COLORADO RIVER

Glen Canyon Dam test flow raises questions about future management

April Reese, Land Letter Southwest reporter

GLEN CANYON DAM, ARIZ. -- Eight years after an experimental flood aimed
at boosting the faltering ecosystem in Grand Canyon National Park, dam
operators have opened the bypass tubes once again. But whether or not
the experiment fares better than its failed predecessor, Grand Canyon
stewards say it will undoubtedly raise difficult questions about how the dam
should be managed in the future.

Beginning Nov. 21, the Bureau of Reclamation, which operates Glen
Canyon Dam, unleashed 224,000 acre-feet of water through four giant bypass
tubes over 90 hours. Scientists and dam managers hope the high flows, rushing
down the canyon at 41,000 cubic feet per second (cfs), will stir up
sediment flowing in from tributaries downstream from the dam and
deposit sand in the Grand Canyon's river channel, building beaches and sandbars
to help endangered fish and provide camping areas for rafting expeditions.

"This is amazing," said Sam Spiller, lower Colorado River coordinator
with the Fish and Wildlife Service, watching cylindrical torrents of water
blast through four bypass tubes at the base of the dam. "Even during a
drought season, we're going to go ahead and take advantage of the
sediment." Bureau of Reclamation scientists and engineers began a three-day
release of water from Lake Powell through Glen Canyon Dam Nov. 21 in an effort
to move 1 million tons of sand and silt downstream to restore sandbars,
beaches and habitat for native species along the Grand Canyon's
Colorado River. Photo by April Reese.

The experiment was initially scheduled for January, but dam managers
decided to release the high flows in November to capitalize on recent
storms that have swelled the Colorado River's tributaries with sediment
in recent weeks.

"The sediments have come down from these storm events," Spiller said.
"The question is, can we put these sediments up [on the banks] and restore
some of our beach habitat?"

The deposition of sediment creates pools and ripples that provide
important habitat for the humpback chub, one of four endangered fish
that persist in the Colorado River, and encourage willow growth, which
supports southwestern willow flycatchers, an endangered bird.

"The sediment, sand, mud and silt play an important role in the
ecosystem," said Chip Groat, director of the U.S. Geological Survey.

An earlier 45,000 cfs test flow in 1996 failed to keep deposited
sediment in the system long enough to benefit the ecosystem, largely because the
release was too long, eventually scouring the beaches and sandbars it
had built, scientists said.

"If there's too much [water], the sediment just erodes -- it goes down
to Lake Mead," said Denny Fenn, director of the Geological Survey's
Southwest Biological Science Center.

The test flow was the result of a proposal from the Glen Canyon Dam
Adaptive Management Work Group, which makes recommendations on dam
management and protection of downstream resources, as required under
the Grand Canyon Protection Act. The group is comprised of hydropower
interests, environmentalists, Park Service officials and other
stakeholders.

The release dropped the level of Lake Powell, now down to about 375
feet, by 2-and-a-half feet. But the water sent downstream will go to meet
delivery obligations under the Colorado River Compact, which divvies up
the river's water among seven western states. Releases from the dam
will be lowered in the coming months to offset the high flows sent
downstream during the experiment, Bureau of Reclamation officials said.

The Western Area Power Administration, which generates power from the
dam, estimates that it lost almost $2 million during the test flow, which
bypassed water around the power plant. But the loss of power generation
will be made up for during fluctuating flows over the next few months,
said Clayton Palmer, who represents WAPA in the working group.

While the long-term effect of the experiment will not be known for at
least a year, preliminary measurements suggest the flows have deposited
sediment onto beaches and sandbars. But it remains to be seen whether
enough sediment has been loaded into the river to offset the constant
erosion that occurs during normal releases from the dam, said Scott
Wright, a hydrologist with the Grand Canyon Monitoring and Research
Center.

"What we've seen in the past is there's consistent erosion of sand in
the canyon under normal power plant operations," he said. "The question is
whether ... we can overcome the erosion that happens during regular
plant operations."

Scientists are taking a trip down the river this week to examine the
new sandbars, he said. "I think they will be there, but there's also a
question of how long the sandbars will last." Monitoring will continue
over the next year and a half.
A changed ecosystem These before-and-after photos show how the experimental flood has
expanded a sandbar. Photo courtesy of Arizona State University/Mark Schmeeckle.

