Ground-Water Resources of the Wood River Valley, South-Central Idaho

Big Wood River above Sun Valley, Idaho
—November 18, 2004

Introduction

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 which consists of a single unconfined aquifer that underlies the entire valley, an underlying confined aquifer that is present only in the southernmost valley, and the confining unit that separates them. The entire population of the area depends on ground water for domestic supply, either from domestic or municipal-supply wells, and rapid population growth since the 1970s has caused concern about the long-term sustainability of the ground-water resource.

Purpose and Scope

The objectives of this USGS study are to:

• Provide data and interpretations about the water resources of the Wood River Valley to enable county and local governments to make informed decisions about those resources.
• Identify any additional water-resources data collection or studies needed to support decision makers.

The first phase of the 2005 work plan, compilation of ground-water level maps for partial-development and 2006 conditions, the change between them, and an analysis of hydrologic trends in the ground- and surface-water systems, was completed in 2007 (Skinner and others, 2007). The second phase of the work plan, development of a ground-water budget for the aquifer system, was completed in 2009 (Bartolino, 2009).