Wet year promises to boost Colorado River reservoirs, ecosystems

The network of pipes and massive bathtubs that is the Colorado River Basin's reservoir storage system is going to see some recovery this year thanks to higher-than-average snowpack. That's a promising sign for aquatic habitats in need of a health boost.

Overuse and a 23-year drought have drawn down the water stored in reservoirs across the basin, which spans seven states, 30 Native American tribes and part of Mexico. Recently, one of the basin's largest reservoirs, Lake Powell, even needed emergency releases from upstream reservoirs, including Blue Mesa Reservoir in western Colorado, to safeguard against a looming crisis.

As most water officials and experts will emphasize, one good year of snow won't solve the crisis. But this year, the system's largest reservoirs will end the year with more water than they had at the start, and water managers don't foresee any need for drought-related releases from Blue Mesa.

Which means, as upstream reservoirs benefit from the wet year, there might be more opportunities for releases that help manage river sedimentation and bolster downstream ecosystems, said Bart Miller, healthy rivers director at Western Resource Advocates.

"Having years that do have really high flow helps counterbalance the years with low flows," Miller said. "It helps scour out the channels; it helps get rid of some of the riparian vegetation that might otherwise encroach; it helps with spawning cues for all sorts of native species."

The Colorado River Basin is in the midst of its worst drought in about 12 centuries, according to recent research, and years of drought-response planning haven't been enough to avoid a water security crisis. In total, the reservoir system can store about 58 million acre-feet of water, according to the Bureau of Reclamation. In March, that system held about 19 million acre-feet, or about 32% of its capacity. An acre-foot is enough water to supply two to three U.S. households for a year.

In 2021 and 2022, water managers sent drought-response releases totaling 624,267 acre-feet downstream to shore up Lake Powell after its water supply fell to critical levels, along with the supply at Lake Mead. If the reservoirs drop below certain water levels, Hoover Dam and Glen Canyon Dam can't generate hydroelectric power. If levels fall too low, the dams can't send water downstream at all.

This year has offered temporary relief. Much of the Upper Colorado River Basin, which includes Colorado, New Mexico, Utah and Wyoming, saw above-average snowpack, and in some places, it even neared record levels. That's a boon for farmers, residents of cities, recreators and other water users across the whole basin, which provides water to about 40 million people.

The wet year will help slightly replenish the system's reservoirs. Lake Powell is estimated to receive about 12.9 million acre-feet of water from spring runoff to add to its current storage, according to the 24-month study released this month by the U.S. Bureau of Reclamation, which manages operations of the federal reservoir. By the end of December, the water level of Lake Powell is projected to be at around 3,573 feet — still a long way from its full capacity of 3,700 feet, or about 26 million acre-feet of water but better than the near-crisis level in 2022. At that time, the lake's elevation was 3,536 feet and it stored about 6.64 million acre-feet of water.

The federal government and basin states have myriad plans in place to try to avoid letting Lake Powell fall below 3,525 feet in an effort to maintain a buffer. Below 3,490 feet in elevation, Glen Canyon Dam near the Utah-Arizona border can't produce hydroelectric power, and below 3,370 feet, it can't send water downstream to Lake Mead, a state known as dead pool.

"Things are looking good right now. We’re not at imminent risk of hitting dead pool, and that's great," said Amy Ostdiek, interstate, federal and water information chief for the state's top water agency, the Colorado Water Conservation Board. She warned that the situation could go downhill quickly in just a few dry years. "We need to not lose sight of the need to have plans in place for if that happens."

The bureau plans to send about 9.2 million acre-feet down to Lake Mead, just east of Las Vegas, which hit 1,046 feet in March, its lowest point this year. The lake's highest elevation is about 1,219 feet, and it can't generate hydroelectric power below about 950 feet in elevation.

Mead is projected to end the year at about 1,066 feet in elevation and to release about 8.1 million acre-feet down to the millions of water users in the Lower Basin states of Arizona, Nevada and California. Some of the water released from the two reservoirs is allocated for Mexico.

"I think having a wet year provides more flexibility for the Lower Basin to prop up Mead, and we’re hoping that they take full advantage of that opportunity," Ostdiek said.

With more-than-normal amounts of water coming down from the mountains, water officials are focused on refilling reservoirs.

Of the emergency releases sent to Lake Powell, about 36,000 acre-feet came from Blue Mesa, Colorado's largest reservoir, and 588,267 acre-feet came from Flaming Gorge Reservoir at the Utah-Wyoming border. By April 2024, both reservoirs are projected to recover the full amount of water released, according to the Bureau of Reclamation's 2023 drought response plan which went into effect Friday.

