Page 28 - aruba-today-20170225

A28 SCIENCE
Saturday 25 February 2017

Study: Global warming is shrinking river vital to 40M people

DAN ELLIOTT much of the Colorado Riv-
Associated Press er’s water ranged from 120
DENVER (AP) — Global to 216 percent of normal
warming is already shrink- Thursday. For their study,
ing the Colorado River, the Udall and Overpeck ana-
most important waterway lyzed temperature, precip-
in the American Southwest, itation and water volume
and it could reduce the in the basin from 2000 to
flow by more than a third 2014 and compared it with
by the end of the century, historical data, including a
two scientists say. 1953-1967 drought. Tem-
The river’s volume has perature and precipitation
dropped more than 19 per- records date to 1896 and
cent during a drought grip- river flow records to 1906.
ping the region since 2000, Temperatures in the 2000-
and a shortage of rain and 2014 period were a record
snow can account for only 1.6 degrees Fahrenheit
about two-thirds of that above the historical aver-
decline, according to hy- age, while precipitation
drology researchers Brad was about 4.6 percent be-
Udall of Colorado State low, they said.
University and Jonathan Using existing climate
Overpeck of the University models, the researchers
of Arizona. In this April 16, 2013 file photo, a “bathtub ring” marks the high water mark as a recreational boat said that much decline in
In a study published last approaches Hoover Dam along Black Canyon on Lake Mead, the largest Colorado River reser- precipitation should have
week in the journal Water voir, near Boulder City, Nev. produced a reduction of
Resources Research, they Associated Press about 11.4 percent in the
concluded that the rest river flow, not the 19.3 per-
of the decline is due to a means. 40 million people and 6,300 already overtaxed. Wa- cent that occurred.
warming atmosphere in- Their projections could sig- square miles of farmland. ter storage at Mead was They concluded that the
duced by climate change, nal big problems for cit- “Fifteen years into the 21st at 42 percent of capacity rest was due to higher
which is drawing more ies and farmers across the century, the emerging real- Wednesday, and Powell temperatures, which in-
moisture out of the Colora- 246,000-square-mile basin, ity is that climate change was at 46 percent. creased evaporation from
do River Basin’s waterways, which spans parts of seven is already depleting the Water managers have water and soil, sucked
snowbanks, plants and soil states and Mexico. The riv- Colorado River water sup- said that Mead could drop more moisture from snow
by evaporation and other er supplies water to about plies at the upper end of low enough to trigger cuts and sent more water from
the range suggested by next year in water deliver- plant leaves into the atmo-
previously published pro- ies to Arizona and Nevada, sphere. Martin Hoerling, a
jections,” the research- which would be the first meteorologist at the Na-
ers wrote. “Record-setting states affected by short- tional Oceanic and Atmo-
temperatures are an im- ages under the multistate spheric Administration who
portant and underappre- agreements and rules gov- was not involved in the
ciated component of the erning the system. study, questioned whether
flow reductions now being But heavy snow in the West the temperature rise from
observed.” this winter may keep the 2000 to 2014 was entirely
The Colorado River and its cuts at bay. Snowpack in due to global warming.
two major reservoirs, Lake the Wyoming and Colora- Some was likely caused by
Mead and Lake Powell, are do mountains that provide drought, he said.q