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September 15th, 2010

New Tool Guides Skagit Groundwater Plans

TACOMA, Wash. — Skagit River Basin water managers now have a computer model to run “what-if” simulations to evaluate the potential effects of groundwater withdrawals on streamflows in the basin, particularly in summer months when water in tributaries is from groundwater, according to a report released today by the U. S. Geological Survey.

The report was produced in cooperation with Skagit County Public Works Department, Washington State Department of Ecology, and Skagit County Public Utility District No. 1.

“This model provides a much-needed tool that forms a solid, scientifically-based foundation on which informed decisions can be made regarding the use of water resources in these basins,” said Gary Stoyka, Skagit County Senior Hydrogeologist.

“The model provides a useful tool to determine how water consumed from wells affects stream flows,” said Jacque Klug, Ecology’s regional supervisor for water resources. “We will use the model to determine if we should change how we calculate reservation water use.”

Today's new report is the fourth and final report on the exchange of water between streams and the groundwater-flow system in the lower Skagit River Basin. USGS scientists found that most of the late summer streamflow in the tributary subbasins comes from the local aquifers.

The USGS study area covers about 247 square miles along the lower Skagit River and its tributary subbasins (East Fork Nookachamps Creek, Nookachamps Creek, Carpenter Creek, and Fisher Creek) in southwestern Skagit County and northwestern Snohomish County. Water level measurements and geologic information from 296 water wells helped scientists defined the basin's groundwater-flow system. Streamflow measurements from 27 locations were used to analyze the exchange of water between streams and the groundwater-flow system.

The report, "Numerical Simulation of the Groundwater-Flow System in Tributary Subbasins and Vicinity, Lower Skagit River Basin, Skagit and Snohomish Counties, Washington," by Kenneth H. Johnson and Mark E. Savoca, is published as U.S. Geological Survey Scientific Investigations Report 2010-5184 and is available on the Web at http://pubs.usgs.gov/sir/2010/5184/ .