Donna M. Cosgrove

Quantifying Ground-Water Pumping Impacts on Surface Water in Idaho

Idaho has embraced the concept of conjunctive management and the administration of surface and ground water rights in a common priority system. The means for quantifying impacts of ground water use on surface water resources is currently being developed. The process is complicated by the widespread effects of ground water use and the high degree of temporal attenuation of effects. One possible quantification method relies on the development and application of response functions. Response functions describing the temporal variation in river gains and losses resulting from ground water use have been developed from a numerical ground water flow model of the Snake River Plain aquifer. Response functions describing impact on each of several reaches of the Snake River are being aggregated to form zones throughout the aquifer. The response functions are proving to be useful educational tools for water users and managers and will be instrumental in the development of plans for mitigating ground-water pumping impacts on senior surface water users.