by June 30th
Final approved documents will be submitted
to DWR. Submit by July 1st
2.2 Key Data Inputs
Planned water supplies are evaluated in the Annual Assessment for the current year and one dry year.
The following factors are considered in planning water supplies, as applicable:
1. Hydrological conditions
2. Regulatory conditions
EXHIBIT 1
2 Annual Water Supply and Demand Assessment Procedures 2025 WSCP 4 3. Contractual constraints
4. Surface water and groundwater basin conditions
5. North Stockton and/or South Stockton groundwater well production limitation
6. Infrastructure capacity constraints or changes
7. Capital improvement projects implementation
8. Delta Water Treatment Plant supply availability and/or production issues
9. SEWD supply availability and/or production issues
Planned water supply sources and quantities will be described and should be generally consistent with projections Chapter 6 (Water Supply Characterization) of the City’s most recent UWMP. Significant deviations from projected supplies will be explained.
Unconstrained water demands are customer demands where no water conservation measures are in effect. Planned unconstrained water demands will be inputted into the Annual Assessment for the current year and the following one dry year. In planning for unconstrained water demands, the following factors are considered:
1. Weather conditions
2. Water year type
3. Population changes (due to development projects or other factors)
4. Anticipated new demands (due to land use changes)
5. Pending policy changes with potential impact on demand
6. Infrastructure operations
Planned water demand types and quantities will be described and should be generally consistent with the projections in Chapter 4 (Customer Water Use) of the City’s most recent UWMP. Significant deviations from the projected demands will be explained.
2.3 Assessment Methodology
The City will prepare its Annual Assessment using the following procedures:
• Prepare supply estimates for each water source on an annual basis for the analysis period.
The increments may be revised to monthly or seasonal periods, as needed. This will be accomplished using a spreadsheet with the supply inputs described in Section 2.2. • Update unconstrained customer demand and estimate anticipated actual water use on an annual basis for the analysis period for the analysis period. The increments may be revised to monthly or seasonal periods, as needed. This will be accomplished using a spreadsheet with the unconstrained customer demand inputs described in Section 2.2.
EXHIBIT 1
3 Six Standard Water Shortage Stages 2025 WSCP
5 • Update the infrastructure assessment with monthly estimates of water supply production for the analysis period.
• Identify and assess any region-specific factors that could potentially affect or interrupt supply availability during the analysis period.
• Refine the definition of “dry year” as relevant to dry conditions. • Determine if there is a gap between expected supply and forecasted demand. • Identify and incorporate any applicable constraints (infrastructure, regulatory, etc.). • Create, assess, and recommend water resource management strategies to bridge the gap between estimated supply and expected demand, taking into account the water shortage stages outlined in this WSCP.
• Present the Annual Assessment (and resulting water shortage stage declaration and recommendations, if applicable) to City Council.
If the Annual Assessment shows a need for alternative water shortage response actions beyond those in Section 4, these alternatives will be detailed and submitted in the Annual Assessment as required by CWC 10632.2.
3 Six Standard Water Shortage Stages
CWC Section 10632 (a) (3) requires urban water suppliers to define water shortage levels based on the suppliers’ water supply conditions, including percentage reductions in water supply, changes in groundwater levels, changes in surface elevation or level of subsidence, or other changes in hydrological or other local conditions indicative of the water supply available for use. Suppliers are required to plan for six standard water shortage levels that correspond to progressive ranges up to 10, 20, 30, 40, 50 percent shortages, and greater than 50 percent shortage. The shortage levels should align with the response actions the urban water supplier would implement to meet the severity of the shortages. As shown in Table 3-1, the City uses the standard shortage levels.
EXHIBIT 1
4 Shortage Response Actions 2025 WSCP
6 Table 3-1: Cross-Reference for Standard vs Supplier Shortage Levels (DWR Table 8-1) Check the box if the Supplier uses the
Standard six levels of water shortage.
Proceed to the next table.
Standard
Shortage
Levels
Percent
Shortage
Range
Suppliers
Shortage
Levels
Percent
Shortage
Range
1 Up to 10%
2 Up to 20%
3 Up to 30%
4 Up to 40%
5 Up to 50%
6 >50%
The City’s shortage response actions are addressed in the Stockton Municipal Code (SMC) Chapters
13.28 and 13.32. Chapter 13.28 establishes the City’s baseline and ongoing water conservation requirements, which always apply (standard shortage level 1). Chapter 13.32 is the City’s framework for declaring and responding to water shortage emergencies (standard shortage levels 2-6). A copy of the City’s SMC is available in Attachment H of the City’s 2025 UWMP. 4 Shortage Response Actions
CWC Section 10632(a)(4) requires urban water suppliers to have shortage response actions that align with the defined shortage levels. The City has shortage response actions in place that consist of supply augmentation, demand reduction, operational changes, and an emergency response plan.
The following sections present the individual supply augmentation, estimated demand reduction associated with each response action, additional mandatory restrictions, the City’s emergency response plan, and the City’s seismic risk and mitigation plan.
Actual savings and added supply will likely vary greatly based on external influences, shortage stage level, and general customer understanding of drought severity. It is assumed the savings estimates are not necessarily additive, but when implemented together as a program with all the actions in each respective stage, they are intended and estimated to eliminate each stage’s identified supply to demand shortage gap.
4.1 Supply Augmentation
The City’s water supply strategy relies primarily on surface water from the San Joaquin River, which is treated to meet drinking standards. Groundwater is used as a supplemental source for flexibility and reliability, especially during droughts or emergencies. Rather than maximizing groundwater pumping EXHIBIT 1
4 Shortage Response Actions 2025 WSCP
7 at all times, the City conserves this capacity for critical periods to support drought response and ensure system resilience.
In the event that the City’s water supply is insufficient to meet customer demand, and a water shortage is declared, COSMUD will seek to mitigate water shortages and augment its water supply using the strategies outlined in Table 4-1. Actions include seeking transfers and exchanges with local agencies.
