Not Tapped Out

U.S. cities may be less vulnerable to water scarcity than previously thought, according to a study in Water Resources Research.

With more people flocking to cities, ensuring that urban centers have enough water is crucial. Researchers often calculate a region’s water resources based on local, renewable sources such as rivers. But cities also import and store water, which sometimes isn’t taken into account.

To figure out how truly dire the problem was, the study authors assessed water availability for 225 urban areas in the United States with more than 100,000 people. The team included sources such as streams, reservoirs, lakes, and groundwater.

If the researchers looked only at local, renewable sources, 47 percent of U.S. city-dwellers appeared vulnerable to water scarcity. But if the calculation included imported and stored water, that number dropped to 17 percent.

The authors also searched for news reports of water shortages over the last few decades. The method that took storage into account did a better job of identifying vulnerable urban areas that actually suffered water scarcity, the team says.Roberta Kwok | 21 January 2013

Source: Padowski, J.C. and J.W. Jawitz. 2012. Water availability and vulnerability of 225 large cities in the United States. Water Resources Research doi: 10.1029/2012WR012335.

Image © Alexander Kirch |