Scientists have developed a three-dimensional depiction of the geology of the Columbia Plateau that will aid water resource managers coping with declining ground water levels, development and climate change in the region, according to a report published by the U.S. Geological Survey (USGS).

Ground water is a critical resource for the nearly 1.3 million people in the region, as well as providing irrigation water for the region’s estimated $6 billion-per-year agriculture. A recent USGS study showed that ground water levels of the Columbia Plateau have declined over the past 25 years in about 80 percent of the nearly 500 wells measured in the study.

To help resource managers in the region, in 2007, the USGS Groundwater Resources Program began a study of the Columbia Plateau Regional Aquifer System to answer key questions about widespread water-level declines, reductions in ground water flow into rivers, and the as-yet unknown effects of a changing climate on ground water resources.

As part of the study, USGS scientists built a three-dimensional geologic model – a computer model of geologic units – to define the overall aquifer system in the Columbia Plateau, to be used in a regional numerical model of ground water flow. The geologic model covers about 53,000 square miles of the Columbia Plateau in Washington, Oregon, and Idaho.

"The geologic model of the Columbia Plateau gives us a more complete picture of the shape and volume of the regional aquifer system," says Erick Burns, a USGS scientist working on the study. "This information will be used to build a ground water flow model to help water resource managers who are working on the issue of declining ground water levels in the region, and coping with changing development and climate conditions."

In addition to defining the geology of the aquifer system, USGS scientists also are documenting hydrologic changes and developing a water budget for the system. This information will help scientists build a ground water-flow simulation model that managers can use to test ways of managing the region’s ground water under different development and climate conditions.

This study and related ground water availability studies are being conducted nationally by the USGS through the Groundwater Resources Program. Information about the Groundwater Resources Program is available on-line at the USGS Web site.