The bottom of a drained carp pond near the cooling towers of the Jänschwalde lignite-fired power plant of in Brandenburg, Germany, on November 30, 2018. Photo: Patrick Pleul/picture alliance via Getty Images

In the U.S., 45% of the water pulled from reservoirs, rivers, oceans and underground aquifers is used to cool thermal (fossil fuel) and nuclear power plants for electricity production. Of that water, 73% is fresh, amounting to significantly more than is used for agricultural irrigation — and that still doesn't include water used in processes like fracking to acquire the fuel in the first place.

Why it matters: Although power plants have made small efficiency improvements, they continue to use enormous amounts of water. As demand grows in cities and on farms, competition for water among humans, agriculture and power plants is becoming more intense, especially in drought-prone regions and large population centers.

Background: Coal, natural gas and nuclear power produce a combined 84% of U.S. electricity at a cost of about 30 trillion gallons of fresh and saline water per year. This intense water usage presents several problems:

  1. Water used for cooling can be lost to evaporation, and the water that's sent back into the environment may be contaminated, or so hot that it harms fish and wildlife.
  2. This consumption can create a localized crisis if a region suffers a prolonged drought. Many cities in the southwest U.S. will face water shortages over the next two decades, as Lubbock, Texas, already has.

Yes, but: In addition to emitting far less carbon than traditional sources, renewable energy uses much less water, with wind turbines and solar panels employing almost
negligible amounts. Fortunately, drought-prone areas also tend to be conducive to solar energy generation.

The bottom line: The growth of renewable energy hasn’t been enough to compensate for increasing water use. As governments and corporations look to reduce their carbon emissions from power production — as Facebook and the state of California announced in August they plan to do — they should not neglect renewable energy's freshwater savings.

Luciano Castillo is the Kenninger Professor of Renewable Energy and Power Systems at Purdue University's School of Mechanical Engineering. Walter Gutierrez is a visiting scholar at the school.

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