Table 4-1: Supply Augmentation and Other Actions (DWR Table 8-2) Yes Is the Supplier completing this table using the standard six levels? (yes/no) Shortage
Level
Supply Augmentation
Methods and Other
Actions by Water
Supplier
Drop down list
These are the only categories
that will be accepted by the
WUEdata online submittal tool
How much is this going to
reduce the shortage gap?
Additional Explanation or
Reference
(OPTIONAL) Volume or
Percentage
Drop down
Shortage Gap
Reduction
Value
(May be a range)
(AF)
4 Exchanges Volume Up to Shortage
Gap Neighboring agencies
4 Transfers Volume Up to Shortage
Gap
Potentially from
Woodbridge Irrigation
District
5 Exchanges Volume Up to Shortage
Gap Neighboring agencies
5 Transfers Volume Up to Shortage
Gap
Potentially from
Woodbridge Irrigation
District
6 Exchanges Volume Up to Shortage
Gap Neighboring agencies
6 Transfers Volume Up to Shortage
Gap
Potentially from
Woodbridge Irrigation
District
4.2 Demand Reduction
During water shortage conditions, the City plans to implement a series of actions that correspond to each of the standard water shortage levels. Table 4-2 outlines demand reduction measures, their estimated impact on the shortage gap, and compliance actions including penalties, charges, or enforcement.
EXHIBIT 1
4 Shortage Response Actions 2025 WSCP
8 Table 4-2: Demand Reduction Actions (DWR Table 8-3)
Yes Is the Supplier completing this table using the standard six levels? (yes/no) Shortage
Level
Demand
Reduction
Actions
Drop down list
These are the only
categories that will
be accepted by the
WUEdata online
submittal tool. Select
those that apply.
How much is this going
to reduce the shortage
gap?
Additional
Explanation or
Reference
(OPTIONAL)
Penalty,
Charge, or
Other
Enforcement?
For Retail Suppliers
Only
Drop Down List
Volume or
Percentage
Drop down
Shortage
Gap
Reduction
Value
(May be a
range)
(AF)
1 Expand Public
Information
Campaign
Percentage 7-8%
City to encourage
water customers
and users to
implement water
conservation
practices
No
1 Landscape - Other
landscape
restriction or
prohibition
Percentage 0-5%
Prohibit watering
lawns in a manner
that causes runoff,
or within 48 hours
after measurable
precipitation.
Yes
1 Landscape - Other
landscape
restriction or
prohibition
Percentage 0-5%
Prohibit irrigating
ornamental turf on
public street
medians.
Yes
1 Landscape - Limit
landscape irrigation
to specific times
Percentage 0-5%
Prohibit irrigation
between the hours
of 11:00 am to
6:00 pm.
Yes
1 Other - Prohibit use
of potable water
for washing hard
surfaces
Percentage 0-1%
Washing of Street,
driveways,
sidewalks,
buildings
Yes
1 Other Percentage 0-1%
Prohibit any use of
potable water from
a fire hydrant
except by regularly
constituted fire
protection
agencies for fire
suppression
purposes or by the
responsible water
agency.
Yes
EXHIBIT 1
4 Shortage Response Actions 2025 WSCP
9 Shortage
Level
Demand
Reduction
Actions
Drop down list
These are the only
categories that will
be accepted by the
WUEdata online
submittal tool. Select
those that apply.
How much is this going
to reduce the shortage
gap?
Additional
Explanation or
Reference
(OPTIONAL)
Penalty,
Charge, or
Other
Enforcement?
For Retail Suppliers
Only
Drop Down List
Volume or
Percentage
Drop down
Shortage
Gap
Reduction
Value
(May be a
range)
(AF)
1 Water Features -
Restrict water use
for decorative
water features,
such as fountains
Percentage 0-1%
Only recirculated
water can be used
in a fountain or
other decorative
feature
Yes
1 Decrease Line
Flushing Percentage 0-5%
Depends on extent
and frequency of
current flushing
activities
No
1 Implement or
Modify Drought
Rate Structure or
Surcharge
Percentage 0-10% Municipal Code
13.32.060 Yes
1 Other - Customers
must repair leaks,
breaks, and
malfunctions in a
timely manner
Percentage 0-1%
Uncorrected
plumbing or
irrigation leaks
Yes
1 Landscape -
Prohibit certain
types of landscape
irrigation
Percentage 0-5% Prohibit freeflowing hoses Yes
1 Landscape -
Restrict or prohibit
runoff from
landscape irrigation
Percentage 0-5% Limit excess runoff Yes
1 Other - Require
automatic shut of
hoses
Percentage 0-5%
Limit excess and
unnecessary
potable water use
Yes
1 Other Percentage 0-5%
Prohibit use of
potable water for
dust control
purposes except
for public health
and safety
purposes.
Yes
EXHIBIT 1
4 Shortage Response Actions 2025 WSCP
10 Shortage
Level
Demand
Reduction
Actions
Drop down list
These are the only
categories that will
be accepted by the
WUEdata online
submittal tool. Select
those that apply.
How much is this going
to reduce the shortage
gap?
How much is this
going to reduce
the shortage
gap?
Additional
Explanation
or Reference
(OPTIONAL)
Volume or
Percentage
Drop down
Shortage
Gap
Reduction
Value
(May be a
range)
(AF)
1 Other Percentage 0-5%
Prohibit draining or
refilling existing
swimming pools
between June 1st
and October 1st.
