As Powell Shrinks, Glen Canyon's Power Output Falters; 2014 Bill For Spot Power Buys $62 Million [View all]

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It took 17 years for the reservoir to fill; 19 years later, a steady decline began. Thanks to the steady overuse of the Colorado River system — which provides water to one in eight Americans and supports one-seventh of the nation’s crops — Lake Powell has been drained to less than half of its capacity as less water flows into it than is taken out.

That relative puddle is no longer capable of generating the amount of power the dam’s builders originally planned, and so the power has become more expensive for the government to deliver, with the burden increasingly falling on the nation’s taxpayers. In 2014 the agency managing power at the dam spent $62 million buying extra power on the open market to make up for shortfalls. The dam’s power sales are relied on to pay for the operations of other, smaller, dams and reservoirs used for irrigation in the West, and as Glen Canyon crumbles financially, so might the system that depends on it.

But it is not just the reservoir’s overuse that is causing it to shrink. More than 160 billion gallons of water evaporate off Lake Powell’s surface every year, enough to lower the reservoir by four inches each month. Another 120 billion gallons are believed to leak out of the bottom of the canyon each year into fissures in the earth — a loss that if tallied up over the life of the dam amounts to more than a year’s flow of the entire Colorado River.

In all, these debits amount to “the largest loss of water on the Colorado River,” Mr. Beard said, enough to supply some nine million people each year. Glen Canyon is not the only dam to fall out of favor. Other major projects are also being decommissioned or re-evaluated. The Hoover Dam’s Lake Mead, which on Wednesday fell to its lowest level ever, some 145 feet below capacity, also loses hundreds of billions of gallons to evaporation and is now 37 percent full. The lake behind Arizona’s Coolidge Dam, one of the state’s largest reservoirs, is virtually empty.

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http://www.nytimes.com/2016/05/22/opinion/unplugging-the-colorado-river.html?_r=0