A recent New York Times article reported the negative impacts of electric cars on water supply.

"It takes a lot of water to produce electricity, both to mine and to process coal and other fuels and to cool power plants. Production of gasoline uses water, too, but in an analysis in the journal Environmental Science and Technology, Carey W. King and Michael E. Webber of the University of Texas found that adding more plug-in vehicles would result in a significant increase in water use because of the additional electricity that would have to be generated. For every mile driven by a gas-powered vehicle that is displaced by one driven by an electric vehicle, the researchers report, about three times as much water is consumed (that is, lost to evaporation) and about 17 times as much is withdrawn (used and returned to its source)." (link to full King & Webber article: http://pubs.acs.org/cgi-bin/sample.cgi/esthag/asap/html/es0716195.html)

It would be interesting to know the impact of the shift to electric cars on regional water supplies versus the impact of climage change and continued use of gasoline cars on regional water supplies. Ultimatly, truly successful plug-in cars need to consider the total impact of the car on the environment and not just a reduction of gasoline use.