Direct-current resistivity soundings and exploratory drilling suggest that the basalt of the Snake River Group is relatively thin in the area along the Snake River that is topographically suitable for pumping large quantities of ground water in exchange for surface water. The formations underlying the Snake River Group appear to have low permeability and probably would not yield large amounts of water. Previous studies have indicated that the southern edge of the Snake Plain aquifer extended to the Snake River. Data presented in this report implies that, in general, the southern boundary should, in fact, be several miles north of the river.