Yes
1 Reduce System
Water Loss Percentage 25-35%
Depends on extent
and magnitude of
current system
losses
No
1 Other Percentage 0-7%
Prohibit water loss
through leaks,
breaks, or
malfunctions
within the water
user's plumbing or
distribution system
Yes
1 Other - Prohibit
vehicle washing
except at facilities
using recycled or
recirculating water
Percentage 0-5%
Reduce excess
potable water use
during car washing
activities
Yes
1 CII - Restaurants
may only serve
water upon
request
Percentage 0-1% Reduce water
waste
Yes
1 CII - Lodging
establishment
must offer opt out
of linen service
Volume 0-5%
Reduce excess
water use for
laundry service
Yes
2 Other Volume N/A Refer to SMC
Section 13.32.060 Yes
3 Other Volume N/A Refer to SMC
Section 13.32.060 Yes
4 Other Volume N/A Refer to SMC
Section 13.32.060 Yes
5 Other Volume N/A Refer to SMC
Section 13.32.060 Yes
6 Other Volume N/A Refer to SMC
Section 13.32.060 Yes
EXHIBIT 1
4 Shortage Response Actions 2025 WSCP
11 Chapter 13.28 – Water Conservation of the SMC outlines additional water conservation regulations that are always in place, regardless of the declaration of a water shortage. These include regulations that prohibit clearly defined wasteful and unreasonable water uses, including irrigation runoff, hosing hardscapes, inefficient vehicle washing, and other nonessential uses of potable water, and establishes operational limits on outdoor irrigation and related activities. These requirements apply to all customer classes and are intended to reduce discretionary water use under normal conditions while providing an enforceable baseline that remains in effect during water shortage events.
In response to a water shortage emergency, Chapter 13.32 – Water Shortage Emergencies provides a response guideline, implemented on stage-based mandatory restrictions and enforcement actions.
The stages are consistent with the Six Standard Water Shortage Stages and are implemented as follows:
• Stage 1: Formal declaration of a water shortage emergency; baseline conservation requirements become mandatory and enforceable, building on existing conservation rules to achieve up to 10% demand reduction.
• Stage 2: Additional mandatory restrictions are implemented to further reduce discretionary water use; enforcement and penalties are expanded to achieve up to a 20% demand reduction.
• Stage 3: More restrictive limits on water use are imposed, with increased compliance and enforcement measures to achieve higher demand reductions up to a 30%. • Stage 4: Broad prohibitions on nonessential water uses are implemented, with stringent enforcement to protect remaining supplies, and to achieve up to a 40% demand reduction. • Stage 5: Maximum mandatory restrictions are imposed to preserve water for public health and safety needs, and to achieve up to a 50% demand reduction. • Stage 6: Emergency measures are implemented to maintain minimum system operations, and essential public health and safety uses to achieve over a 50% demand reduction.
4.3 Operational Changes
In response to a water shortage condition, COSMUD may modify system operations on a short-term or long-term basis to maintain water supply reliability and protect public health. Operational changes may include the following:
• Operating a combination of active and standby groundwater wells within the North and South Stockton water service areas to offset reductions in surface water supplies. • Prioritize and expedite repairs to leaks and breaks in the water distribution system, with meter leaks and emergency breaks typically addressed on the same day they are reported and non-emergency service line and main breaks repaired as soon as practical. • During the duration of a water shortage condition, routine water system flushing may be limited and conducted only in areas with identified water quality concerns.
EXHIBIT 1
4 Shortage Response Actions 2025 WSCP
12 • Reducing irrigation on all City-Owned properties within the COSMUD service area.
4.4 Additional Mandatory Restrictions
The mandatory restrictions that will be enforced by the City are outlined in chapters 13.28 and 13.32 of the SMC. This series of restrictions will be implemented at different shortage levels and are summarized in the demand reduction actions in Table 4-2.
4.5 Emergency Response Plan
The City’s latest Water System Emergency Response Plan (ERP) was completed in September 2025 to comply with America’s Water Infrastructure Act (AWIA). This document is required by the AWIA and incorporates findings from the City’s Risk and Resilience Assessment (RRA). The ERP defines procedures for responding to natural disasters, infrastructure failures, and other emergencies that could disrupt water service or threaten public health. The ERP establishes roles and responsibilities for utility staff, identifies emergency response actions to maintain or restore service, and outlines procedures for internal coordination, external agency notification, and public communication.
Consistent with federal requirements, the ERP is treated as a confidential document and is not publicly released.
The City ensures ongoing water service with standby generators, purification equipment, emergency storage, and water trucks. Additionally, water facilities are built to earthquake safety standards and undergo regular inspections.
4.6 Seismic Risk Assessment and Mitigation Plan
California Water Code (CWC) Section 10632.5(a) requires that water suppliers include a seismic risk assessment and mitigation plan as part of their UWMP. The purpose of the seismic risk assessment is to assess and mitigate the vulnerability of the existing facilities in a water system. In lieu of conducting their own seismic risk assessment, it is permitted to address this CWC requirement by submitting a Local Hazard Mitigation Plan (LHMP) if it includes a seismic risk assessment. The City was a part of the team that developed the 2023 San Joaquin County Local Hazard Mitigation Plan (2023 LHMP) development team. The 2023 LHMP was adopted by the San Joaquin County Board of Supervisors and approved by FEMA in April 2023. This LHMP excludes earthquake hazards from consideration because there have been no local earthquakes in the past century; as a result, the 2023 LHMP will not be included in this UWMP.
In March of 2025, the City completed an RRA of its water system to comply with requirements of the AWIA. The RRA evaluated the vulnerability and resilience of COSMUD’s potable water system to natural hazards, including earthquakes. Consistent with AWIA requirements, the assessment considered risks to critical assets such as source waters, wells, treatment and chlorination facilities, storage, pump stations, distribution infrastructure, and supporting operational systems. The assessment evaluated threat likelihood, asset vulnerability, and consequences of failure to identify critical system components and inform capital and operational improvements to enhance system EXHIBIT 1
1 2025 WSCP
13 resilience. Seismic risk mitigation is addressed through ongoing risk and resilience management strategies, including incorporation of seismic resilience considerations into capital improvements and emergency response planning.
AWIA requires RRA’s to be updated and re-certified every five years. The City keeps its RRA as a confidential document.
