Hydropower conjures images of massive, landscape-shattering dams, such as the Three Gorges on upper tributaries of the Yangtze River in China. Large hydroelectric dams produce enormous amounts of electricity, but they also swallow up vast swaths of natural and human habitat. They impact water movement and quality, sediment patterns, and fish migration.
Smaller in-stream turbines are different. Placed within a free-flowing river or stream, they capture water’s kinetic energy without creating a reservoir and its repercussions. The underwater analogue to wind turbines, their blades rotate as water moves past, generating relatively continuous electricity. No barriers, diversions, or storage are required, only limited structural support. No emissions ensue.
In remote communities from Alaska to Nepal, this technology is expanding electrification and replacing expensive and dirty diesel generators. In urban environments, in-stream turbines can be placed within city water mains (called conduit hydropower).
As in-stream hydro grows, it is important to note that not all “run-of-river” projects actually let the river run. Some have diverted waterways, caused floods, and impeded fish migration. Careful design and installation can ensure clean energy that is also ecologically sound.
Three Gorges…displaced 1.2 million people: Watts, Jonathan. “Three Gorges Dam May Force Relocation of a Further 300,000 People.” The Guardian. January 22, 2010.
native communities in rural Alaska: Mooney, Chris. “Alaska’s Quest to Power Remote Villages—and How It Could Spread Clean Energy Worldwide.” Washington Post. August 14, 2015.
Waterways fed by Himalayan snowmelt: Lee, Amy. “Microhydro Drives Change in Rural Nepal.” New York Times. June 20, 2012
city water mains; Portland, Oregon: Profita, Cassandra. “Portland Now Generating Hydropower In Its Water Pipes.” Oregon Public Broadcasting. January 20, 2015; Slavin, Terry. “From Oregon to Johannesburg, Micro-Hydro Offers Solution to Drought Hit Cities.” The Guardian. September 18, 2015.
[potential of] U.S. hydrokinetic resources: National Research Council. An Evaluation of the U.S. Department of Energy’s Marine and Hydrokinetic Resource Assessments. Washington, D.C.: National Academies Press, 2013.
Correction: If in-stream hydro grows to supply 3.7 percent of the world’s electricity by 2050, it can reduce 4 gigatons of carbon dioxide emissions and save $568.4 billion in energy costs.