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4.Environmental Analysis r The model considers the primary factors affecting groundwater recharge including land use (i.e., agricultural areas, urban areas and undeveloped areas), rainfall distribution, soil properties, and amounts of applied water for irrigation. Based on these factors,the model estimates the average infiltration in agricultural areas at approximately I 1 inches of water per year and in undeveloped areas is estimated to be approximately 1 inch. Infiltration of natural excess rainfall in the undeveloped areas is very limited in comparison to the agricultural sources. Background ` information reviewed for this EIR included project site-specific annual agricultural demand records from irrigation wells,domestic wells, and canal turnouts on the project site for the years 1997 to 2003.These records included a seven-year average pumping rate of 95 acre-feet for the Barnes property irrigation well and a seven-year average pumping rate of 474 acre-feet for the A&L Property irrigation well. Canal turnouts at the Barnes property, A&L property, and Costa Ranch totaled 480 acre-feet for the year 2003. Domestic water with partial agricultural use totaled 2.5 acre-feet. This data indicates that in a single year, in this case,2003, an average of 1,051 acre- feet of irrigation water was applied to the site. This equals approximately 18 inches of water per year available for infiltration, recharge, and evapotranspiration(water released to the atmosphere by evaporation from soil and plant surfaces). This figure is based on a single year and the quantity of applied irrigation water would vary depending on annual climate and crop type. 61 Groundwater Budget A groundwater budget is a method of quantitatively accounting for water movement in a hydrologic system. DWR's Bulletin 160-93,estimated usable storage capacity for the San Joaquin River Region to be approximately 24 million acre feet(maf) (DWR 1994 in SJRG, 2003).There have been numerous attempts to estimate what is sometimes referred to as the safe yields of the San Joaquin River Region. The most recent estimate for annual safe yield, or the amount of water that the aquifer can supply, is approximately 3.3 maf of annual yield(DWR 1994 in SJRG, 2003). DWR estimates that municipal and irrigation uses extract 3.5 maf of water per year in the San Joaquin River Region. The estimated extraction volume of 3.5 maf of water exceeds estimated annual safe yield by approximately 200,000 acre-feet(AF). Exceedence of the safe annual yield can lead to overdraft of a groundwater basin. All of the sub-basins within the San Joaquin River Region have experienced some overdraft(DWR, 1994). The network of water supply aqueducts in the Central Valley is sufficient to provide for over one- half of the water needed for irrigation in years of average or above-average rainfall. In dry years when rainfall is below normal,reliance on ground-water supplies is greater. During times of ` severe drought, groundwater could be removed from the regional aquifers in excess of recharge, as they were during the 1976-1977 drought(USGS, 2003).Although gains have been achieved by importing surface water from areas of surplus,projected water needs in the San Joaquin Valley may require temporary withdrawal of ground water in excess of recharge in the future. The DWR estimates that by 2010,demand for water in the San Joaquin Valley,exclusive of the Tulare Basin,would be 8 percent greater than the groundwater demand in 1980. Without ° The safe yield of a groundwater basin is the amount of water that can be withdrawn from it on a yearly basis V without producing an undesirable result.Undesired results include the depletion of groundwater reserves,the intrusion of poor quality water,depletion of stream Flow,and land subsidence(Freeze and Cherry, 1979). RMC Pacific Vemalis Quany Mining and Reclamation Project 4.8-14 ESA/203015 Draft Environmental Impact Report May 2006