As our rafts bounced through what was
supposed to be the last rapid on the Colorado River before its
transition to the slack water of Lake Powell, we were surprised to
hear the rumble of whitewater downstream.
The
half-mile-long Imperial Rapid, submerged for three decades, had
re-surfaced. The natural draining of the nation’s second largest
reservoir was under way, but how far would it go, we wondered?
Climate change in the region has lowered the reservoir
120 feet over the past five years. This drop should have been
sufficient to expose half the remaining 21 rapids that were also
submerged by the reservoir, yet only Imperial has come out so far.
A look around from the raft revealed the problem: We were floating
through a massive slab of sediment that had built up in the decades
since Glen Canyon Dam was finished.
The remainder of our
descent was through a ditch framed by gray cliffs of sand rising 25
feet on either side, with dump-truck-sized chunks calving off like
icebergs every 15 minutes or so.
The ditch widened as we
caught up with the slack water of the reservoir, now 30 miles below
Imperial Rapid, but still 140 miles from Glen Canyon Dam. The lower
water levels here, and on the edges of much of the rest of the
reservoir, have re-exposed many of the cliffs, spires and canyon
walls that John Wesley Powell dramatically described on his 1869
exploration of Glen Canyon.
Although Lake Powell
reservoir is just 40 percent full and has lost 50 percent of its
surface area, it has dropped only 20 percent in elevation. The
reservoir is still 445 feet deep near the dam. It’s like a
wide funnel: There’s more water stored at the top. But scientists
predict that it will fall more rapidly if present climatic
conditions persist.
The reservoir’s elevation could also
drop three times faster over the next three years than it has over
the past five. If that happens, it would cause hydroelectric power
production at the dam to cease in 2006. By 2007, a condition known
as “dead pool” would be created, which means that the dam, for all
practical purposes, would become useless as a power generator. The
reservoir, however, would still stretch 104 miles upstream, contain
approximately 2 million acre-feet of water and sediment, and rest
234 feet above the original river bed at Glen Canyon Dam.
Still submerged would be most of Glen Canyon’s 125 signature side
canyons, which inspired the canyon’s pre-dam river runners along
with the mounting numbers of present-day advocates for Glen
Canyon’s restoration. Nature’s crash course in water scarcity is
helping to amplify the mounting economic and environmental
liabilities associated with Glen Canyon Dam and Lake Powell,
raising the prospect of decommissioning the dam and uncovering the
remainder of the canyon.
Glen Canyon Dam was completed in
1963, as a water-storage facility for downstream users. Because of
other storage facilities built in the basin, principally Lake Mead
behind Hoover Dam, it will be this winter before Lake Powell’s
storage will, for the first time, actually contribute to downstream
water use.
Over the years, Lake Powell will have lost 40
million acre-feet of water from evaporation and seepage, while
providing only 23 million acre-feet in storage. This lost water
represents nearly three years of the entire annual flow of the
Colorado River. It’s not surprising that people are looking
for more efficient ways to save this valuable water. California,
Nevada and Arizona are already doing so by storing Colorado River
water in underground aquifers. They lose as little as 1 percent of
the water to the environment, compared to the over 60 percent of
water that is lost at Lake Powell.
Concern is also
mounting over the damage Glen Canyon Dam is causing to the
downstream ecosystem in Grand Canyon National Park. Four of the
Canyon’s eight native fish are already gone, as are otters,
muskrats and a host of birds, insects and reptiles. Despite more
than $200 million invested in efforts to mitigate the dam’s
impacts, biologists say these declines will continue.
As
the drought continues, a growing number of scientists are
questioning whether there will ever be enough water to fill Lake
Powell. But I have a different question: Once the reservoir dies a
natural death, shouldn’t we finish the job and let the river
run again?
John Weisheit is a contributor to
Writers on the Range, a service of High Country News (hcn.org). He
is conservation director for Living Rivers, a nonprofit group in
Moab, Utah.
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