Rathdrum-Spokane Aquifer

The sole source of water for 500,000 people, the aquifer is a high quality underground water body.  Discovered in 1895, this aquifer has become one of the most important resources in the region.

The aquifer has one of the fastest flow rates in the United States, flowing as much as 50 feet per day in some areas.  In comparison, a typical aquifer has a flow rate between 1/4 inch and five feet per day.  The aquifer begins in Idaho between Spirit Lake and the south end of Lake Pend Oreille.  It flows south until it reaches the middle of the Rathdrum Prairie, where it turns west and flows into Washington under the Spokane Valley.  When the aquifer water reaches downtown Spokane, most of it turns north, flows under the city and discharges into the Little Spokane River through springs.  A strong relationship exists between the aquifer and the Spokane River throughout the river's length from Lake Coeur d'Alene in Idaho to the confluence with the Little Spokane River in Washington state.

The aquifer has long been considered an inexhaustible supply of pure water.  However, with the rapid growth occurring in the region, water is no longer unlimited in supply.  Current water policies and management practices will need to be reconsidered to meet the complex and challenging task of shifting away from the perception of an inexhaustible source to one with limits.

The Rathdrum-Spokane Aquifer is highly vulnerable to contamination.  Unlike many other aquifers, the Rathdrum-Spokane Aquifer does not have protective layers of clay or rock to deter infiltration of surface contaminants.  The soil layers above the aquifer are relatively thin in most of the 322 square miles it covers. Fluids readily infiltrate into the porous sands and gravel that comprise the aquifer materials.  Potential contamination is the most important aquifer issue that must be addressed to preserve and maintain the aquifer as a regional drinking water resource.  Sources of contamination over the aquifer are varied and abundant.  Examples are: septic systems, wastewater, stormwater, landfills, and industrial spills.