2007-12-19_REVISION - M1988112 (12)

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www.wrcc.dri.edu), with July and August receiving the greatest monthly precipitation, and January and February receiving the least. The outflow components of the pond water balance model included pond outflow to irrigation and lake evaporation. The irrigation ponds will be lined using a synthetic geomembrane material (HDPE or similar) and, as a result, seepage losses from the ponds are negligible and are substantially less than the estimated annual infiltration rate of natural precipitation. Estimates of irrigation outflows from the ponds were based on crop consumptive use data as reported in the Supplemental Water Supply Plan (SWSP) submitted to the State Engineers Office for an alfalfa crop assuming two center pivots would irrigate a total combined area of 281 acres (Lytle Water Solutions, 2007). As reported in the SWSP, consumptive water use for alfalfa is 17.4 inches annually, which was distributed throughout the irrigation season as shown in Figure G.2-2. Total losses from the center pivots is estimated to be 20 percent (i.e., spray head evaporation [5%] and deep percolation [15%]) such that the annual flow through the center pivots for irrigation will be 21.7 inches per acre. There will be no increase in historical consumptive water use under this irrigation program. Irrigation demand is seasonally distributed. Estimates of evaporation from the ponds were based on pan evaporation data from the Western Regional Climate Center (WRCC; www.wrcc.dri.edu) for Alamosa, Colorado. Pond evaporation is effectively equal to lake evaporation, with lake evaporation assigned a value equal to 70 percent of measured pan evaporation. Evaporation from the pond surfaces was set to an average annual value of 37.7 inches with seasonal distribution occurring over the months from April through October. The monthly pan evaporation is also shown in Figure G.2-2. Results of water balance modeling for the irrigation ponds indicate that the average required storage volume for the period from November through March is 169 acre- feet (Figure G.2-3). Average annual combined flow from the West Pit and alluvial aquifer ground water wells is about 240 gallons per minute, with seasonal peak flows occurring in late spring/early summer, and low flow during the winter months. Battle Mountain Resources, Inc. 24 P:\Pmjmts\212-Ne ont(SenLws)\S=LWs\Pemrit Amedment- WeA Pit Memgen AV5 Report @PDFs\Tezt\PelmitAmendmem_v5c.&c December 2007