FEATURE
Groundwater in the Intermountain West: An Essential Resource
Delmas W. Johnson
THE INTERMOUNTAIN WEST has principally an arid climate due to its geography away from the coasts and internal to the North American continent. The prolific mountainous areas including those in the Great Basin, provide for orographic precipitation and a precious annual snowpack that promotes watershed infiltration and storage. History of Water in the West. Historically, the West was populated by nomadic Native Americans who lived where adequate water and food was present. As the western United States was settled by emigrating Europeans and eastern-originating Americans during the 19th and early 20th centuries, the communities developed where a sufficient water supply was found. Most of the communities throughout this area have their beginnings near a surface water source that could be developed and diverted for domestic and irrigation uses. Canals and ditches were constructed to provide water to these newly established communities and settlements. The more obvious and simpler surface water sources
conditions existed, wells were constructed to access that flowing groundwater. However, immediately after the war, there occurred a marked shift to groundwater development
to provide further access to needed water supply. Aquifers . The Intermountain West has extensive alluvial aquifers created by millennia of erosion and degradation of its mountain ranges. The impacts of the most recent Pleistocene ice age also contributed to sediment deposition and historic lake formation. Therefore, the hydrology of these forming watersheds created an opportunity for the Groundwater is an essential source of water supply in the Intermountain West, and a strong complement to available surface water sources.
development of groundwater within the fractured bedrock and volcanic rocks which in turn provide substantial recharge to expansive alluvial deposits. Precipitation and seasonal snowpack also recharge these alluvial aquifers. These aquifers are valuable to water users in the west in that groundwater is generally more prevalent than surface water bodies. Deeper aquifers are not impacted by evapotranspiration caused by deep-rooted vegetation. One can construct a well and pump groundwater
to a desired location rather than be limited by the location of the surface water source. With regard to providing safe drinking water, it has been much less costly to develop a groundwater source that typically does not require any water treatment to meet safe drinking water standards. Most directly withdrawn groundwater has been safe for the public to consume and only requires proper disinfection and good system management. Impacts from Drought. Groundwater accounts for 40% of U.S. freshwater consumption. In Utah, 25% of the total water supply comes from groundwater sources, but 54%
Figure 1. Diverted surface water flowing through a canal (Photo credit: Courtesy of U.S. Bureau of Reclamation)
were identified, developed and put to beneficial use prior to World War II. There were some efforts to develop groundwater sources prior to the war, but they were limited due to lack of electrical power distribution and limitations on pump and motor technology at the time. Where artesian
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Water Resources IMPACT
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