Estimated Altitude of the Consolidated Rock Surface Underlying Quaternary Sediments of the Wood River Valley aquifer system, South-Central Idaho

This dataset is the estimated altitude of the consolidated rock surface underlying Quaternary sediment of the Wood River Valley aquifer system. This surface is composed of the top of pre-Quaternary bedrock and Quaternary basalt, Wood River Valley, south-central Idaho. This surface was constructed using the depth of bedrock from about 1,000 well-driller reports for boreholes and about 70 Horizontal-to-Vertical Spectral Ratio (HVSR) ambient-noise measurements of the Wood River Valley aquifer system, south-central Idaho. Bedrock depths were subtracted from the altitude of land surface obtained from the 2009 1-Arc Second National Elevation Dataset and the resulting points were used to construct an estimated bedrock surface altitude with hand-drawn 100-ft contour interval. These contours were then used to create a raster surface of the estimate altitude of the bedrock surface as described in the procstep section below. This dataset was created in support of the third phase of a continuing U.S. Geological Survey (USGS) study to assess the groundwater resources of the Wood River Valley, south-central Idaho. The first phase was documented in "Water-resource trends and comparisons between partial development and October 2006 hydrologic conditions, Wood River Valley, south-central Idaho" (Skinner and others, 2007), and the second phase was documented in "Ground-water budgets for the Wood River Valley aquifer system, south-central Idaho"(Bartolino, 2009). The third phase is a description of the hydrogeologic framework of the Wood River Valley aquifer system. The Wood River Valley contains most of the population of Blaine County and the cities of Sun Valley, Ketchum, Hailey, and Bellevue. This mountain valley is underlain by the alluvial Wood River Valley aquifer system. The entire population of the area depends on groundwater for domestic supply and rapid population growth since the 1970s has caused concern about the long-term sustainability of the groundwater resource.