USGS Washington Water Science Center
|U.S. Department of the Interior
U.S. Geological Survey
Release: December 7, 2005
[Note: The report can be viewed on the Web at http://pubs.water.usgs.gov/sir20055227/ .]
Information needed by scientists to build an accurate, representative flow model of the Spokane Valley- Rathdrum Prairie aquifer is collected into a new report published by the U.S. Geological Survey (USGS).
Prepared in cooperation with the Idaho Department of Water Resources and the Washington Department of Ecology, the report summarizes past and present scientific knowledge about the aquifer as a first step in building a flow model of the aquifer.
Water managers need the flow model to help make decisions affecting the Spokane Valley-Rathdrum Prairie aquifer, which underlies nearly 370 square miles in Idaho and Washington and is the primary source of drinking water for the nearly 400,000 residents in the two-state area.
The report describes previous investigations of the aquifer, including studies of the area’s hydrogeology and geologic history, physical characteristics of the aquifer, and interactions between ground water and surface water.
"Compiling the current knowledge of the aquifer is important for two main reasons," said Sue Kahle, USGS hydrologist and lead author of the report. "It gathers all the existing information that we need to put together a flow model of the aquifer. It also identifies knowledge gaps that we need to address."
Some of the gaps include how deep the aquifer is at key locations, and how ground water might be flowing out of the aquifer at its downstream end near the Little Spokane River and Long Lake.
From the 1930's through the 2000's, there have been several studies of water resources in the Spokane Valley and Rathdrum Prairie. Some are regional, and some others are site-specific, but each has added to the understanding of the aquifer.
"Each of these studies has helped build a considerable body of knowledge about the aquifer, which is summarized in the report," Kahle said.
USGS water science in Washington and Idaho began over a century ago. In 1890, the USGS started measuring the streamflow at its gage on the Spokane River at Spokane, the oldest continuously operating gage in the state. Streamflow measurements by the USGS in Idaho began in 1889 on the Big Wood River. The USGS well in Spokane County has been used to monitor ground water since 1921. In Idaho, the USGS now has a real-time monitored well in Kootenai County. Ground water level information is available for Idaho as far back as 1928.
The report, "Compilation of Geologic, Hydrologic, and Ground-Water Flow Modeling Information for the Spokane Valley-Rathdrum Prairie Aquifer, Spokane County, Washington, and Bonner and Kootenai Counties, Idaho," by Sue C. Kahle, Rodney R. Caldwell, and James R. Bartolino, is published as U.S. Geological Survey Scientific Investigations Report 2005-5227. The report can be viewed on the Web at http://pubs.water.usgs.gov/sir20055227/. Copies can be purchased from the U.S. Geological Survey, Information Services, Box 25286, Federal Center, Denver, CO 80225-0286, telephone 303-202-4200.
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