Department of
Environmental Quality

The Rathdrum Prairie Aquifer (RPA) is a deposit largely made up of sand, gravel, cobbles, and boulders. The RPA extends south from the Bonner-Kootenai County boundary toward the cities of Coeur d'Alene and Post Falls and west to the Idaho-Washington state line. The aquifer extends into Washington and becomes part of the larger Rathdrum-Spokane Aquifer.

Water recharges the RPA through precipitation, runoff from the surrounding upland areas, and leakage from surrounding lakes. The water table is at an elevation of about 2,060 feet near Lake Pend Oreille and about 1,980 feet at the Idaho-Washington state line. The larger Rathdrum-Spokane Aquifer supplies drinking water to approximately 100,000 people in Kootenai County, Idaho and another 400,000 people in Spokane County, Washington.

Evolving Use of the Aquifer

From its first use as a source of irrigation water for agricultural development to the area's primary source of drinking water, the Rathdrum Prairie Aquifer has played a key role in sustaining the Coeur d'Alene Region. Learn more.

Aquifer Boundary

The boundary of the Rathdrum Prairie Aquifer is defined differently among various government agencies. DEQ has classified the RPA as a sensitive resource aquifer, following the boundary defined by EPA. Because of this classification, all activities that could impact the water quality of the RPA must be carried out so they maintain or improve existing quality of the ground wate. Learn more.

Geologic History

When was the Rathdrum Prairie Aquifer formed? Only about 70 or 80 million years ago! Learn more.

Hydrogeology

Hydrogeology is the study of water under the earth’s surface. The Rathdrum Prairie Auifer is mainly made up of coarse sand, gravel, cobbles, and boulders, although areas of fine-grained silt and clay sediments can also be found. Learn more.

Water Quality

To evaluate general trends in aquifer ground water quality, the Panhandle Health District collects water quality samples from 33 wells three times a year. Access well data here.

Weather

Weather conditions — temperature, rain, humidity, and wind speed — can have a big influence on how much precipitation is available to recharge the water in the aquifer. The Bureau of Reclamation's AgriMet network collects weather data and reports on crop water use. Learn more.

Educational Tools

Lesson plans and animations about the Rathdrum Prairie Aquifer are availqable to teach elementary school children about this important natural resource. Link to curriculum.

Reports and Publications

A multitude of scientific reports and publications on the hydrogeology and geology of the Rathdrum Prairie Aquifer is available here.

Links

Want to learn more? Visit the websites listed here.