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Know the West

The incredible shrinking Colorado River

Climate change and rising demand are sucking the life out of the Southwest’s water supply.

One of the most visible signs of the state of the West’s water supply is the big bathtub ring around the sandstone rim of Lake Powell, the nation’s second-largest reservoir. Whenever the massive hydrological system that delivers water to the lake dwindles, the whitewash halo grows, shrinking only when — or rather, if — that system is replenished by rain and winter snows.

 

By July 23, the halo occupied some 150 vertical feet of shoreline, showing that the lake’s surface had fallen to its lowest level since 1969, before it was completely filled for the first time. Boat-launch ramps, which had already been extended repeatedly, were finally unusable. The hydropower-generating capacity of Glen Canyon Dam was in danger of disappearing altogether. Even more worrisome, though, is what the diminishing reservoir tells us: The Colorado River watershed is terminally ill.

Two decades of climate change-induced drought and rising temperatures, combined with ever-growing demand, have put the entire water system — and the flora and fauna and more than 40 million people that rely on it — into serious trouble. Now local, state and federal water managers are being forced to reckon with a frightening reality: the incredible shrinking Colorado River system.

 

1922
The year the Colorado River Compact was signed, divvying up the river’s water between the Upper Basin states — Wyoming, Colorado, Utah and New Mexico — and the Lower Basin — Arizona, Nevada and California.

90%
Proportion of the system’s water that originates in Upper Basin states.

16.52 million acre-feet
The quantity of surface and groundwater withdrawn from the basin in 2010.

13.6 million acre-feet
Amount of that year’s total used for irrigation.

8.62 million acre-feet
The average annual “unregulated inflow” into Lake Powell from 2000-2021. (Unregulated inflow means the approximate natural flow, i.e., the Bureau of Reclamation’s estimate of how much water would run into the lake without upstream diversions or withdrawals.)

3 million acre-feet
Projected unregulated inflow to Lake Powell during the 2021 water year (Oct. 1, 2020, to Sept. 30, 2021).

5.2 million acre-feet
Quantity of water diverted out of the basin and into other watersheds — largely to provide water to urban areas such as Denver, Albuquerque and Los Angeles — in 2010.

$803 million
Value of hay grown in Colorado River Basin states and exported in 2020, mostly to China and Saudi Arabia.

328,000 acre-feet
Consumptive use of Colorado River water for thermo-electric power production (coal and natural gas) in 2010. (Consumptive = water that isn’t returned to the stream after use.)

372,000 acre-feet
Approximate amount of water that evaporated from Lake Powell in 2020.

35,000 acre-feet
The amount of water that will be delivered to the Colorado River Delta this year for environmental restoration.

25.8 million acre-feet
Amount of water in Lake Powell as of July 14, 1983.

7.9 million acre-feet
Amount of water in Lake Powell as of July 25, 2021.

Visitors walk at Lone Rock Beach in Big Water, Utah, by Lake Powell, in an area that used to be underwater. Two decades of climate change-induced drought and rising temperatures, combined with ever-growing demand, have put the entire water system in serious trouble.
Justin Sullivan/Getty Images

Map by Alison DeGraff Ollivierre, Tombolo Maps & Design/High Country News

Infographic design: Cindy Wehling. Sources: U.S. Bureau of Reclamation, U.S. Geological Survey, Pacific Institute, U.S. Drought Mitigation Center, Utah Board of Water Resources, Central Arizona Project, Colorado Parks and Wildlife, Colorado Department of Natural Resources, Dolores Water Conservation District.

Jonathan Thompson is a contributing editor at High Country News. He is the author of River of Lost Souls: The Science, Politics and Greed Behind the Gold King Mine Disaster. Email him at [email protected] or submit a letter to the editor.