Water Management and Groundwater in the Henry's Fork--Upper Snake River Basin of Idaho

A water resource study of the Lower Henry's Fork area and the Upper Snake River Basin in Idaho was undertaken to evaluate the hydrological relationships between the perched and regional groundwater tables, river reach-gain and irrigation water management. Data on irrigation system diversions and return flow, cropping patterns and water use, and river flows were used to evaluate a basin water budget for the area. For the 1975 water year the net recharge from the study area to the Snake Plain regional aquifer is estimated to be 509,000 acre feet or approximately 8 percent of the tota 1 input to the aquifer. Manipulation of the perched water table to effect sub-irrigation in sandy soils on some areas of the basin requires canal diversions in excess of 11 acre feet per acre and causes rises in the water table of 2-40 feet over the season. A groundwater model of the perched system is being developed and will be integrated with the current model of the Snake River Fan aquifer to the south of the Henry's Fork