Record snowpack melting could raise Lake Powell’s level by 71 feet
For the first time in five years, drought-depleted Lake Powell is spurting large amounts of water, repeating the spring floods that would naturally occur if the Colorado River were not dammed at Glen Canyon.
The US Bureau of Reclamation opened the gates at Glen Canyon Dam Monday, allowing up to 39,500 cubic feet per second, or cfs, to flow into the river channel at Lees Ferry, sending a tidal wave of water through the Grand Canyon. That’s like the contents of 27 Olympic-size swimming pools splashing through the bottom of the dam every minute.
“These experiments are really designed to recreate the habitat and physical features that would have existed downstream of the dam if the dam had not existed,” Amy Haas, executive director of the Colorado River Authority of Utah (CRAU), said to Last Weekly board meeting. “In this case, I’m talking about building up sandbars from accumulated sediments.”
The 72-hour experiment comes as Lake Powell begins to recover from a record low, while runoff from record-breaking snowpack begins to flow into the upper Colorado River.
Under a plan approved in 2012, the bureau conducted high-flow experiments almost annually through 2018. Since then, a series of dry years and excessive water consumption have depressed the level of Lake Powell, which is only 23% full today at 3,525 feet above sea level.
That will change drastically in the coming weeks as the upper Colorado Basin snowpack, which is 157% of normal, melts and flows into Powell and upstream reservoirs. According to Bart Leeflang, CRAU’s hydrologist, the lake level is expected to rise by more than 50 feet this year.
“If it’s time to be excited about hydrology, now is the time to be excited,” he said at last week’s board meeting. “It’s amazing what happened between March and April.”
What happened during those months was a large snowpack that grew in size and in some places contained twice the water that is usual for this time of year after years of little snow accumulation. According to Bureau forecasts, lake level is expected to peak at 3,591 feet in July, 71 feet above its historic low of April 13.
“A few years ago we were lamenting the fact that we lost 2 million acre feet from April to May [from Lake Powell]’ Leeflang said. “And now you see in March we collected 2 million acre-feet in two weeks.”
At 3,576 feet, Powell would still remain 124 feet under the full pool and only hold 39% of its capacity. This year’s bounty won’t end the crisis on the Colorado River, which feeds 40 million westerners and irrigates 5 million acres, but it will buy Utah and the six other basin states time to find a lasting solution to the river’s chronic deficits. It might even save boating this summer at Lake Powell, one of Utah’s top recreational attractions, where most ramps are high and dry and marinas unusable.
Average water flows on the river have declined in recent decades as global climate change makes the west warmer and drier while the region’s water needs continue to increase.
This year, the Bureau plans to increase Glen Canyon Dam releases to 9.5 acre-feet to raise the level of Powell’s big sister downstream, Lake Mead. That’s the maximum amount that will be released under the dam’s operational guidelines, and 2 million more than what is normally released in a year.
The large increase in projected “regulated” Lake Powell inflows, which are expected to total 13.2 million acre-feet, has allowed federal river managers to resume high-flow experiments.
“The 2023 water year was an exceptional hydrological period for the Colorado River basin. The high snowpack in the western United States was a welcome change after several years of severe drought conditions,” Wayne Pullan, the bureau’s regional director for the upper Colorado basin, wrote in an April 14 memo. “Last year’s low annual release rates have also resulted in large amounts of sand being retained in Marble Canyon, which is rapidly washed downstream in years of higher release rates.”
These sediments were intended to fill sandbars and beaches in the Grand Canyon, but the Glen Canyon Dam, completed in 1963, disrupted the natural processes driving them downstream, resulting in habitat loss for plants, animals, and fish.
Much of the water released during the experiments will bypass the dam’s eight hydroelectric turbines, but this will not result in an increase in the amount of water released from the dam.
With normal operations this April, dam clearances would fluctuate between 8,033 and 14,631 depending on the time of day, according to the bureau. This week’s high-flow experiment is the sixth since the agency began it in 2012.
In the five years since the last experimental publication, massive amounts of sediment have accumulated in Marble Canyon and where the Pariah and other tributaries meet the Colorado below the dam.
“Releases such as these are experimental in nature and are intended to provide a better understanding of how and when to integrate them into future dam operations to preserve or enhance beaches, sandbars and associated habitats,” the bureau said in a message release.
The Grand Canyon Monitoring and Research Center and the National Park Service will monitor the impact of high currents on the canyon’s beaches, fisheries, aquatic insects and archaeological sites.
In the meantime, the bureau is studying ways to adjust releases in Glen Canyon to prevent smallmouth bass, a non-native predatory fish, from escaping into the lower Colorado River and breeding in the Grand Canyon. Powell’s low water has allowed the species to pass the Glen Canyon Dam turbines and breed in the river below, where it has been able to prey on endangered native fish.