User:Greengreengreenred/AquiferDraft
The Spokane Valley-Rathdrum Prairie Aquifer is a mostly unconfined Sole Source aquifer located almost entirely within Spokane County, Washington and Kootenai and Bonner counties in Idaho.
Geology[edit]
The prehistoric Lake Missoula was a major Glacial lake formed during the most recent ice age and one of several glacial lakes formed by the Cordilleran Ice Sheet.[1] The Clark Fork ice dam allowed melted glacial water to pool to form the lake, which at greatest extent covered 3000 square miles and reached a depth of up to 2000 feet.[2] The lake went through a cycle whereby the Clark Fork dam would fail, causing either catastrophic flooding or noncatastrophic drainage into the Pacific Northwest; then ice would re-dam the lake, allowing it to refill; this cycle may have repeated itself up to 100 times.[3] It was the catastrophic floods, which deposited boulders, sand, and other generally porous sediment,[4] that formed the basis for the aquifer.[5] In large part, such deposits are present throughout the depth of the aquifer, allowing it to be classified as unconfined in those areas.[6]
However, in some places a layer of finer-grained, clayey deposits can be found. These deposits are of much lower porosity, and thus make the aquifer only partially unconfined in areas where they are found.[6] These sediments were deposited from drainage of two other glacial lakes in the area: Glacial Lake Columbia and Glacial Lake Spokane.[7] A USGS report suggests these sediments were deposited over a much wider area than that in which they are currently found, but that most of the deposits were eroded by subsequent floods from Lake Missoula.[8] Today, the largest and only significant portion of the aquifer known to be partially confined covers an area extending from a region known as the "Hillyard Trough" into the "Little Spokane Arm".[9]
Geography[edit]
The aquifer covers an area of about 370 square miles and provides water to over 500,000 people, including most residents of the cities of Spokane, Washington and Coeur d'Alene, Idaho.[10]
History[edit]
The aquifer was designated as a Sole Source aquifer by the Environmental Protection Agency on February 9, 1978.[11] Aquifers are declared "Sole Source" by the EPA if they meet two criteria: they must provide at least 50 percent of water consumed in the area they cover, and there must be no alternative source of water "which could physically, legally, and economically supply all those who depend upon" them.[11] Such designation was created under the Safe Drinking Water Act of 1974 to protect such aquifers from contamination; upon designation, federal funds can only be granted to future public works projects in the area so long as they do not pose a contamination risk that could "create a significant hazard to public health".[12]
Conservation[edit]
An average of 188 million gallons per day of water was estimated to be withdrawn from the aquifer in the year 2000, with totals in the summer reaching 450 million gallons per day.[13] The Clark Fork ice dam allowed melted glacial water to pool to form the lake, which at greatest extent covered 3000 square miles and reached a depth of up to 2000 feet.[14] This, along with the high rate of population growth in the region,[15], led to a joint effort by the United States Geological Survey, the Idaho Department of Water Resources, and the Washington Department of Ecology to improve scientific understanding of the aquifer.
References[edit]
- ^ Kahle, S.C., and Bartolino, J.R. 2007. "Hydrogeologic framework and ground-water budget of the Spokane Valley-Rathdrum Prairie aquifer, Spokane County, Washington, and Bonner and Kootenai Counties, Idaho". U.S. Geological Survey Scientific Investigations Report 2007-5041. p. 9-10.
- ^ Ibid., p. 10.
- ^ Ibid.
- ^ Ibid., p. 11.
- ^ Ibid., p. 12.
- ^ a b Ibid., p. 1.
- ^ Ibid., p. 11.
- ^ Ibid., p. 12.
- ^ Ibid., p. 1.
- ^ "Spokane Valley-Rathdrum Prairie Hydrologic Project". Idaho Department of Water Resources. Retrieved September 18, 2015.
{{cite web}}: External link in|publisher= - ^ a b "An Overview of the Sole Source Aquifer Protection Program in EPA Region 10". Environmental Protection Agency. Retrieved September 17, 2015.
- ^ Pub. L. 93–523; 88 Stat. 1679; 42 U.S.C. § 300h-3; § (e) et seq. 1974-12-16.
- ^ Kahle, S.C., and Bartolino, J.R. 2007. "Hydrogeologic framework and ground-water budget of the Spokane Valley-Rathdrum Prairie aquifer, Spokane County, Washington, and Bonner and Kootenai Counties, Idaho". U.S. Geological Survey Scientific Investigations Report 2007-5041. p. 1.
- ^ Ibid., p. 10.
- ^ Ibid.