Thirsty Hydro Tops List of Water Use in US Energy Sector

Quinn Van Valer-Campbell
Thursday, September 5, 2013

A US Department of Energy (DOE) report released in July details widespread risks of climate change on the energy sector. Increasing temperatures and a decreasing snowpack will greatly contribute to a lower water supply (which is already becoming a fact of life). Hydropower plants are especially at risk, for three reasons: they rely on water as their primary source of energy; higher temperatures cause them to evaporate more water (thus reducing their ability to produce energy), and they are at greater risk of damage from flooding. 

With climate-induced changes to precipitation and snowmelt, there is more scarcity – and therefore more conflict – for water. According to Sara Reardon’s article in New Scientist, a hydropower plant can use anywhere from 15,000 to 68,000 liters of water per megawatt hour generated. To put this into perspective, a nuclear power plant uses about 2,650 liters per megawatt hour, and coal around 1,900. Rooftop solar and wind turbines use virtually no water. 

Higher temperatures brought on by climate change will increase the rate at which water evaporates from large dam reservoirs. Currently, the amount that evaporates from dam reservoirs alone is more than that consumed by the industrial and domestic sectors combined, according to UNEP.

Less water in rivers means a drop in generating capacities of hydropower plants. According to the DOE report, California’s hydropower output deceased by 38% in the past year alone. In the Southwest, Hoover Dam’s shrinking water levels cut its generating capacity by more than 20%. And drought isn’t just affecting the drier Western part of the country – the Southeast’s Chattahoochee River suffered a drought in 2007 that reduced its flow by 20%; overall, that region saw a 45% drop in hydropower generation.

The United States’ era of dam-building is often put forth by dam proponents in the Global South as a model to emulate. But our growing understanding of the climate vulnerability of large-dam hydropower in the US reflects more current information, and offers important lessons. Forward-looking energy planners must consider these risks in their own context, and aim for no-regrets energy choices that reduce climate vulnerability. 

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