About the Aquifer
The sole source of water for most people in Spokane County in Washington and Kootenai County in Idaho, the EPA designated the aquifer as a "sole source aquifer" in 1978. It was the 2nd Aquifer in the nation to receive this special designation and it increased public awareness for aquifer protection and supported the development of special management practices by local agencies. Practices such as eliminating septic tanks and pre-treating stormwater over the Aquifer have greatly improved water quality over what it was 40 years ago.
The Aquifer underlies about 370 square miles in 2 states. It has one of the fastest flow rates in the United States, flowing as much as 60 feet per day in some areas. The volume of the entire Aquifer is about 10 trillion gallons, making it one of the most productive aquifers in the country. Note, however, that the Aquifer is not simply an "underground river", a common misconception. It is a combination of gravels, cobbles and boulders - the result of the rapid draining of Glacial Lake Missoula when ice dams broke. Water from adjacent lakes, mountain streams, the Spokane River and precipitation flow through these flood deposits supplying the Aquifer.
The surface outlet for Lake Coeur d'Alene is the Spokane River, which is the only watercourse over the Aquifer that remains on the surface for an extended distance. Only Hangman (Latah) Creek and the Little Spokane River flowing out of the surrounding highlands actually reach the Spokane River. Other streams contact the course, gravelly soils overlying the Aquifer and disappear, percolating downward.
Aquifer Atlas Library
For comprehensive information about the aquifer, its geologic formation, its relationship to the Spokane River and much more, check out the SVRP Aquifer Atlas Library
You can also visit the County's Groundwater Monitoring Program web page
for current water quality and quantity information.