4.7 Shortage Response Action Effectiveness
Measuring reductions in water use is part of regular procedures, whether during normal or water shortage conditions. The City’s water system is fully metered to keep track of water production and customer water use. Water is supplied to the distribution system based on customer needs, and monthly tracking helps monitor total demand. Through this monitoring, the City can evaluate water system supply and demand levels to determine their alignment with the water shortage response objectives. The potential savings for the shortage response actions are available in Table 4-2. 5 Communication Protocols
Per Section 10632 (a) (5) of the CWC, urban suppliers are required to describe their communication protocols and procedures in the event of a water shortage. In the event of a water shortage, the City must communicate in a timely manner to customers, interested parties, and other relevant local and state agencies.
5.1 Communication for Foreseeable Events
Foreseeable events include water shortage events that can be declared based on the City Annual Assessment procedures described in Section 2. In the presence of a potential water shortage event, The City Council may declare a water shortage emergency according to the procedures outlined in Section 13.32.020 of the SMC. A summary of actions the City could take during a specific water shortage stage is outlined in Table 5-1.
Before a water shortage is declared, the City increases public outreach on the current water supply conditions, the plans for water shortage response, and importance of water efficiency to stretch current supplies. The City’s website includes links to other water conservation announcements and provides a phone number and email to the City Water Conservation Division for any specific questions.
EXHIBIT 1
5 Communication Protocols 2025 WSCP
14 Table 5-1: Communication Protocols per Shortage Stage WSCP Shortage
Stage
Primary Response Actions Communications & Protocols
Stage 1 –
Mandatory
Conservation
Activation of mandatory
conservation requirements
consistent with SMC Chapter
13.28; initial
demand-reduction measures
implemented.
Public notification of Stage 1 declaration via City website, press release, and social media; coordination with COSMUD leadership; customer outreach emphasizing required
conservation practices and reporting of water waste.
Stage 2 –
Moderate
Shortage
Additional mandatory
restrictions implemented
under SMC Chapter 13.32;
expanded enforcement of
conservation measures.
Formal City Council resolution declaring Stage 2; broad public notification through press releases, website updates, utility bill inserts, and social media; coordination with County Office of Emergency Services as needed; direct customer messaging on new restrictions, compliance expectations, and penalties.
Stage 3 –
Significant
Shortage
More restrictive mandatory
limits on water use; increased
enforcement and compliance
actions.
Escalated communications campaign including regular public updates, targeted outreach to high-use customer classes, and coordination with City and County departments;
consistent messaging on restrictions, enforcement, and
potential escalation; reporting to DWR as applicable.
Stage 4 – Severe
Shortage
Broad prohibitions on
nonessential water uses;
stringent enforcement to
protect remaining supplies.
Frequent public updates via multiple platforms (website, media briefings, social media); direct notifications to affected customers; messaging prioritizing public health and safety and explaining emergency measures.
Stage 5 – Critical
Shortage
Maximum mandatory
restrictions imposed; water
use prioritized for essential
public health and safety
purposes.
Emergency-level communications coordinated through
appropriate City staff; frequent press briefings and alerts; direct customer notifications regarding critical restrictions and emergency protocols; coordination with regional and State agencies.
Stage 6 –
Catastrophic
Shortage
Emergency actions to
maintain minimum system
operations and essential uses
only.
Emergency communications to the public through the
appropriate City departments; real-time public alerts and directives; coordination with County, State, and federal agencies; continuous public information focused on health, safety, and system preservation.
EXHIBIT 1
6 Compliance and Enforcement 2025 WSCP
15 5.2 Communication for Unforeseeable Events
Emergency communications protocols are also necessary to address water shortages due to unforeseeable events such as earthquakes, fires, infrastructure failures, civil unrest, and other catastrophic events. The City’s ERP outlines specific communications protocols and procedures to deliver information to appropriate parties in case of an unforeseeable event. 6 Compliance and Enforcement
Stockton Municipal Code Chapters 13.28 (Water Conservation) and 13.32 (Water Shortage Emergencies) establish a progressive enforcement framework that escalates with repeated violations and increasing water shortage severity. Initial violations are typically addressed through written warnings and education to encourage voluntary compliance. Continued or repeat violations may result in administrative citations and penalties, with progressively increasing enforcement applied for subsequent or egregious violations. Upon declaration of a water shortage emergency, particularly Stages 2 through 6, Chapter 13.32 authorizes mandatory restrictions and expanded enforcement authority, including increased penalties and reduced tolerance for non-compliance, to achieve required demand reductions and protect public health and system reliability.
6.1 Stages 1 Enforcement and Penalties
During water shortage Stage 1, the City enforces the requirements of SMC Chapter 13.28. When the City becomes aware of a violation, the City issues a written notice describing the violation and ordering the violation to be corrected, cured, or abated immediately or within a reasonable period. Notices may be served by personal service or first-class mail, by posting at the premises, and a copy is mailed to the person billed for water service; notices may also be served as an addendum to the regular water service bill. Upon a second violation or failure to immediately correct the violation, the City may serve a second notice and impose a surcharge of $100 per day for each day the violation continues, which may be added to the next regular billing.
Violations of Chapter 13.28 are infractions, and each day a violation continues constitutes a separate offense. The Director may also issue cease-and-desist orders and may pursue discontinuance of water service for continued violations, subject to written notice and a hearing prior to termination, and an appeal process to the City Manager as provided in Chapter 13.28
6.2 Stages 2 and Above Enforcement and Penalties
During a declared water shortage emergency of Stage 2 and above, SMC Chapter 13.32 provides the enforcement and penalty framework for Stages 2 through 6. The first billing period after the effective date of the City Council’s declaration is treated as an adjustment period, during which no penalties are imposed for water use in excess of the allocation. Beginning with the second billing period, customers who exceed their established allocation in any billing cycle are subject to an excess use charge, in addition to all other charges, based on a rate schedule adopted by City Council resolution. Excess use charges are not imposed for customers at or below specified minimum consumption thresholds.
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7 Legal Authorities 2025 WSCP
16 In addition to allocation-based charges, Stage 2–6 violations are unlawful infractions. After issuance of one written warning for a violation or prohibited use, the City may install a flow restricting device for at least 48 hours and until the customer pays the applicable removal charge; repeat violations may result in a subsequent flow restrictor period of at least two weeks. Additional violations or tampering with a flow restricting device may lead to water service termination.
