Humanity got its first large-scale electricity thanks to hydropower. On Aug. 26, 1895, water flowing over Niagara Falls was diverted to spin two generators, producing electricity to manufacture aluminum and carborundum. Since then, millions of dams have been built worldwide, transforming the energy of moving water into the energy of moving electrons. When we need it, the water spins magnets past a coil of copper wire to give us heat, light and entertainment.

The basics of hydropower haven’t changed much in 120 years. But now scientists and engineers are taking a fresh look at hydropower to try to make it more environmentally friendly.

That’s because, while hydro provides 85 percent of the world’s renewable electricity, it comes with a cost. Along with more commonly known issues such as habitat disruption, recent studies suggest reservoirs created by hydroelectric dams are a significant source of greenhouse gas emissions.

The U.S. Department of Energy is among those working to make hydropower better for the environment.

“Not only DOE, but really the entire hydro industry has agreed that more work needs to be done,” says Hoyt Battey, manager of market acceleration and deployment for the agency’s Wind and Water Power Technologies Office. “Hydro is going to continue to grow and has a lot of future opportunity that most people just aren’t aware of.”

Current global hydropower production is estimated at 1,700 gigawatts, providing about 2 percent of total electric generating capacity.

In the U.S. — where in 2014 hydropower provided a little more than 6 percent of total electricity generation and made up about 48 percent of renewable generation, according to the DOE — hydropower capacity grew by 1.5 GW in the decade prior to 2015, reaching a total of 100 GW, according to the Energy Information Administration. (Wind, solar and natural gas capacity grew faster, while coal and oil declined and nuclear was essentially flat.)

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