The concrete wall of Glen Canyon Dam is 710 feet tall, poured from nearly 5 million cubic yards of concrete and locked into solid sandstone. It could stand for a thousand years. The lake behind it may not last that long.

Since the diversion tunnels closed in 1963, the Colorado River has been carrying tens of millions of tons of sand, silt and mud into Lake Powell every year. For decades it stayed hidden under hundreds of feet of water. In 2026, as the lake fell to its lowest level since it first filled, the mud came into view: walls of sediment up to 150 feet tall, stranded marinas, and deltas creeping steadily toward the dam.

In this video, we go inside one of America's biggest engineering projects. We follow the blast triggered from Washington, the tunnels that turned the Colorado River, the canyon walls bolted together from the inside, and the concrete poured around the clock for more than three years. Then we look at the slow, unstoppable process that is filling the reservoir in, and what happens if the lake drops below the level where the dam can no longer make power.

Note: sediment timelines are estimates and vary widely between researchers and agencies. Lake levels change daily; figures reflect conditions as of September 2026.

📚 SOURCES & FURTHER READING

Glen Canyon Dam history and construction (U.S. Bureau of Reclamation)
https://www.usbr.gov/uc/rm/crsp/gc/

Lake Powell (construction timeline, cost, workforce)
https://en.wikipedia.org/wiki/Lake_Po...

Glen Canyon Dam construction details (Lake Powell Country)
https://www.lake-powell-country.com/G...

The 1983 spillway crisis (ASDSO Dam Failures and Lessons Learned)
https://damfailures.org/case-study/gl...

Sedimentation in Lake Powell (National Park Service)
https://www.nps.gov/glca/learn/nature...

Sediment pushing into Lake Powell, USGS findings (Salt Lake Tribune)
https://www.sltrib.com/news/2022/04/2...

Will Lake Powell become Lake Mud? (Salt Lake Tribune)
https://www.sltrib.com/news/environme...

Lake Powell's growing sediment crisis (Deseret News via Great Salt Lake Collaborative)
https://greatsaltlakenews.org/latest-...

"Mud glaciers," sand waves and the Dominy Formation (St. George News via Great Salt Lake Collaborative)
https://greatsaltlakenews.org/latest-...

Cataract Canyon rapids returning (Rolling Stone)
https://www.rollingstone.com/culture/...

Cataract Canyon river conditions, Hite and North Wash (National Park Service)
https://home.nps.gov/cany/planyourvis...

Colorado River system during historic drought (U.S. Bureau of Reclamation)
https://www.usbr.gov/newsroom/news-re...

Lake Powell drops to record-low levels, 2026 (NASA Earth Observatory)
https://science.nasa.gov/earth/earth-...

Flaming Gorge releases to stabilize Lake Powell (Newsweek)
https://www.newsweek.com/lake-powell-...

America's reservoirs are filling up with mud (Bloomberg)
https://www.bloomberg.com/graphics/20...

The world's dams are filling up, UN-backed study (The Revelator)
https://therevelator.org/dams-sedimen...

All Dams Are Temporary (Practical Engineering)
https://practical.engineering/blog/20...

💬 Do you think Lake Powell will still be working in 100 years, or has the river already won?

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