6.3 Appeal and Exemption Process
Customers may request allocation adjustments/increases in writing using City forms, which are reviewed by the Water Conservation Officer and decided by the Director. Allocation adjustments may be approved where reasonably necessary based on Code criteria (e.g., additional full-time residents, unusual medical needs, change in property use, demonstrated conservation measures supported by a conservation plan, and certain health care facilities where reductions are maximized without jeopardizing care).
Customers may appeal the Director’s classification, allocation, or allocation-increase determination in writing; appeals may include a Department review and site visit, and sustained appeals may require installation of water-efficient fixtures and/or irrigation systems as a condition of approval. If the customer disagrees with the Director’s decision, the customer may appeal to the City Manager for a final decision; a hearing is scheduled and a written decision is issued within the time frames specified in the SMC, and an appeal fee applies as set by City Council resolution.
For Stage 1 service discontinuance under SMC Chapter 13.28, an affected person may appeal the Director’s decision by filing a written appeal with the City Clerk within 10 days of notice; the City Manager conducts a hearing within 10 days and may affirm, reverse, or modify the decision, which remains in effect during the appeal. The City Manager’s decision is final. 7 Legal Authorities
The next sections explain which legal authorities the City uses to carry out and enforce the shortage response actions listed in the WSCP.
7.1 City Legal Authorities
The City implements this WSCP in accordance with the SMC and City Council actions authorizing water conservation, water shortage emergency declarations, and implementation and enforcement of shortage response actions. The City’s primary local legal authorities for water conservation and water shortage response are the SMC Chapter 13.28 (Water Conservation) and SMC Chapter 13.32 (Water Shortage Emergencies), which the City Council has identified as complementary chapters supporting the WSCP.
The City Council has adopted ordinances amending SMC Chapters 13.28 and 13.32 to update and clarify the City’s water conservation and water shortage emergency provisions. Water shortage stages and associated mandatory measures are implemented through City Council resolutions and EXHIBIT 1
8 Financial Consequences of WSCP 2025 WSCP
17 ordinances, including actions declaring a shortage stage and aligning local requirements with the WSCP framework.
The City provides public-facing information on current conservation requirements and shortage stage status through its Municipal Utilities water conservation webpage and maintains public access to governing documents through City-hosted webpages and repositories, including the City Clerk’s municipal code portal and the City’s WSCP document posting.
7.2 Declaration of Water Shortage
The City shall declare a water shortage emergency, as appropriate, in accordance with CWC Division 1, Chapter 3, Section 350 when it determines that:
• Available water supplies are insufficient to meet normal demands • Conservation is necessary to protect public health, safety, and welfare.
Such a declaration shall be made by City Council action and shall activate the applicable water shortage stage and response actions identified in this WSCP.
7.3 Proclamation of Local Emergency
The City will work closely with other regional water providers and San Joaquin County if there is a need for proclamation of a local emergency. This coordination will take place through the City of Stockton’s Office of Emergency Services (OES), which oversees citywide disaster preparedness and organizes the response of different city departments. If necessary, the City will also activate its Emergency Operations Center (EOC) to manage and support the emergency response efforts. 8 Financial Consequences of WSCP
8.1 Financial Impacts and Mitigation Action
Implementation of the WSCP shortage response actions is anticipated to result in reduced water sales revenue due to lower customer demand during shortage stages and increased operating costs associated with shortage implementation, including staff time for annual assessment/reporting and heightened compliance activities. Under the City’s enforcement framework, financial impacts may also include increased enforcement administration and field activities as shortage stages escalate such as warnings/notices, follow-up, and potential flow-restrictor installation/termination processes.
To help mitigate revenue reductions and recover increased implementation costs during shortage stages, the City’s municipal code provides mechanisms that may be applied during declared shortages, including surcharges for continued violations and Stage 2–6 “excess use charges”, as well as fees/charges associated with prohibited flow-restrictor removal.
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9 Monitoring and Reporting 2025 WSCP
18 8.2 Reporting Cost of Compliance with Excessive Water Use Prohibition During Drought Emergency
During drought emergencies that require mandatory water use reductions, the City incurs costs to comply with excessive water use prohibitions through its previously outlined enforcement procedures and rate mechanisms. Compliance costs include administrative and staff resources associated with identifying excessive water use, issuing written notices and warnings, tracking water use relative to established allocations, billing and collecting excess use charges, and administering appeals and hearings.
Additional compliance costs may be incurred through field and operational activities outlined in this WSCP and authorized by the Municipal Code, including installation and removal of flow-restricting devices and processing of enforcement-related charges. These costs represent the City’s reported cost of compliance with prohibiting excessive water use during drought emergencies. 9 Monitoring and Reporting
COSMUD’s system is metered at its water sources (DWTP, SEWD, and groundwater production wells), and its customers. The City will used the information gathered from these meters to monitor and report WSCP implementation by collecting, tracking, and analyzing customer water-use and supply metrics. These data points are needed to evaluate shortage conditions, measure response effectiveness, and support compliance and enforcement. The City will prepare an Annual Assessment and an AWSAR each year using planned supply and demand inputs, present findings, and recommended actions to City Council. These yearly submissions are an important part of the WSCP’s process for monitoring, determining shortages, and putting different stages into action.
To monitor customer compliance, the City will use data from water meters and billing cycles to ensure customers are following conservation and shortage rules. If a violation occurs, the City will document it by sending written notices or warnings, followed by any necessary additional actions. The City will enforce these requirements using the tools provided in the Municipal Code, such as administering allocation or excess-use charges during Stages 2–6, as well as other authorized enforcement actions.
The City keeps records of its meter readings and enforcement actions to ensure compliance with DWR reporting requirements.
