The Great Lakes hold 18 percent of the world’s fresh surface water, enough to flood the continental U.S. in 9.5 feet of it. But the seemingly endless resource could still face harm from overuse.
“Even in these areas that are water-rich, there are areas of vulnerability,” said Victoria Pebbles, program director for the Great Lakes Commission. “Excessive water withdrawal and excessive water use can harm our ecological resources.”
Pebbles led a report, Integrating Energy and Water Resources Decision Making in the Great Lakes Basin, which looked at the relationship between energy production and water.
“This is the first time an energy study has been done for the Great Lakes region and looked at water resource impacts,” Pebbles said. “Usually, they look at tradeoffs between cost, reliability and greenhouse gas emissions. Water is usually an afterthought.”
The report was issued by the Great Lakes Commission and put together by businesses, organizations, state officials and scientists.
“Energy experts and natural resource agencies talked to each other and realized there’s a clear connection between how the region generates power and what it means for the water resources in the Great Lakes,” said Dick Munson, senior vice president at Recycled Energy Development and report contributor.
Most of the power plants in the Great Lakes basin are thermoelectric plants, which burn fossil fuels to generate electricity.
Thermoelectric power plants in the basin, most of them coal plants, withdrew, used and returned 25.9 billion gallons of water per day in 2007. They withdrew and didn’t return .4 billion gallons per day.
Using and returning the water sounds less harmful but it’s sometimes returned at a different temperature, which hurts fish.
“A change in temperature is considered pollution under the clean water act,” said Nick Schroeck, executive director of the Great Lakes Environmental Law Center and report contributor. “In the worst case scenario warm water discharges can lead to fish kills, but even in the best circumstances they lead to declines in the fish populations.”
Open-cycle cooling systems, which are used by 62 percent of thermoelectric plants in the Great Lakes basin, take in water, heat it to create steam that turns one or more turbines, then pump it back into the source. These systems can also suck in and kill fish and other organisms.
Closed-cycle cooling systems re-circulate hot water. The warm water is air-cooled and then used to create steam and turn a turbine.
Both systems have their drawbacks. Closed-cycle systems withdraw between 97 and 99 percent less water than open-cycles, but lose between 55 and 63 percent more water to evaporation, according to the report.
Renewable energy, like wind and solar power, requires less water than thermoelectric energy, Schroeck said. Currently, only 3 percent of the region’s power comes from renewable sources.
The team studied Great Lakes watersheds to find their vulnerabilities to temperature changes, water quality stress, water quantity stress and withdrawal at the driest part of the year. Those vulnerabilities determine which sources of power the watersheds can support.
Looking at the impacts of power plants on watersheds instead of large bodies of water can help determine their real influence.
“There may not be a huge impact on Lake Huron, but if you were to put in a coal plant it would have an impact on a smaller watershed,” Schroeck said.
Both power companies and ecosystems benefit from knowing a watershed before building on it.
“Utilities want to make sure they get the best return on their investment,” Schroeck said. “The best way to do that is find a facility with adequate water resources that’s less likely to have environmental impacts, because that can be costly for the company and the environment.”
Pebbles hopes states, provinces and electricity providers will look at what type of power plant each watershed can support. She was surprised to see how little discussion usually occurred before decisions.
“There should be a broader dialogue about the need for new capacity and what type of energy is best supported in that area,” Pebbles said. “It may not be a thermoelectric plant.”
Pebbles and Munson hope the report spurs concern among those using the electricity.
“I think the people in the Great Lakes look out over the lakes and think they don’t have to worry about water because there’s so much there,” Munson said. “The way we structure our energy future will have a huge impact on that resource.