Grand Canyon advocates are celebrating a decision by federal water managers to unleash a three-day pulse of high water from Glen Canyon Dam to rebuild beaches and improve environmental conditions on the Colorado River. The high-flow experience is scheduled to start Monday.
Environmentalists, river runners and others had sought such a flood release, outlined under the dam’s adaptive management program, for years. Healthy monsoon rains had pushed tons of sand into the river, but had also gouged the beaches and sandbars that create natural backwaters and campsites for river trips. Opening the dam’s floodgates before the fresh sediment gradually washed downstream could push the sand up to form new beaches.
Their efforts previously ran into the reality of declining water behind the dam in Lake Powell, where the U.S. Bureau of Reclamation was trying to hold back enough water to keep generating hydropower. In response under the Grand Canyon Protection Act of 1992, the agency can release floodwaters when the Paria River dumps sufficient sand below the dam, but had not done so since 2018. This winter, the Rocky Mountains piled up more snow than at any time since 2011, with enough water content to raise the reservoir by dozens of feet.
Reclamation's Upper Colorado Region confirmed the plan on Tuesday. On Friday, the agency sent interested parties a memo explaining its decision to go ahead with a 72-hour release of extra water beginning Monday. Dam operators will open bypass tubes to roughly quadruple the river’s flow to 39,500 cubic feet per second.
Wayne Pullan, the agency’s Upper Colorado regional director, wrote in a memo announcing the decision on Friday that the big snows will enable larger total flows from Lake Powell to Lake Mead, on the other end of the Grand Canyon, and are “a welcomed change following multiple years of severe drought conditions.”
“It’s a happy day,” said Lynn Hamilton, executive director of Grand Canyon River Guides, a river recreation advocacy group. “I’m sure the river-running community will be happy to have beaches to camp on this season.”
Springtime flows mimic the river's natural cycle
Watching the last few years pass without a big dam release to rebuild beaches has been frustrating, she said, because there was plenty of sand accumulated to make one worthwhile. But she acknowledged the difficult spot that Reclamation has been in, trying to balance competing interests such as hydropower, rafting and endangered species. There was fear that conducting a flood last fall, when water temperatures were warm, could help push non-native smallmouth bass downstream and into position to munch on protected humpback chubs. Young bass were found downstream of the dam last year, triggering an emergency response to remove as many as possible.
With colder water that shouldn’t favor the warm-water invaders, a pulse is not expected to harm native fish. Still, for longer-term native fish conservation, Reclamation is considering altering future flows and using barriers such as nets to keep more bass from slipping through Glen Canyon Dam’s turbines.
The government has conducted several such high-flow experiments in the past, but this will be the first to occur in spring, the natural time for flooding before Glen Canyon Dam’s completion in 1963.
“A springtime (flood) is an opportunity to see all the natural processes that are kicked in by a high flow and see how they respond,” said Kelly Burke, who directs Wild Arizona’s Grand Canyon Wildlands Council.
Burke had originally hoped for a series of cold blasts later in spring or summer, specifically to push young bass away from the protection of their parents. Since then, the forecasts for higher runoff into Lake Powell have suggested that colder water could flow through the dam for months to come, likely harming bass reproduction. That’s because a fuller reservoir raises the warm surface layer, allowing colder water from the depths to spill through.
Reclamation officials told advisory committee members last week that the agency will back away from the anti-bass flows for this year after receiving thousands of public comments, including from small utilities that use Glen Canyon’s power around the West. Instead, it will conduct a fuller environmental study of the idea for next year. Meantime, pulse planned for Monday is expected to help control bass.
Concerns about power, fish
One group worried about changing flows for fish was the Colorado River Energy Distributors Association. Because flows targeted at bass would draw colder water through the dam's bypass tubes, which lack hydropower-producing turbines, they would reduce the dam's potential to make power that benefits millions throughout the West. It would also raise environmental justice questions, the association's executive director, Leslie James, wrote in a comment submitted to Reclamation, because 53 tribal energy providers are among those affected.
“I understand the (environmental) concerns,” James told The Arizona Republic, acknowledging that 25,000 raft trip campers a year are affected when they lack adequate camping beaches. But more power consumers are affected when the water is released without generating electricity, which raises the cost of power secured from more expensive sources. “The water and hydropower resources have also been significantly impacted for more than five years. Any bypass is a direct impact to the hydropower resource.”
The planned blast could help reduce another worrisome invader — brown trout — around Lees Ferry, said Jim Strogen, president of Trout Unlimited’s Gila Trout Chapter. Brown trout spawn in fall and winter, and forcing the resulting eggs or young from the nest’s protection should help limit their numbers, he said.
“They’re fun to catch, but they’re problematic in terms of their potential hazard to native fish downstream,” Strogen said.
Brown trout also feed on young rainbow trout, which might be one reason that recent surveys have turned up relatively few young rainbows, he said. Rainbows are also non-native to Grand Canyon and Lees Ferry, but are a long-established and popular sportfish that is considered less likely to eat native fish. It’s possible that a spring flood could help rainbows, in part by harming browns.
“This is a short-term win for us,” Strogen said of the impending flood. If the drought resumes and reservoir levels decline again in future years, a long-term fix is needed to protect the Grand Canyon.
Environmental coverage on azcentral.com and in The Arizona Republic is supported by a grant from the Nina Mason Pulliam Charitable Trust. Follow The Republic environmental reporting team at environment.azcentral.com and @azcenvironment on Facebook, Twitter and Instagram.
You can support environmental journalism in Arizona by subscribing to azcentral today.
This article originally appeared on Arizona Republic: Federal dam managers to unleash Grand Canyon flood