This dataset contains the boundary of the Wood River Valley aquifer system as modified and expanded from that defined by Skinner and others (2007): It has been extended farther up several tributary canyons, extended up the Big Wood River to include a number of wells near the mouth of Baker Creek, expanded to include the western side of the Poverty Flat area, and extended slightly downstream of Stanton Crossing and Picabo. Although most of the boundary delineated by Skinner and others (2007) has been retained here, modifications were made in places to include information from additional wells that penetrated bedrock below alluvium.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. References cited:Bartolino, J.R., 2009, Ground-water budgets for the Wood River Valley aquifer system, south-central Idaho: U.S. Geological Survey Scientific Investigations Report 2009-5016, 36 p.Skinner, K.D., Bartolino, J.R., and Tranmer, A.W., 2007, Water-resource trends and comparisons between partial development and October 2006 hydrologic conditions, Wood River Valley, south-central Idaho: U.S. Geological Survey Scientific Investigations Report 2007-5258, 31 p., 4 plates, 1 appendix.