10 Water Shortage Contingency Plan Refinement
Procedures
The City will manage the WSCP as a dynamic tool and will periodically reevaluate and refine procedures and response actions to ensure mitigation strategies remain effective under both foreseeable and unforeseeable shortage conditions. The City will use the findings from the Annual Assessment and lessons learned during WSCP implementation to confirm whether demand-reduction actions are EXHIBIT 1
11 Special Water Feature Distinction 2025 WSCP
19 achieving the intended results and to identify any operational procedures that should be adjusted to better meet the City’s water conservation goals.
If the City identifies a possible change or improvement to the WSCP, it will first assess whether the change is practical to implement, likely to be effective, and in line with both the WSCP’s stage structure and the relevant sections of the municipal code. If the City decides to move forward with a revised WSCP, the updated plan will be submitted for approval following the process outlined in Section 12.
After City Council approval, the revised WSCP will be distributed to San Joaquin County, shared with City customers, and made available to the general public. 11 Special Water Feature Distinction
Special water features, including fountains and other decorative water features, are considered nonessential aesthetic uses of water and are subject to specific conservation limitations. Under SMC Chapter 13.28, it is unlawful to use non-recirculated water in a fountain or other decorative water feature; therefore, decorative water features are only allowable when operated with recirculated water.
12 Plan Adoption, Submittal, and Availability
This WSCP update has been prepared in tandem with the City’s 2025 UWMP. The WSCP (including subsequent updates) shall be adopted in accordance with standard City procedures, which include requirements for public participation (public hearing), and approval by the City Council. Upon adoption, the WSCP will be submitted to DWR and be made available to customers within 30 days. The adopted WSCP will be made publicly available on the City’s website through the Municipal Utilities water planning pages and the City’s public document repository, where adopted water planning documents are posted for public access.
13 List of References – To Be Developed in Future
Submittal
EXHIBIT 1
ATTACHMENT E: WATER SUPPLY REDUNDANCY EVALUATION
EXHIBIT 1
100 Howe Avenue
Suite 110S
Sacramento CA 95825
916.306.2250 phone
530.756.5991 fax
westyost.com
TECHNICAL MEMORANDUM
DATE: January 7, 2026 Project No.: 129-60-20-41
SENT VIA: EMAIL
TO: Travis Small, City of Stockton
FROM: Roberto Vera, PE, RCE #83500
Mika Mar, EIT No. 177465
REVIEWED BY: Elizabeth Drayer, PE, RCE #46872
SUBJECT: Water Supply Redundancy Evaluation
The purpose of this Technical Memorandum (TM) is to summarize findings and recommendations of West Yost’s evaluation of the City of Stockton’s (City) water supply redundancy. This TM is organized as follows:
• Background
• Evaluation Methodology and Criteria
• Water Demands
• Existing Groundwater Supplies
• Supply Capacity Evaluation
• Capital Cost Estimates
• Findings and Recommendations
BACKGROUND
In summer 2024, both of the City’s surface water treatment sources, the Stockton East Water District (SEWD) and the Delta Water Treatment Plant (DWTP), were unexpectedly taken offline at the same time. As a result, the City had to rely entirely on its groundwater facilities for a short period of time.
This event highlighted the need for the City to invest in its groundwater facilities to build additional redundancy to ensure that sufficient water supply can continue to be provided in the event of future surface water supply outages.
Additionally, the City is actively developing a groundwater recharge program, which requires additional wells to recover stored water. Additional investment in groundwater facilities is therefore not just for supply redundancy but also required to be able to maximize the benefit of the recharge program.
This evaluation estimated the number of new groundwater wells and/or well rehabilitations that are required to provide redundant groundwater supply capacity, assuming surface water supplies are not available. The City’s water demands were updated from the values used in its 2021 Water Master Plan (WMP). The evaluation provides planning-level cost estimates to inform rate studies for existing customers and connection fee updates for new development.
EXHIBIT 1
TM – City of Stockton
January 7, 2026
N-C-129-60-20-41-WP-TM-GW Supply Redundancy Eval
EVALUATION METHODOLOGY AND CRITERIA
The purpose of this evaluation was to identify the additional groundwater wells and/or improvements that would be needed to maintain reliable water supply during a complete loss of surface water supplies.
The analysis assumes zero surface water availability, representing a conservative planning scenario consistent with the City’s redundancy and resiliency objectives as well as previous experiences.
The evaluation approach follows the performance and operational criteria established in the 2021 WMP and 2022 Water Master Plan Update (WMPU), updated to reflect current well inventory information provided by City staff in 2025. Two planning scenarios were evaluated:
• Near-term (2030). Used to establish the near-term level of groundwater capacity needed to reliably meet current system demands.
• Buildout (2040). Used to determine the additional improvements required to maintain redundancy under future growth conditions. Buildout demands were consistent with the 2022 WMPU. These demands assume some development changes, further detailed in the Water Demands section.
For each scenario, total firm groundwater capacity was compared to maximum day demand, assuming no surface water supply. Firm capacity was defined as 85 percent of active well capacity, consistent with the City’s planning assumptions. New wells were assumed to provide a firm capacity of approximately 1,500 gallons per minute (gpm) each (assumes a total capacity of 1,765 gpm for each well).
Groundwater well capacities and operational status were updated based on the Well Rehabilitation Status List provided by City staff in March 2025. To optimize improvements and minimize capital cost, wells were identified for potential rehabilitation if they were inactive, less than 40 years old, and located on parcels of at least 0.5 acre, providing sufficient space for the addition of treatment systems and maintenance access.
WATER DEMANDS
For this evaluation, near-term (2030) demands were used to reflect the current pace of development within the City. Several development projects throughout the City have advanced sooner than anticipated in the 2021 WMP, resulting in higher projected system demands sooner than what was assumed in the 2021 WMP. To align groundwater redundancy planning with the accelerated development trends, the near-term demand condition was used in lieu of existing demands. Table 1 summarizes the near-term (2030) demands.
