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BACKGROUND: Following the most recent multi-year drought (1987-92), the Zone 7 Board requested an annual report of the Sustainable Water Supply. Typically each April since 1992, the Zone staff has reviewed the Livermore Valley's long-term "sustainable water supply" and has prepared a summary report. Since the last drought, Zone 7 has purchased additional long-term water supplies from the State Water Project (SWP). Zone 7's maximum annual contract amount, now referred to as our "Table A Contract Amount", has increased from 46,000 to 80,619 acre-feet. (Note that the Table A contract amount was previously referred to as SWP maximum annual "entitlement" or MAE, but due to potential confusion over the use of the word "entitlement", the SWP will no longer use that term.) With these new purchases, Zone 7 has sufficient sustainable water supplies to provide for all potable water demands through buildout and for all currently contracted non-potable (untreated) water demands. The scope of the analysis has expanded over the years and has adapted to incorporate changes in State Water Project operations and new Zone 7 facilities. In 2002, staff incorporated multi-year operations modeling and salt balance calculation into our review. This modeling includes an evaluation of all past hydrologic events from the past 80 years and includes the worst single-year drought of record (1977) and the two worst multi-year droughts of record (1928-34 and 1987- 92). In 2004, staff expanded the multi-year modeling to incorporate the new version of the DWR CALSIM II that included coordinated operation of State and Federal operations and included the Environmental Water Account. In 2004 the CALSIMII 2021B version was considered the most effective study for future conditions. In September 2005, Zone 7 updated the Urban Water Management Plan and based it on the most recent data available at that time. DWR had not finalized the "SWP Delivery Reliability Report" and only a draft report (June 2005) was available. At that time Zone 7 utilized "Study Number 7" in the draft report as the most appropriate data source for future SWP delivery. In August 2005, Zone 7 prepared an updated Sustainable Water Supply report to document the data used in the 2005 UWMP update. In August 2005, Zone 7 had sufficient storage to maintain a sustainable water supply and meet full deliveries through about 2014 without pumping the local groundwater basin storage below historic lows. In 2006 Zone 7 purchased additional groundwater storage capacity in the Cawelo Water Storage District Banking Program and made the first deliveries of water into storage. With the recent addition of Cawelo Water Storage District, Zone has sustainable water supplies to meet all potable and non-potable demands through buildout. In June 2006 DWR published "The State Water Project Delivery Reliability Report 2006" (http://baydeltaoffice.water.ca.gov/SWPRe105 final.pdf)IrithesummerOf2UU6, Zone 7 approved the purchase of storage and pump back capacity in Cawelo Water Storage District and transferred 10,000 acre-feet of water to Cawelo for long term drought reliability. This updated analysis includes the most recent studies from the State reliability report and includes the Cawelo Banking program. 2