10 ATTACHMENTS - Laserfiche WebLink

COMPONENTS OF THE LIVERMORE VALLEY'S SUSTAINABLE WATER SUPPLY State Water Project (SWP) future average delivery In 1962, Zone 7 became the first State Water Project Contractor to take water deliveries. Since 1962 Zone 7 has increased our share of water and currently has along-term contract with the SWP for delivery of 80,619 acre-feet of water a year. This "Table A Amount" was previously referred to as "Maximum Annual Entitlement." However, the SWP with its present configuration and lower demands can only deliver about 82% of its current requested amounts and this quantity will decrease as the demands by all SWP contractors increase. DWR's early operation studies using the older DWRSIM (computer model) under the Monterey Agreement indicate an average future (2020) yield of 75.57% (60,900 acre-feet). "The State Water Project Delivery Reliability Report", December 2002, which uses CALSIM II model data indicates an average yield of 75-76% (74.59% for Study 2021A, 75.73% for Study 2021B). The DWR 2005 Reliability Report, indicates an average yield of 77 percent. Zone 7 staff has reviewed this report and confirms that an estimate of 75.57% as the average future yield is still generally valid. Lake Del Valle future average yield is water developed by the Zone under its water rights permit for the Arroyo Del Valle. This water is captured and made available in the Del Valle Reservoir through operating agreements with the State Department of Water Resources. The 30- year historic yield to Zone 7 is about 8,000 acre-feet. The future and long-term yield (2020) is calculated at 9,300 acre-feet based on modeling of historic runoff data and future Zone 7 winter season demands. There have been changes in the recharge characteristics of the Arroyo Valle and changes in our joint use of local water with ACWD. Zone 7 staff will have to conduct new modeling studies to assess the impacts of changes in Arroyo Valle recharge characteristics and changes in our joint water operations with ACWD. Byron Bethany Irrigation District (BBID) This water is purchased from BBID and imported via the South Bay Aqueduct for use in our service area. Zone 7 entered into along-term (15 year renewable every 5 years) contract with BBID for up to 5,000 acre-feet annually. In 1999 the Zone 7 Board certified the EIR for this water supply. Although we could take up to 5,000 acre- feet per year and have taken up to about 4,000 acre-feet per year, we are using 2,000 acre-feet as a conservative estimate of the sustainable supply from this source. Subtotal: Zone 7 component of Valleywide sustainable water suppl~This is the sum of the three sources described above. Zone 7 Water Agency, over our 50 year history has developed over 72 thousand acre-feet of sustainable water supply for the Livermore-Amador Valley and is responsible for the management of over 80 percent of the valleywide supply. Safe Groundwater Yield From Main Basin is defined as the amount of water that can annually be pumped from the groundwater basin and replenished by average annual natural recharge. More water can be and is pumped from the main basin each year as long as Zone 7 artificially recharges the basin with additional water from our other sources. The long-term baseline safe yield is based on natural recharge and over a century of hydrologic records and projections of future recharge conditions. The safe yield in the main groundwater basin is 13,400 acre-feet annually. From this baseline safe yield, the Valley's major water retailers are permitted to pump a combined 7,200 acre-feet annually. This amount, referred to as the Groundwater Pumping