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Glen Canyon Dam High Flow Experiment

Water rushes out of bypass tubes in Glen Canyon Dam during the Bureau of Reclamation's 2013 high flow experiment. A new 20-year plan for management of dam operations calls for high flow releases to be performed on an annual basis if the right conditions exist. 

Environmental groups are criticizing the final draft of a plan released by the Bureau of Reclamation Friday to manage the operations of Glen Canyon Dam for the next 20 years.

The plan calls for a more even monthly water release pattern from the dam and a continuation of the high-flow releases aimed at washing sand from tributaries into the mainstem of the Colorado River to build up sandbars.

It also allows for the mechanical removal of trout near the Little Colorado River confluence and experimentation with various water release patterns aimed at limiting juvenile trout populations, improving aquatic insect production and creating warmer waters downstream to benefit native chub.

The action chosen by the agency “ensures Glen Canyon Dam will continue to meet its purposes while improving downstream resources and recreational experiences,” the Bureau of Reclamation stated in a press release on Friday.

It said the plan has received letters of support from the seven Colorado Basin states, the National Parks Conservation Association, the Western Area Power Administration and the Navajo Nation.

Representatives with Save the Colorado and Sierra Club, however, said dam managers failed to analyze flow regimes they say would do more to benefit vegetation and aquatic life downstream, didn’t fully analyze methane emissions from Lake Powell and chose a plan that won’t put endangered species on track to full recovery.

“Basically the Park Service and the Bureau of Reclamation did not try to find an alternative that would improve the floodplains, the vegetation or improve the ability for the Colorado River to be a living river. They have surrendered to the fact that the river is declining and they will do their best to slow that decline,” said Alicyn Gitlin, with the Sierra Club’s Grand Canyon Chapter.

In previous comments to the Bureau of Reclamation, the Sierra Club asked the agency to analyze other proposals for Glen Canyon Dam operations, including one to consolidate much of the water from both reservoirs in Lake Mead and another to adjust dam releases to mimic the Colorado River’s historic flows. Making river levels peak in June and then decline between September and February, as they would have pre-dam, would better align flows with the times when plants are releasing their seeds or fish are laying their eggs, Gitlin said.

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But in its response to comments, the agency said such alternatives wouldn’t allow compliance with water delivery requirements and other federal regulations, including the 1992 Grand Canyon Protection Act. Bureau of Reclamation officials who worked on the dam management plan were not able to respond to requests for further comment on Friday afternoon.

The agency said in addition to meeting obligations for water delivery and hydroelectric power generation, its plans for water releases from Lake Powell are expected to improve conditions for humpback chub, trout, and aquatic insects eaten by fish and other animals.

Gitlin countered that the agency’s report also notes several places where the management plan won’t improve the downstream ecosystem. The overall extent of riparian area in Grand Canyon is expected to continue to decrease as are “key native species” in those areas, while river conditions will continue to be poor for native humpback chub, the report said.

The recovery of native fish species as well as the methane emissions attributable to Lake Powell were a concern for the Colorado-based nonprofit Save the Colorado, Executive Director Gary Wockner said.

He cited an October study that found manmade reservoirs contribute about a billion tons of annual carbon dioxide equivalents to the atmosphere, which is about 1.3 percent all greenhouse gases produced by humans.

“Bureau of Reclamation admits (the emissions) exist but is not accounting for them in its environmental impact of the project,” he said.

In its response to comments, the agency did acknowledge that Lake Powell and Lake Mead would be expected to produce greenhouse gas emissions at levels similar to other reservoirs in the semiarid western United States but said those emissions aren’t anticipated to vary among the alternatives it analyzed.

Gitlin and Wockner said their organizations are still considering how to respond to the Bureau of Reclamation’s final plan and evaluating whether they will file comments against it. A final record of decision is expected to be issued after a minimum 30-day public review period.

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Emery Cowan can be reached at (928) 556-2250 or ecowan@azdailysun.com

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Environment, Health and Science Reporter

Emery Cowan writes about science, health and the environment for the Arizona Daily Sun, covering everything from forest restoration to endangered species recovery efforts.

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