What Are the Costs and Benefits of Damming a River?
ESU401  Irrigation

Water from the Colorado River is used to irrigate cropland in seven western states, but not directly around Lake Powell. This image illustrates that the bare sandstone plateaus and canyons around the lake are not well suited for agriculture. Distributing water for irrigation of crops is not part of Glen Canyon Dam's operations.

NASA
Lake Powell is in a region of sandstone plateaus and canyons that is not well suited for agriculture.

Farther downstream, below the Grand Canyon, Colorado River water is diverted into canals to water huge agricultural areas in Nevada, California, and Arizona. Only a fraction of the water that flows through the Grand Canyon ever makes it to the Gulf of California. Glen Canyon Dam's function for irrigation is to store a supply of water for lands downstream of the dam that might otherwise suffer during droughts.

Consider the overall impact of Glen Canyon Dam on providing irrigation for crops. In the chart on your student answer sheet, use a scale from -2 to +2 to indicate your evaluation of the dam for providing irrigation.


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