2006-07-20_REVISION - M1988112 - Laserfiche WebLink

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G.2.1 Pond Sizing -Water Balance Calculations The primazy design objective for the irrigation pond is to ensure adequate storage for pit and interceptor well waters during the non-irrigation period. Water balance calculations were made to provide an estimate of storage requirements for the pond. The water balance calculations were made using augmentation flow records, monthly Dischazge Monitoring Reports, operational logs, and crop irrigation requirements. The analyses include the seasonally variable West Pit ground water well (BF-SR, BF- 4, and BF-3) and alluvial capture well (M-32 and M-33) flows (Figure G.2-1). Inflow sources in the water balance model included the Wes[ Pit ground water, the alluvial ground water, and direct precipitation. Flows from the ground water wells in the West Pit and alluvial aquifer were calculated using available historical pumping records. The pumping records for the analyses cover the period from 2002 through 2005. The average annual flow from the wells during this period was 390 acre-feet. Precipitation inputs for the water balance model assumed that inflow occurred as direct precipitation to the irrigation pond and that no runoff from upland areas will report to the pond. Precipitation was assumed to average 15 inches per yeaz, with July and August receiving the greatest monthly precipitation, and Januazy and February receiving the least. The outflow components of the pond water balance model included pond outflow to irrigation, evaporation, and seepage.. Estimates of irrigation outflows from the pond were based on crop consumptive use data for an alfalfa crop assuming two center pivots would irrigate a total combined area of 326 acres. Consumptive water use for alfalfa was assumed to be 17.4 inches annually. This consumptive water use was distributed throughout the irrigation season as shown in Figure G.2-2. Assuming 20 percent evaporation losses from the center pivots, the annual flow through the center pivots for irrigation will be 21.7 inches per acre. Under normal operating conditions, the irrigation demand is assumed to have a seasonal distribution with irrigation beginning April 1 and continuing through October 31. Battle Mountain Resources, /nc. G-2 Telesto Solutions, /nc. PiProjectA2l2-Newmvnt(SaNUis)\SaN.vis\Fermit AmeMment - West Pil MmagemevtNelmiiAme~ddment_v3.dvc July 2006