Spokane Valley - Rathdrum Prairie

Science Center Objects

The Spokane Valley/Rathdrum Prairie aquifer, which extends across Idaho and Washington, is the sole source of drinking water for more than 450,000 people. Recently submitted water-rights requests would substantially increase withdrawals from the aquifer. The public and state resource management agencies need an improved understanding of the SVRP hydrologic system in order to ensure appropriate management and protection of this valuable resource. In close cooperation with water-resource agencies and stakeholders from Idaho and Washington, the USGS is conducting a major study of the aquifer to provide current, complete scientific information for making good decisions about managing this important aquifer.

9722-B2V - Spokane Valley - Rathdrum Prairie Hydrologic Study - Completed FY2007

Problem - The Spokane Valley - Rathdrum Prairie (SVRP) aquifer represents the sole source of drinking water for over 400,000 residents in Spokane County, Washington, and Kootenai County, Idaho. The area includes the rapidly growing cities of Spokane, Spokane Valley, and Liberty Lake, Washington, and Coeur d'Alene and Post Falls, Idaho. Recent and projected urban, suburban, and industrial/commercial growth has raised concerns about potential future impacts on water availability and water quality in the SVRP aquifer and Spokane and Little Spokane Rivers. Water resource concerns include growing demands on ground water and declining ground-water levels, low streamflow in reaches of the Spokane and Little Spokane Rivers, and water-quality problems associated with changing land use activities. Management of the SVRP aquifer system is complicated by the interstate, multi-jurisdictional nature of the system.

Objectives - The purpose of this study is to gain a better understanding of ground-water and surface-water resources in the SVRP area. This study will provide an improved scientific basis for evaluating water management alternatives for the SVRP aquifer and Spokane and Little Spokane Rivers. This study will provide the means for estimating the effects of additional ground water and surface water withdrawals on the SVRP aquifer and Spokane and Little Spokane Rivers, as well as simulating potential effects of climate change on water resources in the area. This study also will establish a network of dedicated monitoring wells for long-term collection of ground-water level and water-quality measurements, and will develop a common regional database for analyzing current and future ground-water and surface-water questions.

Relevance and Benefits - The project addresses many issues identified in the USGS Water Resources Program’s Strategic Plan (http://pubs.usgs.gov/of/1999/ofr99-249/html/exec.html#H001) for meeting the nation’s water-resources needs. These issues include availability and sustainability assessments of America’s water resources, estimating effects of land use and management alternatives on water quantity, and determining effects of ground-water withdrawals on surface water. Water availability and ground-water/surface-water interactions are critical to the SVRP study and are also major water-resource issues identified in the Washington District’s Science Plan. Study of the SVRP aquifer is complicated by the interstate nature of the aquifer; thus, the USGS serves a critical role in supporting the impartial collection and analysis of water-resource data by working with the States of Washington and Idaho to develop resource-management tools that are mutually acceptable to both States and a diverse stakeholder community. There is high transfer value to the partnering process used to achieve the study objectives, and the tools developed in this study can be used in similar hydrogeologic settings.

Approach - Tasks that will be conducted to achieve the project objectives include:

  1. Compile, review, and evaluate published reports, numerical models, and database records describing the geology, hydrogeology, aquifer characteristics, and water-budget components of the SVRP aquifer and adjacent geologic units, and streamflow records for the Spokane and Little Spokane Rivers.
  2. Collect additional data necessary for the construction of a ground-water/surface-water flow model.
  3. Construct and calibrate a regional ground-water/surface-water flow model of the SVRP aquifer area.
  4. Demonstrate model capabilities using several hypothetical water-management scenarios on the SVRP aquifer system.

Several other studies of the SVRP aquifer and Spokane River system are currently underway. These studies are supported by a variety of federal, state, local, and private funds. Data collection for the SVRP aquifer study will be coordinated with the principal investigators of these studies to ensure that all available aquifer-related data are collected and synthesized into the SVRP aquifer study database and to eliminate the duplication of efforts.