Today’s worst watershed stresses may become the new normal

Environmental Research Web via the University of Colorado at Boulder: Nearly one in 10 U.S. watersheds is “stressed,” with demand for water exceeding natural supply, according to a new analysis of surface water in the United States. What’s more, the lowest water flow seasons of recent years—times of great stress on rivers, streams, and sectors that use their waters—are likely to become typical as climates continue to warm.

“By midcentury, we expect to see less reliable surface water supplies in several regions of the United States,” said the study’s lead author, Kristen Averyt, associate director for science at the Cooperative Institute for Research in Environmental Sciences (CIRES) at the University of Colorado Boulder. “This is likely to create growing challenges for agriculture, electrical suppliers and municipalities, as there may be more demand for water and less to go around.”

Averyt and her colleagues evaluated supplies and demands on freshwater resources for each of the 2,103 watersheds in the continental United States, using a large suite of existing data sets.

They identified times of extreme water stress between 1999 and 2007, and they estimated future surface water stress—using existing climate projections—for every watershed. In the paper, published online in Environmental Research Letters on Sept. 17, the authors also diagnosed the reasons contributing to stress.

Across the United States, the team found that water supplies are already stressed (i.e., demands for water outstrip natural supplies) in 193 of the 2,103 watersheds examined....

The watershed of the Colorado River, created by  Karl Musser using USGS data, Wikimedia Commons,  Creative Commons Attribution-Share Alike 3.0 Unported license