The Rathdrum-Spokane Aquifer begins at Spirit Lake and the south end of Lake Pend Orielle in Idaho. From there the aquifer travels south until it reaches the Rathdrum Prairie. From the prairie it turns west and crosses into the state of Washington underneath the Spokane Valley. The Rathdrum-Spokane Aquifer is considered an inexhaustible supply of water.
The Rathdrum-Spokane Aquifer has one of the highest flow rates in the country, with the water sometimes flowing up to 50 feet a day. By comparison, most aquifers flow between a quarter-inch and five feet a day. The aquifer travels directly underneath the city of Spokane and, via springs, discharges water into the Little Spokane River.
Most aquifers have protective layers of clay or rock that prevent contamination from the surface. The Rathdrum-Spokane Aquifer does not, making it highly vulnerable to contamination. The sands and gravel that make up the aquifer are frequently infiltrated by fluids such as wastewater, storm water, industrial spills and septic system drainage.
The water in the Rathdrum-Spokane Aquifer is supplied or, more accurately, recharged, through precipitation, runoff and leakage from surrounding lakes. The water elevation is over 2,000 feet near Lake Pend Oreille, and lowers to just under 2,000 feet at the Idaho-Washington state line. The water depth ranges from 150 to 600 feet.