Table 1. Near-Term (2030) Water Demands
Area
Average Day Demand,
mgd(a)
Maximum Day Demand,
mgd(b)
Peak Hour Demand,
mgd(c)
North Stockton 23.8 38.1 59.5
South Stockton(d) 9.8 14.9 26.5
Total 33.6 53.0 86.0
(a) Average day demand based on the 5-year average production from 2015 through 2019, scaled to include a 10 percent demand rebound factor. Refer to Chapter 3 from the 2021 WMP.
(b) Maximum day demand calculated using a peaking factor of 1.6 and 1.7 times the average day demand for North and South Stockton, respectively.
(c) Peak hour demand calculated using a peaking factor of 2.5 and 3.3 times the average day demand for North and South Stockton, respectively.
(d) Demands associated with the Niagara Bottling Facility (Existing Planned and the Additional) are non-peaked constant demands.
EXHIBIT 1
TM – City of Stockton
January 7, 2026
N-C-129-60-20-41-WP-TM-GW Supply Redundancy Eval
Revised buildout (2040) demands, consistent with West Yost’s 2022 evaluation of future development changes1, are summarized in Table 2. These projections reflect updated assumptions for future development. In North Stockton, demands from the Bear Creek South and Origone Subdivision projects were added. In South Stockton, demands from the Food Production Business and Niagara Bottling Facility projects were added, and demands associated with the Mariposa Lakes project were removed to reflect updated service area boundaries.
Table 2. Revised Buildout (2040) Water Demands
Area
Average Day Demand,
mgd(a)
Maximum Day Demand,
mgd(b)
Peak Hour Demand,
mgd(c)
North Stockton(d) 30.5 48.9 76.2
South Stockton(e) 14.1 19.6 33.1
Total 44.6 68.5 109.3
(a) Average day demand based on the 5-year average production plus demands associated with all developments that will be completed by 2040.
(b) Maximum day demand calculated using a peaking factor of 1.6 and 1.7 times the average day demand for North and South Stockton, respectively. Refer to footnote (e) for more details.
(c) Peak hour demand calculated using a peaking factor of 2.5 and 3.3 times the average day demand for North and South Stockton, respectively.
(d) See "Bear Creek South Development Water System Evaluation" Technical Memorandum (West Yost Associates, 03/03/2022), refer to Table 2. Origone Subdivision demand projected based on land use information from the 2011 Origone Ranch Specific Plan and water use factors from the City's 2021 WMP. Refer to footnote (e) for more details. (e) See "Food Production Business Project Impact Evaluation to the South Stockton Water System" Technical Memorandum (West Yost Associates, 07/01/2022) Table 2. See "Additional Niagara Bottling Facility Demand Impact Evaluation to the South Stockton Water System" Technical Memorandum (West Yost Associates, 07/22/2022) Table 2. Demands associated with the Niagara Bottling Facility (Existing Planned and the Additional) are non-peaked constant demands. Food production business demand is constant and nonpeaked. Demands exclude Mariposa Lakes.
The two demand conditions summarized in Tables 1 and 2 are the basis for the subsequent supply capacity evaluation, which quantifies the number of new or rehabilitated wells required to provide firm groundwater capacity equivalent to near-term (2030) and buildout (2040) maximum day demands with no surface water supplies.
EXISTING GROUNDWATER SUPPLIES
A summary of current groundwater well facilities, including status, capacity, and rehabilitation potential, is provided in Table 3. Groundwater facility information was updated based on the Well Rehabilitation Status List provided by City staff via email on March 18, 2025. The list included current well capacities, operational status, and site characteristics such as parcel size and well age.
Wells were reviewed to identify opportunities for rehabilitation or replacement to improve system reliability and cost efficiency. Wells were considered suitable for rehabilitation if they were inactive, less than 40 years old, and located on parcels of at least 0.5 acre, providing sufficient space for the addition of treatment systems and maintenance access.
Based on discussions with City staff, Wells 25 and 30 in North Stockton were identified as the most suitable sites for near-term improvement. Well 25 is proposed for on-site replacement due to existing mechanical 1 West Yost. December 2022. Water System Impact Evaluation of Future (2040) Development Changes.
Technical Memorandum.
EXHIBIT 1
TM – City of Stockton
January 7, 2026
N-C-129-60-20-41-WP-TM-GW Supply Redundancy Eval
issues, while Well 30 is a candidate for treatment installation to address 1,2,3-TCP. As a result, only Well 30 was considered a viable for rehabilitation. Improvements to Well 25 would essentially result in a new well facility.
Overall, the existing active groundwater capacity has decreased slightly since completion of the 2021 WMP. In North Stockton, the total active well capacity is now approximately 18,300 gpm (26 mgd), compared to about 19,500 gpm (28 mgd) reported in the 2021 WMP. This reduction is primarily attributed to several wells that have since become inactive or require mechanical repair or treatment, including Wells 24, 25, and 30. In South Stockton, the total active capacity is approximately 6,000 gpm (8.6 mgd), which is similar to the 5,900 gpm (8.5 mgd) reported in the 2021 WMP.
