RES 2026043 - Laserfiche WebLink

Section 7 2025 Urban Water Management Plan Water Supply Reliability Assessment City of Pleasanton Public Draft | May 2026 7-1 EKI Environment & Water, Inc. 7 WATER SUPPLY RELIABILITY ASSESSMENT This section describes the City’s water service reliability under various hydrologic conditions, including a severe drought for the next five years. The City’s existing and planned water management tools for increasing water supply reliability are also addressed. Responses to actual water shortage conditions are detailed in Section 8 of this plan. The reliability of the City’s potable water supply is largely dependent upon its water supply from Zone 7 and Zone 7’s water supply reliability policy. On October 17, 2012, the Zone 7 Board approved a revised Water Supply Reliability Policy (Resolution No. 13-4230), which adopts the following level of service goals to guide the management of Zone 7’s treated water (also referred to as M&I) supplies and its Capital Improvement Program (CIP): • Goal 1: Zone 7 will meet its treated water customers’ water supply needs, in accordance with Zone 7’s most current Contracts for M&I Water Supply, including existing and projected demands as specified in Zone 7’s most recent UWMP, during normal, average, and drought conditions, as follows: — At least 85% of M&I water demands 99% of the time — 100% of M&I water demands 90% of the time • Goal 2: Provide sufficient treated water production capacity and infrastructure to meet at least 80% of the maximum month M&I contractual demands should any one of Zone 7’s major supply, production, or transmission facilities experience an extended unplanned outage of at least one week. To evaluate water service reliability, Zone 7 developed an advanced water supply management model for the 2022 WSE Update, which superseded the previous spreadsheet-based model developed for the 2019 WSE Update. The model is implemented in RiverWare and simulates Zone 7’s updated demand, integrated supply, storage, conveyance, treatment, and groundwater operations on a monthly time step, allowing the analysis to reflect seasonal patterns, operational constraints, water rights, and year-to-year carryover storage behavior. Hydrologic uncertainty is represented using the Index Sequential Method, which generates multiple hydrologic “traces” by shifting through the historical record so that wet, average, and dry sequences (including multi-year droughts) are preserved while providing many plausible future sequences for evaluation. The historical hydrologic inputs (e.g., SWP availability and local hydrology proxies) are adjusted to account for climate change impacts and aging infrastructure in the SWP. Each trace is simulated across the full planning horizon (2025-2050). In this modeling effort, Zone 7 defines operating rules that represent how the system is managed as different supply sources come online or go offline—this includes priorities for use of SWP deliveries, local surface water, groundwater pumping, storage drawdown and refill targets, and use of banking and transfers—along with key physical constraints (e.g., conveyance capacities, treatment limits, pumping limits, and storage capacities). For this 2025  CWC §10620 (f) An urban water supplier shall describe in the plan water management tools and options used by that entity that will maximize resources and minimize the need to import water from other regions.  CWC §10630.5 Each plan shall include a simple lay description of how much water the agency has on a reliable basis, how much it needs for the foreseeable future, what the agency’s strategy is for meeting its water needs, the challenges facing the agency, and any other information necessary to provide a general understanding of the agency’s plan.