New Tools and Knowledge to Aid in Columbia Plateau Groundwater Management

TACOMA, Wash. — A comprehensive report published today by the U.S. Geological Survey provides new knowledge and tools to aid in the management of critical Columbia Plateau resources while coping with declines in groundwater levels and the uncertainties of climate change. 

Groundwater from the 44,000 square mile Columbia Plateau Regional Aquifer System has declined since the 1970s, but is a vital resource for nearly 1.3 million people in Idaho, Oregon and Washington, as well as supplementing irrigation water for the region’s estimated $6 billion annual agricultural industry.

“The Columbia Plateau Regional Aquifer System is large, complex and relied upon heavily by residents, farmers, cities and industry,” said Sue Kahle, USGS hydrologist and co-author of the report. “The information gained during this study and the new flow model provide a better understanding of the system, as well as a tool to assist agencies manage this essential resource.” 

Scientists used the information gathered in the study to build a groundwater flow simulation model that water officials can use to test ways of managing the region’s groundwater under different pumping and climate conditions. 

Among the important findings of this new model are:

• Groundwater pumping has increased substantially since the 1970s and 1980s, resulting in declining water levels and decreasing groundwater flows to rivers over much of the study area.
• During dry to average precipitation years, groundwater pumping causes a net loss of groundwater in storage. Groundwater pumping presently exceeds recharge during all but the wettest of years.

To document changes in the aquifer system USGS scientists compiled water levels measured in approximately 60,000 wells over the last 100 years. The collected data shows that from 1968 to 2009, 72 percent of all wells declined, with an average rate of 1.9 feet of decline per year.

Water-resource issues, with implications for future groundwater availability, found during the study include:

• Widespread water-level declines associated with the development of groundwater resources for irrigation and other uses.
• Reduction in groundwater base flow to rivers and the associated effects on water temperature and quality.
• Limited availability of non-appropriated surface water.
• Potential capture of surface water appropriated through senior water rights by pumping of groundwater appropriated through junior water rights.
• Effects of climate change and variability on pumping demands, groundwater recharge, base flow in rivers, and ultimately, sustainable groundwater yields. 

Agencies cooperating in the collection of groundwater data used in the report include the Columbia Basin Ground Water Management Area, Confederated Tribes of the Umatilla Indian Reservation, Oregon Water Resources Department, U.S. Department of Energy, Walla Walla Basin Watershed Council and Washington State Department of Ecology. More information about the study is available at the USGS Columbia Plateau Groundwater Availability Study website.

The report, “Groundwater availability of the Columbia Plateau Regional Aquifer System, Washington, Oregon, and Idaho” and a companion fact sheet that summarizes the report, U.S. Geological Survey Fact Sheet FS-2015-3063, are available online.