The plan emphasizes that the focus is on recovery — and that there are no planned drought-related releases for the reservoirs this year. If adjustments need to be made, they will take place first at Glen Canyon Dam, then at Flaming Gorge, Blue Mesa — which is part of the three-reservoir Aspinall Unit — and Navajo Reservoir, which is at the Colorado-New Mexico border, according to the plan.

The emergency releases in 2021 set back some local businesses around Blue Mesa, particularly during the dry 2022 season, said Celeste Helminski, executive director of the Gunnison County Chamber of Commerce.

"It was a hard summer out there for those people who rely on the lake," she said. "This year is definitely looking better. The whole morale of people who are lake users and rely on the lake for their economy — everyone is definitely happier."

In 2022, a local marina couldn't open because of the low water levels. Boaters couldn't launch, and the campgrounds weren't as full. Retail shops also took a hit, said Andy Cochran, who manages a local sporting goods store. His dive and outfitting business, GSO Fishing, didn't take as much of a hit, he said.

"Our guide service is already super booked up for the whole summer and the sporting goods store, Gene Taylor's, has already seen an uptick in sales around the lake," he said.

None of the three reservoirs are projected to reach their full capacity this year, but some will get close, according to the bureau's 24-month study.

"I think we’re at the point now where we’re starting to see the 24-month study really tell us how the rest of the year is going to play out," Ostdiek said, adding that the study is most helpful for near-term decision making. It also sheds light on factors that influence some Bureau of Reclamation decisions, and the August report is used to set reservoir operations for the next year.

According to the May study, Blue Mesa is projected to peak in July at about 7,514 feet, just below its capacity of 7,519 feet. Navajo Reservoir will peak in May at 6,060 feet, about 25 feet below its full capacity of 6,085 feet. Flaming Gorge will rise to its highest elevation in July at about 6,028 feet. Its capacity is 6,040 feet.

"We’re fortunate that this year's good snowpack has given us the ability to not call on these reservoirs for additional releases but instead focus on storing water as it comes in to recover the amounts that were previously released," Ostdiek said.

The spring runoff has damaged roads, caused flooding and sent hundreds of rafters to southwestern Colorado for the rare opportunity to raft the Dolores River. But water officials and environmental organizations are also plotting how they can use water releases to benefit the environment.

"In most cases those decisions haven't been made yet," Ostdiek said. "I think we’re kind of at the wait-and-see phase where we are looking at runoff and watching flooding risk."

Some releases have already started. In April, water managers began releasing a surge of water from Glen Canyon Dam for environmental purposes. The release is part of an experiment to restore sandbars, beaches and campsites — and potentially rehabilitate river wildlife — along the Grand Canyon.

In Colorado, the Dolores Water Conservancy District is timing its recreation-focused releases from McPhee Reservoir to help the downstream ecology.

Different flows have different benefits, like clearing out sediment, helping with cottonwood seeding, potentially removing overgrowth and flushing out smallmouth bass, said Ken Curtis, the district's general manager.

"There are decades of study behind this. We do different levels of flows depending on how much water we have," he said.

Similar projects are taking place along rivers around Colorado and beyond, like the Lower Gunnison below Blue Mesa and the Aspinall Unit, which made its own releases this month. On the Green River below Flaming Gorge Reservoir, water managers are sending down surges of water to either flush out nonnative fish while they’re still small enough to be swept downstream or to help push native fish larvae into backwater habitats where they can grow into adults, said Miller of Western Resource Advocates.

In the mainstem of the Colorado River inside Colorado, there's a 15-mile segment near Grand Junction, above the confluence with the Gunnison River, where flows during the summer can get really low.

Some years the stretch of river doesn't see very high peak flows in the spring, but in a year like this, upstream reservoirs have enough water coming in that they have to spill some, he said.

"They can time those releases or spills to be together so the river has a real surge, more of a natural peak flow that's almost mimicking what the river might’ve looked like 150 years ago before there was any large-scale diversions," Miller said.

The coordinated operations lead to a higher peak flow than otherwise possible. Those higher peak flows help give spawning cues to endangered fish and generally renew the habitat for fish in the 15-mile reach.

Later in the season, there will be opportunities to use stored water to help increase base flows. At times, the river's flows can be so shallow that the water increases in temperature or there's a loss of connectivity between pools where the fish are living, he said. "Those stored volumes are available some years, but not others. It depends on the year, but a wetter year will probably mean that there will be more opportunities to send water down from places like Ruedi Reservoir," Miller said, a reservoir east of Basalt.

Shannon Mullane writes about Western water issues for The Colorado Sun and her work is funded by a grant from the Catena Foundation. She focuses on the Colorado River Basin, tribal affairs related to water, and West Slope water issues.Born in East Tennessee, Shannon has been in... More by Shannon Mullane