Systems Analysis of Irrigation Water Management in Eastern Idaho

A water management study to include a complete water budget of the irrigated area of the Snake River fan in eastern Idaho was initiated in May 1970. The study was initiated to develop alternate management solutions to the increasing high water table problem causing inconvenience and financial hardships to local residents and to develop methods of solving regional groundwater problems. Water levels in wells raise as much as 40 feet during the irrigation season. A mathematical model of the gravel aquifer was developed utilizing alternating direction implicit procedures for finite difference solutions to the basic flow equations. Data on water table fluctuation, soils, crop distribution, irrigation diversions) distribution system losses and wastes evapotranspiration, and irrigation practices were obtained for input to the model. A dense network of canals with seepage rates averaging 3.5 cubic feet per square foot per day, irrigated soils with high infiltration rates, and in some cases inefficient irrigation practices contribute to diversions for irrigation significantly in excess of the state average. In 1970 the net diversion from the Snake River was 16.5 acre feet per irrigated acre and the net irrigation application was 9.6 acre feet per acre for the entire irrigation season. Continuing studies are underway to evaluate the response of the aquifer due to changes in inputs caused by canal lining or consolidation, drainage systems, and changes in water management procedure