U.S. Cities: Las Vegas and Tucson [North America]
The Ogallala Aquifer is the largest known aquifer in the world. It lies underground beneath eight states, extending from South Dakota and Wyoming in the north to Texas in the south. Before depletion became a problem, it held more water than all of the freshwater lakes, streams, and rivers on Earth.
The Ogallala Aquifer. (Click to enlarge)
The main cause for depletion is irrigation for farming. This area of the United States produces 20% of the U.S.’s agricultural output. The government has encouraged this level of production with subsidies. For example, it has supported growing cotton, a plant that requires large amounts of water, along with providing crop-disaster payments and tax breaks that allow heavy groundwater use. In addition, while the Ogallala Aquifer contains a large volume of water, it is replenished slowly- so much so that it is considered a nonrenewable resource. Most of the present water is the same water that was stored at the end of the last ice age. In some areas, the water is withdrawn at eight to ten times the recharge rate, leading some experts to predict that the 25% of the aquifer will be depleted 2020.
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Some solutions have been suggested in order to slow the rate of depletion. Farmers have had success using more efficient irrigation systems, raising crops that require less water, and irrigating less land. In Texas, employing better irrigation technology led to a 2-25% decrease in water use. Furthermore, as resources have decreased, the cost of drilling and pumping costs have increased, causing an overall decline in total irrigated area. Finally, better technology for all uses of water in the states on the Ogallala Aquifer will help preserve this resource for years to come.
