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(1)http://pubs.usgs.gov/ha/ha730/ch_c/C-text3.html (2)http://nevada.usgs.gov/barcass/index.htm (3)http://pubs.usgs.gov/circ/1323/pdf/Circular1323_book_508.pdf

Introduction
The Basin and Range aquifers are a group of aquifers covering about 200,000 square miles and lying under seven states including: Nevada, California, Oregon, Utah, Idaho, New Mexico, and Arizona. Some of the basins are closed, not allowing water that flows in to leave, while others are open permitting water to flow between basins. The Basin and Range serve as the main source of ground water in both western Utah and southern Arizona, and it is the 4th most used aquifer for ground water use. The depth of the individual basins vary widely, with most being between 1,000 to 5,000 feet deep, while a few in Arizona and Utah may be as much as 10,000 feet deep.

Groundwater Recharge
The basins are largely filled by precipitation falling in the mountains surrounding the aquifers, although due to the arid climate throughout the region where the basins are located, it is estimated that only 5% of precipitation may actually recharge the aquifer. Much of the rest of the precipitation is lost due to evapotranspiration. In Utah, recharge to one basin can often come from another basin in the system that may be at a higher elevation, although little information on the amount of interbasin flow exists. Other sources of basin recharge may be irrigation applied to golf courses and agricultural land. In Arizona about half of irrigation water was estimated to return to the aquifers.

Groundwater Discharge
Discharge comes from both natural and unnatural sources. Evapotranspiration is one of the larger causes of discharge due to the prevailing climate in the region. Especially in Utah where the water table is shallow, plants which draw water from the basins can transpire much of this water. Other sources of discharge include outflow to streams or rivers, flow into other basins, and removal by wells. Withdrawl of water can change the dynamics in the system of aquifers, causing flows to change, or outflow to streams to stop as the water table drops below the level of a stream bed. In some areas, ground water withdrawl has caused large drops in the water level, particularly in agricultural regions. In some parts of Arizona the water level dropped more than 450 feet by 1980, while in some parts of Utah it dropped by 70 feet. Average rates of decline in less developed regions of Arizona and Utah were about 5 feet per year, while in more developed areas of souther Arizona they reached 20 feet per year. The rate of water decline has generally been lower since 1970 as more efficient irrigation systems have been adopted and crops that need less water have been cultivated. However, growing populations in areas such as Phoenix and Tucson in Arizona, and Provo in Utah put pressure on the system and exhibit the largest ground water withdrawl. As water is withdrawn and water levels drop, soil previously saturated can compact causing subsidence, and in some cases fissures in the earth can develp ranging from a fraction of an inch wide to 10 feet wide in some cases.