{"id":2301,"date":"2016-06-07T20:26:02","date_gmt":"2016-06-07T20:26:02","guid":{"rendered":"https:\/\/courses.lumenlearning.com\/geologyxwaymakerxmaster\/?post_type=chapter&p=2301"},"modified":"2025-10-13T17:13:58","modified_gmt":"2025-10-13T17:13:58","slug":"reading-groundwater-withdrawal","status":"publish","type":"chapter","link":"https:\/\/courses.lumenlearning.com\/geo\/chapter\/reading-groundwater-withdrawal\/","title":{"raw":"Reading: Groundwater Withdrawal","rendered":"Reading: Groundwater Withdrawal"},"content":{"raw":"
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Is it good to make the desert bloom?<\/strong><\/p>\r\n

Many sunny, arid regions are good for growing crops as long as water can be added. Some of the increase in productivity is due to farming in regions that are technically too dry. Groundwater can be used to make the desert bloom, but at what cost? And for how long? Eventually the wells will run dry.<\/p>\r\n\r\n<\/div>\r\n

Groundwater Overuse<\/h2>\r\nSome aquifers are overused; people pump out more water than is replaced. As the water is pumped out, the water table slowly falls, requiring wells to be dug deeper, which takes more money and energy. Wells may go completely dry if they are not deep enough to reach into the lowered water table.\r\n\r\n[caption id=\"attachment_2364\" align=\"aligncenter\" width=\"720\"]\"Map Figure 1. Intense drought has reduced groundwater levels in the southern U.S., particularly in Texas and New Mexico.[\/caption]\r\n\r\nOther problems may stem from groundwater overuse. Subsidence and saltwater intrusion are two of them.\r\n

Ogallala Aquifer<\/h2>\r\nThe Ogallala Aquifer supplies about one-third of the irrigation water in the United States. The Ogallala Aquifer is widely used by people for municipal and agricultural needs. (Figure 2). The aquifer is found from 30 to 100 meters deep over an area of about 440,000 square kilometers!\r\n\r\n[caption id=\"attachment_2365\" align=\"aligncenter\" width=\"363\"]\"Map Figure 2. The Ogallala Aquifer is found beneath eight states and is heavily used.[\/caption]\r\n\r\n[caption id=\"attachment_2366\" align=\"alignright\" width=\"192\"]\"Satellite Figure 3. Farms in Kansas[\/caption]\r\n\r\nThe water in the aquifer is mostly from the last ice age. About eight times more water is taken from the Ogallala Aquifer each year than is replenished. Much of the water is used for irrigation .Farms in Kansas use central pivot irrigation (Figure 3), which is more efficient since water falls directly on the crops instead of being shot in the air. These fields are between 800 and 1600 meters (0.5 and 1 mile) in diameter.\r\n

Subsidence<\/h2>\r\nLowering the water table may cause the ground surface to sink. Subsidence may occur beneath houses and other structures.\u00a0The San Joaquin Valley of California is one of the world\u2019s major agricultural areas. So much groundwater has been pumped that the land has subsided many tens of feet.\r\n

Salt Water Intrusion<\/h2>\r\n

When coastal aquifers are overused, salt water from the ocean may enter the aquifer, contaminating the aquifer and making it less useful for drinking and irrigation. Salt water incursion is a problem in developed coastal regions, such as on Hawaii.<\/p>\r\n\r\n

Summary<\/h2>\r\n
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  • When water is pumped from an aquifer, the water table declines and wells must be drilled deeper.<\/li>\r\n \t
  • The Ogallala Aquifer was filled in the ice age but is being used to irrigate the farms of the Midwestern U.S. at a rate far greater than it is being replenished.<\/li>\r\n \t
  • Ground subsidence and saltwater intrusion are two possible consequences of groundwater overuse.<\/li>\r\n<\/ul>\r\n
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    Practice<\/h3>\r\nUse this resource to answer the questions that follow.\r\n\r\n