“Who would have guessed that instead of Arizona vs. California, we may have South Carolina vs. Georgia?” Graf said. “The looming issue of providing enough water for Atlanta and the possibility of reaching to the Savannah River for water for Atlanta is an example of the coming debates over our region’s water.”
For water supply to be considered sustainable, the researchers calculated that no more than 40 percent of freshwater resources should be appropriated for human use, to accommodate flow variability, navigation, recreation and ecosystem health.
They also determined how much water each region of the United States needs to meet all its municipal, agricultural and industrial demands and compared the need to the amount of fresh water in streams and rivers. The assessments did not include groundwater resources.
The researchers found that neither the Southwest nor the Southeast have enough water to meet their needs. With the exception of Florida, Southeastern states have their largest cities in interior, piedmont locations where water-storage reservoirs and watersheds are increasingly unable to supply enough water for agriculture, industry and municipal uses, said biologist and co-author Dr. John Sabo of Arizona State University.
While there are more reservoirs in the East, they are smaller than their Western counterparts, Graf said. These smaller reservoirs are more susceptible to evaporation losses than larger ones. Most of these smaller reservoirs in the Southeast are designed to capture precipitation that falls within a year, so changes in precipitation rapidly influence reservoir water levels.
“The recent droughts in the Southeast during the summers of 2002, 2005 and 2007 indicate severe water shortages due to very low rainfall, and water supply is dependent upon precipitation, which is likely to be more uncertain in the near future,” Sinha said.
In addition, the fragmentation of river networks because of dams threatens biodiversity in the Southeast, one of the most diverse ecosystems in North America, Kominoski said.