Arizona's Future Climate: Temps Rising, Water Disappearing

Over the last five decades, water from the Colorado River rarely has reached the delta, which used to feed the Sea of Cortez just south of the border between the U.S. and Mexico. (Photo: Adrille/Wikimedia Commons)
Over the last five decades, water from the Colorado River rarely has reached the delta, which used to feed the Sea of Cortez just south of the border between the U.S. and Mexico. (Photo: Adrille/Wikimedia Commons)

The southwestern United States is facing an increasingly stressful future with unabated population growth, oversubscribed water resources and a hotter and drier climate. This, in a nutshell, was the message delivered by a panel of three environmental experts discussing how climate change is already affecting and will impact the Southwest’s environment during a panel discussion on the University of Arizona campus during the Tucson Festival of Books.

The presenters did leave the audience of almost 250 with some reason for optimism, pointing out that small but committed groups working with nongovernmental organizations and tribal communities plus efforts on behalf of the private sector have started and will continue to make a difference.

Population in the six Southwestern states – Arizona, Nevada, California, Colorado, Utah and New Mexico – is expected to grow from currently 56 million to 94 million by the middle of this century, according to the report Assessment of Climate Change in the Southwest United States, to which three of the UA panelists contributed. At the same time, water from the Colorado River already is over-allocated by about 2 million acre-feet, which is. The panelists pointed to a study by the Bureau of Reclamation, which estimated the gap between projected future demand and supply of Colorado River water to be 3 million acre-feet – more than three quarters of a cubic mile.

"Increasing all this consumption by 50 percent is just not going to work," said Karletta Chief, an assistant professor and assistant specialist in the Department of Soil, Water, and Environmental Science in the UA College of Agriculture and Life Sciences. Chief contributed to the report, furnished under the National Climate Assessment, which is prepared every four years to inform the U.S. president and Congress on the status of climate change research and its impacts.

Panelist Gregg Garfin, an assistant professor and assistant specialist in climate, natural resources and policy in the UA’s School of Natural Resources and the Environment, and the main editor of the report, presented data showing that the annual minimum and maximum temperatures have been increasing across all six Southwestern states and will continue to do so, resulting in a possible increase by 8 degrees Fahrenheit by the year 2099.

"The implication is that somewhere between the middle and the end of the century, Tucson's annual average temperatures will be more like Yuma," Garfin said. "Also, we'll see longer heat waves, more days over 100 degrees, and fewer cool nights, in addition to a decrease in spring precipitation, all under the assumption of continued high greenhouse gas emissions."

Rising temperatures, decreased snowfall and earlier spring snowmelt, combined with episodic droughts, already have shown their impact, as massive swaths of conifer forests have died across the Western U.S., from northern Mexico to Alaska.

"It's a one-two punch of drought and increased temperatures," Garfin said. "It depletes soil moisture, trees are wobbly from drought stress, then insects come in and take down the trees."

Read more from this March 24 UANews article at the link below.

Date released: 
Mar 28 2014
Contact: 
Daniel Stolte