Geoscience Reference
In-Depth Information
Although the twentieth-century era of extensive dam construction (the
“hydraulic era,” as discussed in chapter 12) essentially came to an end in the
1970s with the rise of the environmental movement, residents of the West
will have to contend with the risk of dam failures in the future because aging
dams are increasingly stressed by the changing hydrology of the West. As the
climate warms, more precipitation will fall as rain and less as snow, and this
means more runof during the winter and more pressure on the reservoirs.
Most of the region's dams were built more than half a century ago—and
some are considered disasters waiting to happen. For instance, Glen Canyon
Dam on the Colorado River, located on the Arizona-Utah border, began
to show signs that its foundation was deteriorating in June 1983. h is proj-
ect had been controversial when it was built in 1956. h e resulting reservoir
submerged 186 miles of magnii cent canyon lands in northern Arizona and
southern Utah, including over a hundred side canyons and over two thou-
sand Ancestral Pueblo archaeological sites. At er the wet El Niño winter
of 1983, unusually large amounts of meltwater entered the reservoir from
the watershed. h e excess water that poured through the overl ow spillways
began to turn red, indicating that the spillways were beginning to erode
the red sandstone bedrock that supported the dam. James Powell vividly
described the unfolding disaster in his topic
Dead Pool: Lake Powell, Global
Warming, and the Future of Water in the West:
Leaks sprang from joints in the outlet works. High pressure popped up
manhole covers all over the dam, as if a master magician had levitated them.
Everything leaked that could. h e water rumbling through the spillways and
the vibrating dam produced a cacophony of sound. Standing in the access
tunnels in the dam abutments was like being inside a factory in a rainstorm,
as the enormous pressure forced water through the porous sandstone. h ose
approaching the dam from downstream could hear the noise from four miles
away. At two miles, large waves stirred the surface of the river and a violent
rainstorm fell from the mist emitted from the spillways. Springs spurted
from the sandstone walls of Glen Canyon. Closer to the dam the jets from
the spillways began to eat into the protective apron that led back to the base
of the dam where the generator releases emerge. To one making the trip
upstream, that the largest dam disaster in human history might be under way
did not seem far-fetched. (p. 14)
Fortunately, the dam remained standing. According to Powell, its col-
lapse would have resulted in a 580-foot wall of water travelling 300 miles
downstream, destroying Hoover Dam and Lake Mead, primary sources of
