It’s fun in the sun as usual
at Lake Powell, as this summer follows another in a pattern of
drought in the 21st century. But though the reservoir has plenty of
water for boating, its primary purpose is to store water for the
American Southwest. By that criterion, Lake Powell is a bust at 52
percent of capacity.
Hopes for more storage were high
only six months ago. Storms in Colorado early last winter left
record snowfalls, and it looked to be an average or even better
year across the Colorado River Basin. But winter retired early, as
has become its habit, and runoff was again substandard, at only 75
percent of average.
Aridity in the Southwest has always
been axiomatic, nearly a point of pride. It’s how we define the
region and, by extension, ourselves. Even so, fresh evidence
continues to arrive that forces us to redefine our aridity.
The most recent testimony is a study of tree rings in the
river basin, and it reveals that extended droughts were far more
common in the past. For example, various claims have been made in
recent years that our current drought is the worst in hundreds of
years. In fact, according to tree rings at Lees Ferry, at the mouth
of the Grand Canyon, the annual flow of the river during 1844-1848
was lower than the observed flow of 1999-2004.
Trees also
tell of many extended droughts. Eight periods between 1536 and 1850
may have been as dry as the recent drought, according to the work
by Western climate specialists Connie A. Woodhouse, Stephen T.
Gray, and David M. Meko. They also found evidence that droughts of
the past have been longer than the drought of recent years —
perhaps decades long. The tree rings, they said in a report issued
earlier this year, “demonstrate that severe, sustained droughts are
a defining feature of the Upper Colorado River hydroclimate.”
These more severe, sustained droughts of the distant past
are in sharp contrast with the anomalously wet 20th century.
Wettest of the wet was the period from 1910 to 1920, the basis for
the Colorado River Compact of 1922, which apportions the waters
among the seven states of the river basin. Another particularly wet
period came during the 1980s and 1990s. In other words, our
cheerful understanding of aridity in the Southwest has been that of
a glass half-full.
This view into the past is important
given two trends of the present and future. First is the great
population growth under way. By one estimate, the Colorado River
already serves 25 million people, from Cheyenne to San Diego and
from Albuquerque to Salt Lake City. Several Colorado River Basin
states led the nation in population growth during the 1990s, and
that trend is expected to continue.
Global warming is a
second consideration. Computer models are only now being delivered
that pick up the bumpiness of the Rocky Mountains and the Sierra
Nevada. Earlier versions were far too coarse. Increased greenhouse
gas emissions may also change the climate of the West. That said,
all computer modeling predicts shorter winters, earlier runoff and
higher temperatures. That means less snow in the high country
— the source of 80 percent of the water in the West —
and the snow is less likely to linger into summer. That means more
water in low-lying reservoirs where it can evaporate more readily.
Looking both backward aided by tree rings and forward
given both demographic projections and greenhouse gas theory, the
water situation in the West is likely to get much more dicey. On
both counts, we need a revised appreciation for aridity in the
American Southwest.
Meanwhile, Lake Powell has pulled
back from the brink. In early 2005, water managers were fretting
that the reservoir, by then only 33 percent full, would be nearly
empty by now, a bathtub with ugly rings indicating an earlier time
of plenty.
But for many Lake Powell boasters, it’s just
fine as it is. Jim Mullen, a mechanic in Glenwood Springs, Colo.,
visited Powell again in June, and reported a delightful variety of
beaches available due to the lower water level. “When it’s full,
you have no place to camp unless you’re on a house boat,” he said.
“If I never see it fill again, I would be happy.”
For
some, a glass half-full is still as good as it gets.
Allen Best is a contributor to Writers on the Range, a
service of High Country News (hcn.org). He lives
and writes in the Denver area.
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