Ground-water reconnaissance in Round Valley, Custer County, Idaho

Round Valley in central Idaho contains alluvial deposits of Pleistocene and Recent age which yield adequate supplies of ground water for stock and domestic wells. The alluvial deposits are underlain by Challis Volcanics of Oligocene or Early Miocene age and a few wells obtain domestic and stock water from the basalt, iatite, andesite, and rhyolite which are the principal rocks in the Challis. Very crude estimates indicate that the average annual recharge to the alluvium and Challis Volcanics from precipitation and irrigation is 50,000 acre-feet.

Geologic and well data suggest that sufficient ground water might be obtained for irrigation supplies at some places.