Scientific literature regarding the future of water in the Southwest up to this point has been alarming, yet vague. In general, studies have confirmed that rising temperatures will hit the Southwest hard, with water availability shrinking significantly. Uncertainties related to the degree to which changes will affect evaporation and precipitation have stopped scientists short of making headline-generating predictions.
That changed this week with the release of a new study by researchers at Colorado State University, Princeton, and the U.S. Forest Service that provides rare specifics as to how climate change may affect key reservoirs such as Lake Powell and Lake Mead that feed the Colorado River and therefore the Central Arizona Project (CAP). The study presented a number of varying scenarios dependent upon levels of greenhouse gas emissions and population stresses. One scenario details a dire future in which “Lakes Powell and Mead are projected to drop to zero and only occasionally thereafter add rather small amounts of storage before emptying again.”
“We were surprised to find that climate change is likely to have a much greater effect on future water demands than population growth,” Forest Service research economist Tom Brown, who led the study along with CSU’s Jorge A. Ramirez, told Summit County Citizens Voice. “The combined effects of climate change on water supply and demand could lead to serious water shortages in some regions.”
CAP delivers on average 1.5 million acre-feet of Arizona’s 2.8 million acre-foot Colorado River entitlement each year. Of the annual average delivery, 52 percent of the water is currently used for municipal and industrial purposes (including recharge), 39 percent for agricultural irrigation districts, and 9 percent for Indian communities (Bureau of Reclamation). The study notes that significant water efficiency gains could be found by altering irrigation practices.
With federal and international action on climate change stalled, worst-case scenarios such as the total evaporation of reservoirs like Powell and Mead are increasingly possible. If Central and Southern Arizona are to remain viable in the face of these threats, preparation must begin now with every conservation incentive on the table. Arizona’s farmers, ranchers, golf course operators, and landowners will need time to prepare for a future where water is priced at a level that more accurately reflects its scarcity. Regulators at the Central Arizona Water Conservation District board, Arizona Corporation Commission, and federal departments such as Interior, have their work cut out for them.