After agriculture, the energy sector is the largest consumer of water in the US. Freshwater resources are already dwindling due to climate change and current population levels, and that burden is likely to intensify. The Energy Information Administration estimates a 40% increase in energy demand by 2050, when the U.S. population is expected to hit 439 million.
But alternative energies won't necessarily ease this pressure. Recent research indicates that most alternative energies—whether renewables like solar thermal and biofuels, or unconventional sources like oil tar sands—use more water than conventional fossil fuels.
"This is shocking, even for people in the business," said Jennifer Turner, director of the China Environmental Forum at the Woodrow Wilson International Center for Scholars. On September 22, Turner chaired a presentation by Circle of Blue, a nonprofit science organization covering global freshwater issues, in which they presented the findings of their investigative series into the relationship between energy production and water consumption in the U.S.
The report, "Choke Point: U.S." argues there can be no energy security without water, and both must be managed together if the country is to avoid shortages of either resource.
Turner wasn't the only one who was shocked. After the presentation she received many emails from water and energy experts who hadn't known the facts beforehand.
Yet Circle of Blue's findings aren't entirely unexpected. They parallel a pair of reports commissioned by Congress in 2004, only one of which has been made public. Released in 2007, the first study, a report to Congress on the energy-water nexus by Sandia National Labs, laid out the conflicts between energy demand and water availability.
The second, called the "Energy-Water Research and Development Roadmap," is intended to detail solutions and research directions. What those are, however, is unknown, since the final report has yet to be made public by the DOE. (Nearly two dozen drafts of the report have been submitted to the agency by Sandia, the most recent in May 2009.)
In an email to SolveClimate News, a DOE spokesperson said the agency planned to release the report, currently under interagency review, "as soon as possible."
Energy Production Versus Water Consumption
Although the final report is not yet public, its general contents were summarized in a separate March 2007 Sandia National Labs paper.
In 2000, the energy sector withdrew nearly 200 billion gallons of freshwater and seawater per day. That's about half of the country's daily water withdrawals.
Most of the water is used for cooling thermoelectric plants, whether powered by oil and gas, nuclear fuels, biomass or concentrated solar. Only wind and photovoltaic solar plants use virtually no water at all.
At the same time, water resources are dwindling. In the last three decades, water reservoir capacity has increased only a few percent, according to the Sandia report. In contrast, it increased threefold during the dam-building era between 1920 and 1980. More recently, plans to dismantle older dams will decrease surface water storage.
In addition, climate change has led to droughts, decreased runoff and lower river levels, especially in the West, where water is already scarce.
The energy-water relationship also works the other way. States like California rely on faraway water sources, so much of the state's energy is used for the transport of water from reservoir to cities. As the reservoirs dip lower from drought, it will take even more energy to operate the water pumps.
"There are a number of examples (today) where energy and water are conflicting," said Michael Hightower, a co-author of the Sandia National Labs Roadmap report.
Solar plants in California have been stalled or scaled back due to water availability, said Hightower, and a biorefinery in Minnesota could not operate because it was denied a water permit.
Europe is feeling these pressures too. In 2006, heat waves forced France and Spain to cut back or close many nuclear power plants. The plants rely on river water for cooling, but the rivers were so warm that the water was useless.
Options do exist for reducing water in electric power generation, said Hightower. Power plants can use brackish water or wastewater for cooling. Another possibility is to switch to dry cooling, where air, rather than water, is used to cool the plant. The process tends to be more expensive and doesn't work well in hot climates like the Southwest, but northern states might be able to use dry cooling "with very little penalty."
Aside from electrical generation, Hightower was particularly worried about the future of transportation fuels. "To me, the transportation fuel sector (may) be hit the hardest because it has fewer options."
Interest in energy security is pushing the development of domestic alternatives such as oil shales, which are more water-intensive than conventional crude oil.
According to the Sandia paper, it takes about 1.5 gallons of water to produce one gallon of petroleum; oil shale production requires 2 to 3 gallons of water. Moreover, most oil shale deposits are in Wyoming, Colorado and Utah, three states with existing water problems.
Green Isn't Necessarily Blue
Ironically, water and sustainability measures can often clash.
Biofuels produced from irrigated corn use 650 times more water than oil-derived gasoline, according to Circle of Blue's findings. For soybean-based biofuels, that number is around 1,000.
As for carbon sequestration, fossil fuel plants that attempt to bury their CO2 will consume 40%–90% more water.
"(These) clean technologies that are meant to save us from conventional oil (pose) a major threat to water security, and this is a crisis," said Turner. All too often, she added, "the water footprint" is not considered in energy development.
Her remarks echoed the conclusion of the Sandia paper, which called for a major overhaul of current policies: "It may not be possible in many areas of the country to meet the country's growing energy and water needs by following the current U.S. path of largely managing water and energy separately while making small improvements in freshwater supply and small changes in energy and water-use efficiency."