Report indicates climate change to affect Colorado water supply planning

Valley Courier (Colorado): The Colorado Water Conservation Board (CWCB) recently released a report, “Colorado Climate Change: A Synthesis to Support Water Resource Management and Adaptation.” The report focuses on observed trends and projections of temperature, precipitation, snow and runoff.

“This report provides the physical science basis to support Governor Ritter’s Climate Action Plan and state efforts to develop water adaptation plans to respond to changes in climate that cannot be avoided,” said Jennifer Gimbel, Director of the CWCB.

….According to observations cited in the report, Colorado’s temperature has increased about 2° F in the past 30 years. Across the Western U.S., the buildup of greenhouse gases in the atmosphere is responsible for about 1° F of this warming, according to modeling studies, and the remaining increase may be due to natural variation.

Computer models project Colorado’s temperature will warm 2.5° F by 2025 and 4° F by 2050. The implications of this are that typical Colorado summer monthly temperatures will be as warm or warmer than the hottest 10 percent summers, between 1950-1999.

…Although winters warm, high-elevation winter temperatures are projected to remain well below freezing, preserving the bulk of the state’s crucial snow pack, which lies above about 8,000 feet. Observed precipitation variability is high and no consistent precipitation trends have been detected.

Model projections of precipitation show little change in annual average precipitation; however, temperature increases alone will have significant impacts on snow and water resources. Earlier spring melt, increased evaporation, and drier soils will reduce runoff for most of the state’s river basins, with a 5-20 percent loss in the Colorado River Basin by the mid-21st century.

…This report suggests a reduction in total water supply by the mid-21st century. The overwhelming majority of studies agree on those trends. “The population and the environment of Western states depend on water from Colorado’s rivers,” said Brad Udall, director of the Western Water Assessment…..

Horseshoe Bend in the Colorado River in Page, Arizona. Shot by Mila Zinkova, Wikimedia Commons, under the terms of the GNU Free Documentation License, Version 1.2