How Colorado River Affects Farming
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River Overview
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It's a long way between the Colorado River's birthplace in the high Never Summer Mountains (in Colorado's Rocky Mountain National Park)--which may see 20 feet of snow a year--to its arid mouth in the Gulf of California. The river is 1,450 miles, to be exact. The upper Colorado is burgeoned by big mountain tributaries like the Gunnison, the Green and the San Juan; lower desert streams like the Gila and the Virgin add comparatively little water but much sediment.
Climate and Agriculture
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The Colorado's 246,000-square-mile basin covers much grand scenery, from glacially carved peaks to dizzying canyon labyrinths. On the whole, it's also fairly strapped for water. Most of Colorado, for example, receives but 12 to 16 inches of annual precipitation. Much of the upper basin is high, cold and dry; much of the lower is true desert. The highest precipitation falls in the mountains, mostly as snow, and the majority of the water in regional rivers derives from that source.
Without irrigation, large-scale agriculture in the Rockies, Colorado Plateau, Great Basin and Mojave and Sonoran deserts would be severely restricted at the very least. Flow alteration and diversion of Colorado River water, therefore, vastly changes the agricultural dynamic of the region.
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Irrigation
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Over two-thirds of the Colorado River system's water goes to irrigation. Tens of millions of people in seven states and Mexico depend on the river. Beginning in the early 1900s, the federal government initiated an ambitious alteration to the Colorado River flow, building dams and diversions to generate hydropower, disperse water for agriculture and municipalities and to attempt to standardize hydrological resources. In addition to the construction of one of the world's first major impoundments, the Hoover Dam, this included aqueducts and canals that transport some of the Colorado's water well beyond its basin. Today, the river supports the existence of cities like Las Vegas, Los Angeles and Phoenix. Agricultural operations east of the Continental Divide in Colorado are supplied by some of the river's water via the Colorado-Big Thompson Diversion Project. The Imperial Valley (formerly called the Valley of the Dead) of southern California produces crops because of the All-American Canal.
Concerns
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The extensive manipulation and utilization of the Colorado River has long been a subject of concern for conservationists. A major issue is salinization, which has been increasing in the Colorado for decades. The river becomes saltier because of evaporation in its reservoirs. Irrigated water also concentrates salt through evaporation and due to leaching through naturally alkaline soils of the arid basin, which are then returned to the river. This trend threatens some of the country's most important agricultural areas, like California's San Joaquin and Imperial valleys, in addition to those in Mexico along the far lower Colorado. Global warming--which may impact precipitation and snowpack--is also a threat, potentially diminishing the Colorado's volume on which so much agricultural (not to mention ecological) productivity relies. Between 2000 and 2005, the water level in Lake Powell, an artificial reservoir of the Colorado in Arizona, decreased by two-thirds.
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