* Irrigation, drinking water to be affected by 2100
* Driest areas are also some of most heavily populated
* Interior Department calls for conservation, efficiency
By Deborah Zabarenko, Environment Correspondent
WASHINGTON, April 25 Climate change could cut
water flow in some of the American West's biggest river basins
-- including the Rio Grande and the Colorado -- by up to 20
percent this century, the Interior Department reported on
This steep drop in stream flow is projected for parts of
the U.S. West that have seen marked increases in population and
droughts over recent decades, Interior Secretary Ken Salazar
said in a telephone briefing.
"These changes will directly affect the West's water
supplies, which are already stretched in meeting demands for
drinking, irrigating crops, generating electricity and filling
our lakes and aquifers for activities like fishing, boating and
to power our economy," he said.
A new Interior Department report outlines increased risks
to water resources in the U.S. West for the 21st century,
-- a temperature increase of 5-7 degrees F (2.77 to 3.88
-- more precipitation where it's already wet (northwestern
and north-central parts of the American West) and less where
it's already too dry (southwestern and south-central parts);
-- a decrease in April 1st snowpack, a standard benchmark
measurement used to project river basin runoff;
-- an 8 to 20 percent decrease in average annual stream
flow in several river basins, including the Colorado, the Rio
Grande, and the San Joaquin.
CLIMATE CHANGE ADDS TO CHALLENGES
"Climate change will add to the challenges we face, which
will be felt first in the Western United States," said Anne
Castle, the Interior Department's assistant secretary for
science and water. She noted that some of the fastest
population growth has occurred in the driest areas, including
parts of Nevada, Arizona, Utah, Idaho and Texas.
"Water is on the leading edge of climate change, so many of
these basins have already experienced significant ... decreases
to water supply," Castle said.
Water managers in the U.S. West are already emphasizing
water conservation and efficiency, Castle said, adding that
they are increasingly focusing on "the energy-water nexus."
"People are paying greater attention to the water demands
of energy development and recognizing that conservation of
energy can mean conservation of water as well," she said.
Salazar said "alarm bells" about the West's water supplies
were sounding across the U.S. political spectrum, and that he
himself felt the need for an "urgency of planning" to deal with
The eight river basins covered by the report are:
-- the Colorado, which supplies water to Arizona,
California, Colorado, Nevada, New Mexico, Utah and Wyoming;
-- the Columbia, which flows through Washington state and
Oregon, with more than 400 dams that provide hydropower,
irrigation, flood control, stream-flow regulation and water;
-- the Klamath, which flows through Oregon and picks up
water from northern California rivers, providing irrigation for
crops and recreation facilities;
-- the Missouri, the longest U.S. river with a watershed of
more than 500,000 square miles (1.295 million sq km) from
Montana to Missouri;
-- the Rio Grande, which provides irrigation, households
and recreation with water in Colorado, New Mexico, Texas and
parts of Mexico;
-- the Sacramento-San Joaquin, which supplies California's
Central Valley and cities including the San Francisco Bay area;
-- the Truckee, which includes the Lake Tahoe watershed and
the headwaters along the eastern slope of the Sierra Nevada.
The full report and other related documents are available
online at www.usbr.gov/climate/ .
(Editing by Cynthia Osterman)