A watershed is a geographic area that drains to a common point. Rain and melting snow drain from the ridges and hills down to the lowest point in the watershed, typically where stormwater empties into a river, lake or stream or sinks down (infiltrates) into the ground.
Watersheds may also be referred to as drainage basins and may vary in size. Watersheds or drainage basins may be defined by a small stream, covering only a few square miles, or they may be defined by a major river, such as the Columbia River, covering thousands of square miles.
Activities in a watershed can affect the quantity of stormwater emptying out of it. If natural land is covered by buildings and parking lots, more water will be channeled toward the outlet than if the land is left in a natural state. Undeveloped land accepts more stormwater into the ground and natural land features may retain stormwater until it can evaporate back into the atmosphere.
What happens to the land can also affect the quality of water emptying out of a watershed. Stormwater can carry pollutants into water used for bathing, drinking, cooking or swimming. If pollutants reach a high level, the water may no longer be safe for general use.
Greater Spokane County Watersheds
Although there are many defined watersheds in greater Spokane County, the watersheds noted in the left column are priority areas being focused on at this time.