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THE CITY OF <br />Chapter 7 <br />Water Service Reliability and Drought Risk Assessment PLEASANTON, <br />7.1.2 Year Type Characterization <br />The City's potable water supply reliability and vulnerability are directly related to seasonal and climatic <br />shortages that impact Zone 7's water supplies. The quantity available from different supply sources varies <br />annually depending on hydrologic conditions. Consequently, Zone 7 reviewed historical data and developed <br />a projected yield for each water supply source (including the Main Basin) under three conditions: (1) normal <br />water year, (2) single dry year, and (3) five -consecutive -year drought. Each condition is defined as follows: <br />• Normal Water Year: The year in the historical sequence most closely representing average <br />runoff or allocation levels and patterns. <br />• Single Dry Year: The year in the historical sequence with the lowest annual runoff or allocation. <br />• Five -Consecutive -Year Drought: The driest five-year historical sequence. <br />Zone 7's water supply reliability is used to represent the City's available supplies during the above <br />hydrologic conditions. The projected yield of Zone 7's water sources under these three scenarios, as <br />detailed in Zone 7's 2020 UWMP, are summarized below. <br />In its 2020 UWMP, Zone 7 provides a basis of water year data table (DWR Table 7-1) for each of its water <br />supply sources. For simplicity, this plan leaves DWR Table 7-1 blank and summarizes Zone 7's base year <br />information and water supply availability in Table 7-2 and Table 7-3, respectively. <br />Table 7-1. Basis of Water Year Data (Reliability Assessment) (DWR Table 7-1 Retail) <br />Quantification of available supplies is not <br />0 compatible with this table and is provided <br />elsewhere in the UWMP. <br />Location: Tables 7-2 and 7-3 <br />Table 7-2. Basis of Water Year Data for Zone 7 Supplies <br />Water Source <br />Year <br />Prought <br />SWP—TableA <br />1965 <br />2014 <br />1987 <br />1988 <br />1989 <br />1990 <br />1991 <br />SWP — Carryover <br />1965 <br />2014 <br />1987 <br />1988 <br />1989 <br />1990 <br />1991 <br />Water Transfers <br />1965 <br />2014 <br />1987 <br />1988 <br />1989 <br />1990 <br />1991 <br />Arroyo Valle <br />1919 <br />1977 <br />1987 <br />1988 <br />1989 <br />1990 <br />1991 <br />Sites Reservoir <br />1965 <br />2014 <br />1987 <br />1988 <br />1989 <br />1990 <br />1991 <br />BARDP and/or Potable Reuse <br />1965 <br />2014 <br />1987 <br />1988 <br />1989 <br />1990 <br />1991 <br />From Storage <br />Main Basin <br />1965 <br />2014 <br />1987 <br />1988 <br />1989 <br />1990 <br />1991 <br />Semitropic <br />1965 <br />2014 <br />1987 <br />1988 <br />1989 <br />1990 <br />1991 <br />Cawelo <br />1965 <br />2014 <br />1987 <br />1988 <br />1989 <br />1990 <br />1991 <br />Chain of Lakes <br />1965 <br />2014 <br />1987 <br />1988 <br />1989 <br />1990 <br />1991 <br />WEST YOST <br />7-7 <br />Source: Zone 7 2020 UWMP, Table 7-1 through Table 7-9 <br />City of Pleasanton <br />2020 Urban Water Management Plan <br />May 2021 <br />