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 released by the Natural Resources Defense Council (NRDC).
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.
Tetra Tech (Nasdaq: TTEK) wrote the report, which 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).
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, visit the link below.)
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.
Dan Lashof, director of the Climate Center at NRDC, said: “This analysis shows climate change will take a serious toll on water supplies throughout the country in the coming decades, with over one out of three U.S. counties facing greater risks of water shortages. Water shortages can strangle economic development and agricultural production and affected communities. 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. Water management and climate change adaptation plans will be essential to lessen the impacts, but they cannot be expected to counter the effects of a warming climate. 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.”
Water withdrawal will grow by 25% 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% for the majority of the Eastern United States, and less than 30% 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% of the available precipitation. In other words, in many places, water is already used in quantities that exceed supply.
The Tetra Tech report develops a new water supply sustainability index. The risk to water sustainability is based on the following criteria: (1) projected water demand as a share of available precipitation: (2) groundwater use as a share of projected available precipitation; (3) susceptibility to drought; (4) projected increase in freshwater withdrawals; and (5) projected increase in summer water deficit.
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