THE HEADWATERS OF the Colorado River are located in Rocky Mountain National Park in north central Colorado. Its drainage area extends into seven western states: Wyoming, Utah, Colorado, Nevada, Arizona, New Mexico, and California. The river’s 1,450-mile course through the arid southwest to its delta on the Gulf of California has it descending from 9,000 feet to approximately 100 feet. The river runs southwest across Colorado from its origin, continues through southwest Utah, crosses into northern Arizona through the majestic Grand Canyon, and then heads south along the border with both Nevada and California before entering Mexico between Baja California and Sonora. Seven states and part of Mexico all share in the water delivered by the Colorado River. In some years, there is barely a trickle of water as the river enters the Mexican area. In drought years, the riverbed is literally dry miles short of the delta.
In Utah the river becomes the natural sculptor of the uplifted Colorado Plateau. The unique landforms found in Arches National Park, Dead Horse Point State Park, and the Canyonlands National Park is attributed to the work of the Colorado River and its tributaries. In Colorado, the Glen Canyon Dam was constructed to provide hydroelectric power to the local area. Page, Arizona, a new town adjacent to the dam site, came into being as a result. Lake Powell, the reservoir behind the dam, began filling in 1966 and reached its maximum capacity in the mid-1980s. Since that time, due to long-term drought conditions in the Southwest, Lake Powell has receded more than 20 feet from its high point.
Just below its confluence with Nevada’s Virgin River, the Hoover Dam was constructed. Behind this giant structure is Lake Mead, which supplies water to thriving metropolitan Las Vegas. Two additional dams are located along the Arizona–California border: the Palo Verde Diversion Dam and the Imperial Dam. They were built to provide irrigation water for agricultural activities in the remote stretches of desert. The Imperial Valley in southern Arizona receives its water from the All-American Canal, a channel constructed to divert Colorado River water to this exceptionally fertile but excessively dry agricultural area.
A potentially serious environmental situation involving the accumulation of radioactive mining tailings near Moab, Utah, was resolved in 2005. Uranium has been mined in the region for 40 years, and the pilings were stored a mere 800 feet from the Colorado River. Although no river pollution has been reported, there was concern over the years that the river could be degraded if seepage occurred from the accumulated pilings. In July 2005, the Department of Energy formalized a plan to transfer the uranium pilings to Crescent Junction, 20 miles northwest of its present site and safely away from any potential contamination of the Colorado River.
Allocation of Colorado River water was an early concern shared by the seven states in the region. On November 24, 1922, representatives signed the Colorado River Compact, an agreement which apportioned water between upper and lower river basin states. The upper basin included Wyoming, Colorado, Utah, and New Mexico. The lower basin states are California, Nevada, and Arizona. According to the plan, each basin was scheduled to receive 7.5 million acre-feet of water per year. The amounts of water specified implied availability during years of normal precipitation. There have been a significant number of years since inception that lower amounts of precipitation were received. In years of deficit, legal entanglements and disputes have emerged, especially among the states in the lower basin.
To simplify the allocation situation, each basin was authorized to determine the amount of water for each of its states. In the upper basin, a contract signed in 1948 assigned each state with the following percentage allocation: Colorado: 52, Utah: 23, Wyoming: 14, and New Mexico: 11. Development in the upper basin has proceeded at a much slower rate than in the three states to the south. Consequently, none of the upper basin states have used their full allocation of Colorado River water. At the end of the allocation chain is California, the state using the greatest amount of water from the Colorado River. California’s population is expected to increase significantly over the next two to three decades virtually assuring greater draw on the limited water delivered by the Colorado River.
Grand Canyon; Hoover Dam; Lakes; United States, California; Water Demand.
Relief: ~4100 m Basin area: 642,000 km 2 Mean discharge: 550 m 3 /s (virgin) ~40 m 3 /s (present) Mean annual precipitation: 22...
Relief: 1195 m Basin area: 103,341 km 2 Mean discharge: 75 m 3 /s Mean annu. precipitation: 82 cm Mean air temp.: 20°C Mean...
The Colorado River is small compared to many rivers in the United States, but as the largest river in the arid Southwest, it is a source of vital wa