Re-opening Glen Canyon's floodgates

Six years after an experimental flood, enviros want more

  • Humpback chub

    Colorado Division of Wildlife

FLAGSTAFF, Ariz. - The Colorado River was once a warm, muddy red river with flows that would seem of furious proportions today. But Glen Canyon Dam, built in 1963, acts as a giant strainer, starving the river of the sediment crucial to its native ecosystem and allowing only cold, clear water down the river. Beginning in the early 1980s, environmentalists raised the alarm that river flows managed primarily for power production - torrential in the mornings when power customers turned on their lights, and ratcheted down to a trickle at night - were affecting natural resources downstream in Grand Canyon National Park.

In 1992, environmental groups led by the Flagstaff-based Grand Canyon Trust pushed through Congress the Grand Canyon Protection Act, which ordered the Interior Secretary to operate the dam to "protect, mitigate adverse impacts to, and improve" the natural and cultural resources downstream. Four years later, scientists conducted a highly publicized, one-week spike flood of more than 40,000 cubic-feet per second * roughly five times the typical flows.

The goal was to restore the river's native ecosystem by replenishing silt-starved beaches and creating habitat for the Colorado's native fish, especially a rapidly declining population of endangered humpback chub. The small, bottom-feeding fish have lived exclusively in the Colorado in Grand Canyon for 2 million years, and have come to represent the Colorado's imperiled wild history (HCN, 4/15/96: Stirring things up on the Colorado River). The 1996 flood was publicized throughout the nation as a return, however brief, to near-natural conditions in the Colorado.

In the six years since, however, conditions have deteriorated. Slowly, sand deposited high on the river's banks has washed away, and numbers of humpback chub have continued to plummet.

"That river's become a death zone for native fish," says the Grand Canyon Trust's Nikolai Ramsey.

Now, with lessons learned from that effort and new data from ongoing monitoring projects, the collaborative group that advises Interior Secretary Gale Norton on the operation of Glen Canyon Dam is calling for another flood - this time with a better shot at restoring the Colorado's beaches and boosting its native fish.

Resetting the clock

In the pre-dam Canyon, flows ranged from a languid 1,000 cubic-feet per second in winter to silt-laden, chocolate-colored torrents of 100,000 cfs or more in the spring. Pre-dam water temperatures varied just as widely, from near freezing into the 80s during the summer. Today, flows are much less variable, typically ranging from 5,000 cfs up to the 20s. Water pours from the dam at a steady 48 degrees. Scientists liken the river's static conditions now to a ponderosa pine forest deprived of its natural fire cycle.

"You need these floods in a river system to keep setting the clock," says Matt Kaplinski, a Northern Arizona University geologist who studies the river's beaches. "(The dam took) out a disturbance event from the whole system."

Without periodic high flows to knock them back, non-native tamarisk trees have gained a foothold on the riverbanks. Native fish have suffered because of the unnaturally clear, cold water, while introduced game fish populations - trout, catfish, minnows and carp - have thrived. Hundreds of thousands of rainbow trout introduced by the Arizona Game and Fish Department in the 1990s are overwhelming the system's resources and may be outcompeting - even preying on - native fish like the humpback chub. Numbers of the native chub, once in the millions, are estimated to be less than 2,000.

The 1996 flood was an attempt to bring the river closer to its natural state by mimicking pre-dam high flows and sediment patterns. But Steve Gloss, a scientist with the U.S. Geological Survey's Grand Canyon Monitoring and Research Center (GCMRC), who helped author the new flood plan, concedes that the 1996 flood came up short. Essentially, it moved sediment from beach to beach rather than from the river channel onto the beaches.

According to the new flood proposal, flows through Glen Canyon Dam will be kept low through the winter so that, as monsoonal rains wash sediment into the Colorado from two tributaries just below the dam, the silt will be retained in the main river channel. Next January, a two-day peak flood will wash the accumulated sediment out of the river's channel and onto its banks.

The additional sand will protect archaeological resources that are threatened by erosion, as well as improve beach conditions for boaters and other recreationists. More importantly, scientists hope the sediment will create eddies, recreating the wilder kind of river to which the humpback chub are adapted. Three months of fluctuating flows following the January peak have been designed to further help chub by disrupting the shoreline habitat favored by juvenile trout.

Power play

The Glen Canyon Dam Adaptive Management Work Group (AMWG) is a 25-member consortium (including the Bureau of Reclamation, tribal government groups, power and recreation industries, environmental groups and scientists) that makes recommendations to the Interior secretary about dam operations. At the group's April meeting, 24 of the members agreed to another flood. It was opposed only by the representative from Colorado's Water Conservation Board.

That plan, which now awaits Interior Secretary Norton's approval, involved a compromise on the proposed timing of the spike flow. The Grand Canyon Trust, with support from the Flagstaff-based group Southwest Rivers, pushed for a flood immediately following sediment input from summer monsoons. But that would have usurped a deal Bruce Babbitt made with the power industry back in 1996, limiting flood flows to times when they could be justified for dam safety reasons. That's typically January through July, when lake levels sometimes get so high that it makes sense to spill water in excess of the roughly 30,000 cfs limit for power generation.

The concession for a January flood won the support of the Western Area Power Administration, which markets power from the dam. Clayton Palmer, manager of resource and environmental planning for WAPA's Colorado River office, says that even though power production will be cut back through December while sediment is sequestered in the river channel, the two-day spike flood in January will have a minimal impact on revenues. Furthermore, the high, fluctuating flows for the three months following the spike can be timed to coincide with power demand - resulting in a slight profit boost.

To some environmentalists, the compromise goes too far. Southwest Rivers' executive director Pam Hyde split with the Grand Canyon Trust after it agreed to the plan. She says it's nothing more than a "baby step" toward restoring the Grand Canyon's resources, and "politically contaminated" by the desires of the power industry. Other groups, including the Moab, Utah-based activist group Living Rivers, say nothing less than decommissioning the dam will do. On June 17, members of the group, dressed as humpback chub and driving a dump truck filled with a ton of silt, crashed the Bureau of Reclamation's 100th anniversary celebration at Hoover Dam to publicize the impact of dams on river ecosystems.

And even as the proposal awaits Secretary Norton's decision - expected by mid-July - the Grand Canyon Trust itself says that although the flood plan is a good start, much more is needed to restore the equilibrium of the native ecosystem. That may include spilling water from the top of the dam, where it's warmer, and piping sediment into the river from behind the dam. And making that happen may take more than just cooperation within the working group.

"The Interior secretary has a legal obligation to do all that she can using dam operations and other activities to improve the resources in the park," says the Trust's Nikolai Ramsey. "It may take a lawsuit to get where we need to go."

Anne Minard is a freelance writer based in Flagstaff, Arizona.


  • Grand Canyon Monitoring and Research Center, 928/556-7094,;
  • Grand Canyon Trust, 928/774-7488,;
  • Living Rivers, 435/259-1063,

Copyright © 2002 HCN and Anne Minard

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