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City of Pleasanton 4.0 Water Agency Background Final Water Supply Assessment Stoneridge Drive Specific Plan Amendment and Staples Ranch Project Semitropic Water Storage District and Cawelo Water Storage District to sustain demands throughout Zone 7's service area through the worst credible drought.13 As part of the Plan, Zone 7 established a safe yield for annual groundwater extractions by the Tri- Valley retailers. The safe yield or long-term sustainable yield is defined as the average amount of water that can be pumped annually from the Main Groundwater Basin and replenished by natural recharge. Safe yield is 13,400 AFA for the cities of Pleasanton and Livermore, DSRSD and other local pumpers, which is about 6 percent of the total estimated groundwater storage and is based on over a century of hydrologic records and projections of future recharge conditions.14 5.3.4.3. Surface Water Supplies 5.3.4.3.1. State Water Project Supplies In November 1961, Zone 7 entered into a 75-year agreement with DWR and in 1962, received its first delivery from the SWP. Zone 7 was the first wholesaler to receive SWP water. SWP water originates within the Feather River watershed above Lake Oroville, and flows via the Sacramento- San Joaquin Delta to the California and SBA's into Zone 7's two current water treatment facilities, the Del Valle Water Treatment Plant and the Patterson Pass Water Treatment Plant. Imported surface water forms the majority of Zone 7's water supply portfolio; this equates to about 75 percent of the total treated water supplied to its four retail water customers. SWP water meets all Municipal and Industrial (M&I) demands, agricultural and other raw water demands, and is also used to artificially recharge the groundwater basin. Zone 7 reached its initial SWP contract maximum of 46,000 AFY in 1997. DWR and Zone 7 developed a delivery schedule commonly referred to as Table A Amount Schedule. Since then Zone 7 has obtained additional SWP allocations through water transfers with other SWP wholesalers, and now has long-term SWP contracts for delivery of up to 80,619 AFA. Table 5-2 presents sources and quantities along with contract terms. For long-term water supply planning purposes, due to annual hydrologic conditions, requests by other SWP contractors, facility limits within SWP facilities, along with environmental/ State regulatory requirements, DWR will not be able to supply Zone 7's full Table A Amount of 80,619 AF in any given year. To compound the situation, as Metropolitan Water District in Southern California takes more of its SWP allotment each year, the annual SWP yield to other contractors is likely to decline. Furthermore, the average yield of the SWP will continue to decline as demands on the system continues to increase from 3.8 to 4.1 million acre-feet per year. Zone 7 staff reviewed DWR's State Water Project Delivery Reliability Report (December 2002) that presented the results of the CALSIM II modeling for SWP systems; DWR's operational studies indicate an average future yield of just less than 76 percent of Zone 7's full allocation, or 60,900 AFA based on the current SWP Table A amount of 80,619 AFA.75 13 2005 Zone 7 Water Agency, Urban Water Management Plan, page 19. 14 2005 Zone 7 Water Agency Urban Water Management Plan, page 20. 15 Zone 7 Water Agency, Sustainable Water Supply Report, April 2007 page 3. PiProjects - WP Onty141162.01 Staples Ranch WSAtFinallFinal WSA.doc 5-13