Even if the test flow proves to be a long-term success, the Grand
Canyon ecosystem faces a myriad of other problems, scientists note. The water
in the river is cooler than it was historically, because most of the water
that flows downstream has languished in the deep, cool reservoir behind
the dam before being released. And while dam managers have altered
flows to help the ecosystem, the river no longer rages and whimpers the way
it did historically (Land Letter, Dec. 11, 2003).

Those changes, along with the invasion of exotic fish, are largely
responsible for the extinction of four species of native fish and for
the endangered status of the four remaining native fish species in the
Grand Canyon, including the humpback chub (Land Letter, Oct. 30, 2003).

Today, the Colorado River, named for its historic reddish hue, is a
very different river. "It's clear, it's cold, it's got a lot of trout, which
compete with the native fish, and the flow regime is drastically
different from what it used to be," Wright said.

And while the test flow may have helped carry sediment loaded into the
river by its major tributaries, most of the sand that would flow
downstream is trapped by the dam. Managers estimate that 92 percent of
the sediment that would be carried downstream by an undammed river is
settling behind Glen Canyon Dam -- a growing underwater sandbox that also limits
water storage capacity.

Some environmental groups question whether such experiments will be
enough to recover the ecosystem in the Grand Canyon.

"The proposed habitat-building experiment is unlikely to materialize
any benefits due to general lack of sediment in the system," wrote John
Weisheit of Living Rivers in a letter to dam managers. "Even if such
sediment were available, it would not be distributed in a timeframe to
benefit the humpback chub."

But Nikolai Ramsey, who represents Grand Canyon Trust in the working
group, said he hopes the test flow will have a positive ecological
effect. "This experiment is a watershed event," Ramsey said. "It's possible
that many resources will benefit -- so much is tied to sediment."
What next?

If the test flow is effective, such flows would need to be replicated
on a regular basis to help the ecosystem recover over the long-term,
scientists say. But working group members disagree on whether the law allows for
regular bypasses of the power plant. WAPA believes it does not;
environmental groups insist that it does.

"The issue is, can you conduct those kind of flows on a regular basis
and conform to the law?" Palmer asked. "The 1968 Colorado River Basin Act
doesn't allow bypasses of the power plant, unless it's hydrologically
necessary. ... That is going to be a problem. So we're not advocating
at this point that [high flows] be conducted on a regular basis."

But if the test flow demonstrates that regular high flows are what the
ecosystem needs, managers should adjust dam management accordingly,
Ramsey argued. "If this experiment works, why shouldn't we do this every
year?" he asked.

On the other hand, if the experiment fails, managers are left with
another difficult dilemma.

"During the eight years of adaptive management, we tried various
things, and the resources continued to decline," Ramsey said. "If this doesn't
work, it's going to be highly suggestive that the Grand Canyon
resources will not be able to be restored to any kind of health with the dam
still there. So if this experiment doesn't work, what do we have left?"

There is at least one option that has not yet been tried. Dam managers
have suggested building a sediment slurry pipeline that would deliver
sediment from behind the dam into the river on the other side. But some
working group members contend that would be expensive and may not work.
Scientists are currently doing a feasibility study on the pipeline
proposal.

Another option might be to try the high test flow again when more
sediment is coming into the Colorado River from its tributaries, Wright said.

"What's left are very difficult and expensive alternatives," Palmer
said.

One solution the working group will not discuss, Ramsey said, is
decommissioning the dam, an option that Living Rivers and a handful of
other groups have been pushing for several years. The working group's
approach has been to restore the Grand Canyon's resources to the
greatest extent possible while maintaining the human benefits from the dam. But
with little left to try, that unacknowledged "gorilla in the room" may
become increasingly difficult to ignore, Ramsey said.

"The dam has generated significant benefits, but if its existence is
tied to the Grand Canyon's demise, well it's just not worth it," he said.
"If we learn that there's nothing we can do, I think we'll inevitably be on
the side that we'll have to look at removing the dam. Those are strong
words, but I think this experiment will have those kinds of
implications for a lot of us."