According to Thomas J. Feeley's 2004 report "Responding to Emerging Power Plant-Water Issues," about 25 gallons of water are needed for each kilowatt-hour of electricity (http://www.leonardo-energy.org/drupal/node/1719). Nuclear power plants use about 9% less than coal-fired power plants (ibid), but still . . . all that water just to turn on lights, the computer, the heater/ac . . . !
As per other types of energy production . . . wind turbine generation "uses less than 1/600 as much water per unit of electricity produced as does nuclear, and approximately 1/500 as much as coal" (http://www.awea.org/faq/water.html).
Still . . . still there is an alternative that does not depend on water or fossil fuels, thus freeing up water for other uses and keeping the air free of carbon emissions. For more information, please see www.terrahumanafoundation.org.