"One-third of US counties face increased risk of climate-induced water shortage and drought"
By mid-century climate change will mean a high or extreme risk of water shortages in 14 states, according to a new study commissioned by the Natural Resources Defense Council.
One-third of U.S. counties will face at least some higher risks of water shortages, with 400 counties at extremely high risk, the report by consulting firm Tetra Tech concludes. CAP’s Tom Kenworthy has the story.
The report is based on current water use rates extrapolated for expected growth in demand, and water supply projections based on a set of 16 climate models’ estimates of precipitation and temperature by the year 2050.
In part because so many of the counties at greatest risk have large agricultural economies, the disruptions could be great, said Dan Lashof, who directs NRDC’s climate center. “Water shortages can strangle economic development and agricultural production,” he said. “As a result, cities and states will bear real and significant costs if Congress fails to take the steps necessary to slow down and reverse the warming trend”¦. The only way to truly manage the risks exposed by this report is for Congress to pass meaningful legislation that cuts global warming pollution and allows the U.S. to exercise global leadership on the issue.”
The 14 states cited as most at risk in the report are Arizona, Arkansas, California, Colorado, Florida, Idaho, Kansas, Mississippi, Montana, Nebraska, Nevada, New Mexico, Oklahoma and Texas. Many of the counties at extreme risk are in the Great Plains and Southwest.
– Tom Kenworthy is a Senior Fellow at the Center for American Progress.
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Here are some excerpts from the NRDC news release:
More than 1,100 U.S. counties — a full one-third of all counties in the lower 48 states — now face higher risks of water shortages by mid-century as the result of global warming, and more than 400 of these counties will be at extremely high risk for water shortages, based on estimates from a new report by Tetra Tech for the Natural Resources Defense Council (NRDC).The report uses publicly available water use data across the United States and climate projections from a set of models used in recent Intergovernmental Panel on Climate Change (IPCC) work to evaluate withdrawals related to renewable water supply. The report finds that 14 states face an extreme or high risk to water sustainability, or are likely to see limitations on water availability as demand exceeds supply by 2050. These areas include parts of Arizona, Arkansas, California, Colorado, Florida, Idaho, Kansas, Mississippi, Montana, Nebraska, Nevada, New Mexico, Oklahoma, and Texas. In particular, in the Great Plains and Southwest United States, water sustainability is at extreme risk.
The more than 400 counties identified as being at greatest risk in the report reflects a 14-times increase from previous estimates. For a look at county- and state-specific maps detailing the report findings (including a Google Earth map), go to http://www.nrdc.org/globalWarming/watersustainability/ and http://rd.tetratech.com/climatechange/projects/nrdc_climate.asp.
While detailed modeling of climate change impacts on crop production was beyond the scope of the Tetra Tech analysis, the potential scale of disruption is reflected based on the value of the crops produced in the 1,100 at-risk counties. In 2007, the value of the crops produced in the at-risk counties identified in the report exceeded $105 billion. A separate study compared the Tetra Tech data with county-level crop production data from the U.S. Department of Agriculture; state-specific fact sheets outlining the potential agricultural impacts may be found at http://agcarbonmarkets.com/Science.htm….
Sujoy Roy, principal engineer and lead report author, Tetra Tech, said: “The goal of the analysis is to identify regions where potential stresses, and the need to do something about them, may be the greatest. We used publicly available data on current water withdrawals for different sectors of theeconomy, such as irrigation, cooling for power generation, and municipal supply, and estimated future demands using business-as-usual scenarios of growth. We then compared these future withdrawals to a measure of renewable water supply in 2050, based on a set of 16 global climate model projections of temperature and precipitation, to identify regions that may be stressed by water availability. These future stresses are related to changes in precipitation as well as the likelihood of increased demand in some regions.”
Water withdrawal will grow by 25 percent in many areas of the U.S. including the arid Arizona/New Mexico area, the populated areas in the South Atlantic region, Florida, the Mississippi River basin, and Washington, D.C. and surrounding regions.
Estimated water withdrawal as a percentage of available precipitation is generally less than 5 percent for the majority of the Eastern United States, and less than 30 percent for the majority of the Western United States. But in some arid regions (such as Texas, the Southwest, and California) and agricultural areas, water withdrawal is greater than 100 percent of the available precipitation. In other words, in many places, water is already used in quantities that exceed supply.
A summary of the report and related links are available at http://www.nrdc.org/globalWarming/watersustainability/.