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Water Resources at Hoover Dam
One glance at Hoover Dam will reveal a most obvious fact - there's a lot of water behind the dam. You might think that there is enough water for thousands of years. Actually, there is enough to supply 29 million households (about equal to the population of California) for one year. In the regions of the Southwest where people are water wise, Lake Mead could supply twice this many families with water for one year.
The Colorado River is more than 1400 miles in length, making it the third longest river in the United States. The watershed covers more than 244,000 square miles, 1/12 of the area of the lower 48 states. Although the river begins in the Rocky Mountains, most of its length drains the arid Southwest region.
This river is an important source of water to seven western states - Colorado, Wyoming, New Mexico, Utah, Arizona, Nevada, and California, as well as a portion of Mexico. Along the way it is used for irrigation, domestic water, recreation, and hydroelectric power production. These uses would not be possible if not for the series of dams along the Colorado river and its tributaries.
Just after the turn of the century a succession of floods broke through levees just above the border with Mexico. The resulting flood waters created the Salton Sea in southern California and inundated much of the Imperial Valley. On the other hand, drought years reduced the river to a trickle. In order to supply water to the arid Southwest, a series of dams along the Colorado River was devised. These dams would act as flood control, silt control, and water storage units.
Hoover Dam was the first of the large reclamation projects along the Colorado River. The dam backs up the waters of the river to form Lake Mead. Lake Mead is the largest man-made lake (reservoir) in the United States, holding almost 29 million acre feet of water. An acre-foot of water is the amount of water that will cover an acre, one foot in depth. This water is stored behind Hoover Dam and is used throughout the Southwest. The dam also helps to settle out silt and reduce the amount of sediment sent down the river.
At Lake Mead, the sediment will usually drop out where the lake starts to form at the west end of the Grand Canyon. If the water coming through the canyon is moving fast enough, like after a heavy rain, then the sediment will be carried farther into the lake before it settles to the bottom. It is estimated that 60 to 90 feet of sediment (or silt) now lies behind Hoover Dam. Eventually, enough of this sediment may come down the river to fill up the whole lake, but we don't expect that to happen for hundreds of years.
For now, the dam does it's job of slowing down the river so water can be stored in Lake Mead. As we've seen, this also "cleans" the water by allowing the dirt to settle to the bottom of the lake.
Water is a top priority at Hoover Dam. Without water, life in the desert would be impossible. Hoover Dam, as well as other dams along the Colorado River, make the storage of this precious water possible.
50 Simple Things Kids Can Do To Save The Earth; The EarthWorks Group; Andrews and McMeel, Kansas City; 1990.
HydroExplorer, The Colorado River Run; IBM and Mac versions; Water Education, Sacramento, CA.
Life Science Library, Luna B. Leopold, Kenneth S. Davis; Time, Inc, NY; 1969
The Magic School Bus at the Water Works; Joanna Cole; Scholastic, Inc, NY, NY; 1986.
Water: the Power, Promise, and Turmoil of North America's Fresh Water; National Geographic Society, Washington D.C., Nov. 1993.
What Makes It Rain? The Story Of A Raindrop; Keith Brandt; Troll Associates, Mahwah, NJ; 1982.
Where Does Water Come From?; C. Vance Cast; Barrons Educational Series, Inc., Hauppauge, NY; 1992.
Source - U.S. Department of the Interior - Bureau of Reclamation