>Large quantities of water are needed as well for the production, refining and transport of the fuels that light and heat our homes and buildings, and run our buses and cars.  Every gallon of gasoline at the pump takes about 13 gallons of water to make.

And of course hydroelectric energy requires water to drive the turbines that generate the power.  For every one-foot drop in the level of Lake Mead on the Colorado River, Hoover Dam loses 5-6 megawatts of generating capacity – enough to supply electricity to about 5,000 homes.

In short, energy production is deeply dependent on the availability of water.  And, as a report released last week by the U.S. Department of Energy (DOE) makes clear, as climate change brings hotter temperatures, more widespread and severe droughts, and lower river and lake levels, the nation’s energy supply is becoming more vulnerable. […]

One particularly interesting figure in the report compares the water requirements of seven different types of electric power facilities – nuclear, coal, biopower, natural gas combined-cycle, concentrated solar, photovoltaic solar and wind.  The last two come out as by far the most water-conserving electricity sources.  In contrast to the 20,000-60,000 gallons per megawatt-hour needed for nuclear and coal plants with “once-through” cooling systems, PV solar and wind require only negligible quantities.<

>The report warns that a “business-as-usual” approach would keep emissions within 5 percent of current levels and water withdrawals would not drop significantly until after 2030. And while utilities’ ongoing shift to natural gas would decrease water use in the coming decades, the study says its ongoing requirements could still harm water-strained areas. This shift to natural gas also would do little to lower the power sector’s carbon emissions.

More than 40 percent of US freshwater withdrawals are used for power plant cooling, the report says. These plants also lose several billion gallons of freshwater every day through evaporation.

Further, increasing demand and drought are putting a greater strain on water resources. Low water levels and high water temperatures can cause power plants to cut their electricity output in order to avoid overheating or harming local water bodies. Such energy and water collisions can leave customers with little or no electricity or with added costs because their electric supplier has to purchase power from elsewhere, as occurred during the past two summers.<