Table 3. Summary of Well Facilities(a)
Well
Number
Parcel
Size, ac(b)
Well
Status
Well Age,
years Notes
2025
Well
Pump
Capacity,
gpm
Firm
Active
Well
Capacity,
gpm(c)
Rehabilitation
or
Replacement
Candidate(d)
North Stockton
3R 1.84 Active – 2,000 1,700 –
10R 6.84 Active – 3,200 2,720 –
15 0.11 Standby 50 Manganese Tier 2
violation 1,805 – Unlikely
18 2.63 Active 69 800 680 –
19 0.17 Active 47 1,780 1,513 –
20 0.18 Inactive 47
Iron and
manganese Tier 2
violation
1,800 – Unlikely
21 5 Active 47 1,800 1,530 –
24 0.28 Inactive 43 Bad motor 430 – Unlikely
25 5.36 Inactive 41
Mechanical issues
(current well pumps
mud)
1,600 –
Potential
Replacement
26 0.19 Inactive 38 Mechanical issues 1,970 – Unlikely
27 0.24 Active 40 2,200 1,870 –
28 0.14 Standby 28 1,2,3-TCP 1,600 – Unlikely
29 6.36 Active 25 2,500 2,125 –
30 7.6 Standby 22 1,2,3-TCP 2,200 –
Potential
Treatment
31 0.18 Active 21 2,000 1,700 –
32 0.57 Active 21 2,000 1,700 –
Existing Groundwater Well Capacity (Active) 18,280 15,538 Existing Groundwater Well Capacity (Inactive or Standby) 11,405 9,694 Existing Groundwater Well Capacity
(Inactive or Standby and Candidate for Rehabilitation) 2,200 1,870 Well 30 is the
only
recommended
candidate for
rehabilitation
EXHIBIT 1
TM – City of Stockton
January 7, 2026
N-C-129-60-20-41-WP-TM-GW Supply Redundancy Eval
Table 3. Summary of Well Facilities(a)
Well
Number
Parcel
Size, ac(b)
Well
Status
Well Age,
years Notes
2025
Well
Pump
Capacity,
gpm
Firm
Active
Well
Capacity,
gpm(c)
Rehabilitation
or
Replacement
Candidate(d)
South Stockton
SSS #1 0.14 Inactive 41 Iron 1,000 – Unlikely
SSS #2 0.15 Standby 72 1,2,3-TCP 1,295 – Unlikely
SSS #3 0.14 Active 36 PFOA/PFAS 2,000 1,700 –
SSS #8 5.69 Active 25 PFOA/PFAS 1,500 1,275 –
SSS #9 0.22 Active 21 2,500 2,125 –
Existing Groundwater Well Capacity (Active) 6,000 5,100 Existing Groundwater Well Capacity (Inactive or Standby) 2,295 1,951 Existing Groundwater Well Capacity
(Inactive or Standby and Candidate for Rehabilitation) 0 0 (a) Status and pump capacities were updated based on ‘Well Rehabilitation List v2025.xlsx’, provided by the City in March 2025. (b) Parcel sizes assumed based on County of San Joaquin District Viewer, accessed on July 31, 2025. (c) Consistent with assumptions in the WMP, firm active well capacity is 85 percent of the active well capacity. (d) Wells selected for rehabilitation based on age (less than 40 years old) and parcel size (at least 0.5 acres).
SUPPLY CAPACITY EVALUATION
The 2021 WMP evaluated total supply capacity based on a combination of surface water and groundwater sources. For this evaluation, only groundwater supplies were considered to determine the additional capacity needed to meet system demands during a complete loss of surface water supplies. The analysis was performed for both the near-term (2030) and buildout (2040) demand conditions to identify the well rehabilitations and new wells required to maintain reliable service.
Consistent with City planning criteria, firm groundwater capacity was assumed to be 85 percent of total active well capacity. For inactive or standby wells, firm capacity was also assumed to be 85 percent of their rated capacity, if reactivated. New wells were assumed to have a design capacity of 1,800 gallons per minute (gpm) and a firm capacity of 1,500 gpm.
These assumptions were applied to both demand scenarios to estimate total firm groundwater capacity and to identify capacity deficits under each condition. The results are summarized in the following sections.
Near-Term Water Supply Redundancy Evaluation
Table 4 summarizes the results of City’s ability to meet maximum day demands, with current groundwater facilities under near-term demand conditions. As shown, the existing firm well capacity is approximately
22.4 mgd in North Stockton and 7.3 mgd in South Stockton, compared to maximum day demands of
38.1 mgd and 14.9 mgd, respectively. This results in capacity deficits of 15.7 mgd in North Stockton and
7.6 mgd in South Stockton.
EXHIBIT 1
TM – City of Stockton
January 7, 2026
N-C-129-60-20-41-WP-TM-GW Supply Redundancy Eval
To address these deficits, the following improvements are recommended:
• North Stockton
— Rehabilitate Well 30 with treatment to restore capacity. — Construct seven new wells to provide additional groundwater supply capacity. • South Stockton
— Construct four new wells, likely with treatment.
These improvements would increase firm capacity by approximately 17.8 mgd in North Stockton and
8.6 mgd in South Stockton, resulting in surpluses of 2.1 mgd and 1.1 mgd, respectively.
Table 4. Near-Term Supply Capacity Evaluation
Component North Stockton, mgd South Stockton, mgd
Existing Firm Surface Water
Treatment Plant Capacity 0.0 0.0
Existing Firm Well Capacity 22.4 7.3
Near-Term (2030)
Maximum Day Demand 38.1 14.9
Supply Surplus (Deficit) (15.7) (7.6)
Additional Firm Capacity from
Recommended Rehabilitated Wells
2.7 (1 well, Well 30)
No rehabilitation candidates
Additional Firm Capacity from
Recommended New Wells
15.1 (7 wells)
8.6 (4 wells with treatment)
Revised Supply Surplus (Deficit) 2.1 1.1
Buildout Water Supply Redundancy Evaluation
Table 5 summarizes the results of the City’s ability to meet maximum day demands under buildout (2040) conditions using groundwater-only. The analysis excludes demands associated with the Mariposa Lakes development, which is outside the City’s service area. As shown in the table, the firm groundwater capacity remains approximately 22.4 mgd in North Stockton and 7.3 mgd in South Stockton, while maximum day demands increase to 48.9 mgd and 19.6 mgd, respectively. This results in deficits of
26.5 mgd in North Stockton and 12.3 mgd in South Stockton.
To address these deficits, the following additional improvements are recommended, assuming the existing-condition improvements are completed:
• North Stockton
— Construct five additional new wells to provide increased capacity for buildout demands. • South Stockton
— Construct two additional new wells with treatment to provide additional firm capacity.
These improvements would increase firm capacity by approximately 25.9 mgd in North Stockton and
13.0 mgd in South Stockton, resulting in surpluses of 2.1 mgd and 0.7 mgd, respectively.
EXHIBIT 1
TM – City of Stockton
January 7, 2026