Geography of the Colorado River Basin
The Colorado River flows nearly 1,450 miles through seven US states and Mexico. With a drainage basin of approximately 246,000 square miles, the river irrigates 5.5 million acres of agricultural land and provides water for nearly 40 million people.
Stereograph of the Colorado River, below the Paria River in Arizona. 1872.
The Colorado River originates in the high Rockies and flows down the West side of the Continental Divide, southwest across the Colorado Plateau and through seven US states in the arid American West until it ultimately reaches the river’s final output, or mouth, at the Colorado River Delta in the Mexican state of Baja California- this is the region where the Colorado River flows into the Gulf of California. The primary source of Colorado River water is precipitation, from storms that “build snowpacks that melt in late spring, providing runoff to the Colorado River” [1]
The management of Colorado River water involves a number of diversions that route the course of the water, as well as dams and reservoirs which restrict the movement of said water. The Glen Canyon Dam impounds Lake Powell, which provides the Upper Basin with water storage, while downriver, the Hoover Dam impounds Lake Mead, providing the Lower basin with water storage.
A number of historical compacts, treaties, legislative actions, and policy recommendations attempt to meet the needs of all stakeholders along the Colorado River. The cornerstone document of this body is the 1922 Colorado River Compact, which set out to allocate water resources to Colorado River users. The Colorado River Basin was split into two divisions- the upper division, or Upper Basin, includes Colorado, New Mexico, Utah and Wyoming, and the lower division, or Lower Basin, includes Nevada, Arizona, and California. The dividing line between the Upper and Lower Basins is downstream from Lake Powell at Lees Ferry- it is at this point where a stream gauge determines allocations for the Upper and Lower Basins.
The Colorado River is under existential threat, as record drought persists in the American West. Even if the total input to the Colorado river were to increase, snowfall alone “isn’t likely to alleviate the drought” [2]. The threat of drought is compounded by inter-basin water supply issues and the tug-and-pull between municipal and agricultural users for water access.
References
Image 1: Library of Congress, LC-DIG-stereo-1s00261
[1] https://pubs.usgs.gov/fs/2004/3062/
[2] https://thehill.com/changing-america/sustainability/climate-change/3830354-why-the-snowfall-in-colorado-rockies-isnt-likely-to-alleviate-the-drought/
