Union of Concerned Scientists/Energy and Water in a Warming World

The first chapter of a new report on the effect of power plants on freshwater systems has the feel of a documentary film. Imagine a camera panning the dessicated Texas landscape as a voice intones statistics from the brutal 2011 drought — a dried-up Brazos River, 80 days of 100-degree-plus temperatures in some locations, and so on.

And then the punch line: “An energy-water collision wasn’t far behind.”

Cut to a close-up: “One plant had to curtail nighttime operations because the drought had reduced the amount of cool water available to bring down the temperature of water discharged from the plant,” the report says. (The Environmental Protection Agency regulates the maximum temperature of such discharges to ensure that aquatic life is not harmed and fish breeding and migration are not impeded.)

You get the idea. The report was prepared by the Union of Concerned Scientists in collaboration with independent experts. It quotes Kent Saathoff, a vice president of the Electric Reliability Council of Texas, who said last month, “If we don’t get any rain between now and next summer, there could be several thousand megawatts of generators that won’t have sufficient cooling water to operate next summer.”

Texas may offer a preview of what happens in a warming world. In 2007, there were blackouts in parts of North Carolina because a drought affected the Catawba River. “The thirst of the region’s power plants became incompatible with what the river had to give,” the report said.



Complicating matters, not enough is known about how much water power plants use and how the discharge affects the local environment, it adds.

Both the water shortage and the lack of information will become more problematic, the researchers write. In the not-too-distant future, they say, a growing population is likely to want more air-conditioning than the electrical grid can supply because there will not be enough water available to cool thermoelectric plants.

Power plants generally work by converting water into steam to turn turbines; the water then has to be cooled before it can re-enter the environment or be used again.

Coal-fired plants alone account for 67 percent of freshwater withdrawals by the power sector and for 65 percent of the water completely consumed by it, the report said. Newer plants include air-cooling or “dry cooling” technologies, but so many plants rely on water-cooling that they accounted for 41 percent of the withdrawals of freshwater in the United States in 2005, according to the United States Geological Survey.

That said, they return a great deal of the water they use, usually to rivers — although in the case of some California plants like Diablo Canyon, the cooling water is taken from and returns to the Pacific Ocean.

Yet some water is inevitably lost to evaporation or otherwise never gets back to the rivers. The map above, from the report’s appendix, indicates which states lose the most water to operate power plants.

Not all plants provide accurate reports to the federal Energy Information Administration, however. The report suggests that “many operators estimated annual use rather than measuring it.”

The report noted that in 2008, more than 100 water-cooled coal and natural gas power plants “reported to the government that they produced millions of megawatt-hours of electricity yet used no water at all.” And “power plant operators have universally ignored rules requiring them to specify groundwater sources used for cooling,” it added.

Until some of the data gaps are remedied, the full effects of power plants on watersheds will remain unknown.

A caption with an earlier version of this post identified one of two states where power plants consume the most water during the cooling process. It is Pennsylvania, not Massachusetts. (The other is Texas.)