A fascinating and frightening recent study from the National Resources Defense Council unveiled serious threats to water sustainability in the United States over the coming decades. In an era of rapidly unfolding climate change, the Council’s research found that more than 1,100 counties, or one third of all counties in the lower 48 states, face higher risks of water shortages due to global warming. More than 400 of these “will face extremely high risks of water shortages.”
The study was performed for the NRDC by Tetra Tech, a consulting firm.
According to the study, two main causes for increased shortages are shifts in preciptiation and potential evaportranspiration (PET). In short, many places will get less rain and snow, and greater evaporation. The study also pointed to greater water withdrawals “groundwater, lakes, rivers, streams, and manmade structures . . . are also a primary reason for increasing vulnerability.” The greatest demand on water supplies will come from agriculture, power plant cooling and domestic use.
Furthermore, in many places—Texas, the Southwest, California—water withdrawal is already greater than 100 percent of the available precipitation. In other words, these places are already dependent on either an unsustainable drawdown of aquifers, or on piping from other locations. Because climate change will increase the number of vulnerable areas, it will be harder and harder to pump water from other places.
“This vulnerability,” the report states, “may be most pronounced in regions like Texas and the Great Plains, where changes in precipitation and increases in temperature will mean that projected evapotranspiration will exceed rain and snowfall (precipitation). In these regions there will not be any available precipitation at all.”
Given the importance of the Great Plains to international food production, such a prediction is alarming indeed. According to the EPA, the U.S. produces about 13 percent of the world’s wheat, and about two-thirds of that production comes from the Great Plains.
The report develops a water supply “sustainability index” based on projected water demand and groundwater use as a share of available precipitation, susceptibility to drought and projected increases in withdrawals and summer deficit.
Aside from threats to agriculture, what happens to major populations centers like Phoenix and Las Vegas in the deep red zone? Will they just dry up and blow away?