The Union of Concerned Scientists describes the various roles of water in the process of producing electricity from fuel extraction, production, refining, processing, and transport to electricity generation and emissions control at the power plant. When comparing energy sources, one thing to keep in mind is the amount of water required for the entire life cycle of each energy source.
For example, I recently learned that natural gas requires the least amount of water to produce electricity when you consider the amount of water needed to produce 1000 kilowatt-hours of electricity. This 2008 article from the Institute of Electrical and Electronics Engineers, How much Water does it take to make electricity, summarizes research that took place at the Virginia Water Resources Research Center, to quantify the amount of water consumed during the production of a dozen types of fuel. To learn more, visit the original publication here.
Waterfootprint.org has also calculated the water footprint for various renewable and on-renewable energy sources, concluding that “the water footprint of energy from biomass is 70 to 400 times larger than the water footprint of the other primary energy carriers (excluding hydropower).”