Scientists, climatologists and energy experts share a growing concern: the need for water in the production of energy, especially in regions that are experiencing serious drought. Generating power - whether it be from fossil fuels or renewable energy sources - requires large amounts of water.
Nearly all forms of energy production use large amounts of water. Coal, which generates nearly 50 percent of the electricity in the U.S., needs water for mining and transport, and to cool and lubricate equipment.
Water is also used to cool fuel rods at nuclear plants and to generate steam to power turbines. The biofuel industry needs water for irrigation, fermentation and the production of ethanol and biodiesel fuels.
Alexander Ochs, director of climate and energy at the Worldwatch Institute, says that adds up to a lot of water.
?Per megawatt hour, coal uses 500 to 1000 gallons of water for the production of just one megawatt hour of electricity," said Ochs. "If we look at all the plants combined in the U.S., all the thermo-electric plants [powered by steam] in the U.S. in 2008 alone, they drew 60 billion to 170 billion gallons of water, per year.?
Without water, most types of energy could not be produced. Even renewable energy, like geothermal and solar, use water to cool equipment and to clean the collector panels.
Those requirements have led California, Massachusetts and several Midwestern states to halt the operations of some power plants.
?Places like the Midwest where water is a very scarce resource already today, a number of power plants have actually been halted, and this is actually true for across the United States," said Ochs.
David Brown directs programs for the National Oceanic and Atmospheric Administration across the southern United States. NOAA collects data on climate patterns. Brown says the drought in the American Southwest, the worst in a century, is prompting changes in the energy industry.
"Energy companies are also being forced to be more efficient in the way they use water, whether it is for electricity production in a coal factory or in the mining of natural resources through the fracking [hydraulic fracturing to extract natural gas] process," said Brown. "These companies are also realizing that water resources are strained and will continue to be strained as the climate continues to warm,?
The NOAA expert says water systems in the American Southwest will be under even greater stress over the next several decades.
The agriculture industry is the prime user of water in the United States, closely followed by energy production.
Experts say competition for water resources - from a growing population, and from the agriculture and energy industries - will require difficult decisions, eventually, by local and national governments.