We are Unbelievably Screwed

The second largest reservoir in the United States, Lake Powell is in danger of having its level fall so low that the flow of the Colorado river will simply stop.

There would still be a lake over 100 miles long behind the dam, but the level of the water would be below the lowest outlet from the dam, so even that meager supply would simply sit and evaporate.

The consequences would be catastrophic, leading to immediate mass water shortages for 10s of millions of people:

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Back then, the idea of draining Lake Powell was fringe, attractive to anti-government extremists and radical environmentalists. Those who advocated a legal decommissioning of the Glen Canyon Dam, including supporters of the Glen Canyon Institute in Salt Lake City, were often laughed out of the room.

In those years, the dam was working as intended. Lake Powell was nearly full in the late ‘90s. Hydropower production was going full tilt, and millions of people were visiting the reservoir annually to fish, houseboat, and water ski.

But since the year 2000, Lake Powell has been in decline. Climate change has reduced runoff throughout the Colorado River Basin by around 20% compared to the previous century. In 2022, the reservoir — the second-largest in the country after Lake Mead — was less than a quarter full.

Nearly every boat ramp on Lake Powell was unusable last spring, and there was barely enough water to sustain hydroelectric generation. One more bad snow year would have pushed the Colorado River system to the brink of collapse, dropping the reservoir’s surface toward the lowest outlets on the Glen Canyon Dam–a point known as “dead pool.”

That’s because there is a significant design flaw in the dam: There is no drain at the bottom. Billions of gallons of water would be trapped in the dead-pool reservoir with no easy way to release them into the Grand Canyon.

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At dead pool, the 27 million people who rely on Colorado River water downstream from the dam would likely be forced to reduce water use quickly and involuntarily.

But Lake Powell would still stretch 100 miles into Glen Canyon at dead pool.

At some point in the not too distant future, we will discover that large swaths of the United States, and the rest of the world, will no longer be able to accommodate their current population densities. 

There may be some technical fixes out there, but I do not see them as being sufficient support the viability Lake Powell, or for that matter, the entire Colorado river basin.

BTW, you can find an academic article discussing this here.