Small hydroelectric power plant in Serbia, built in 1900.
Михаило Јовановић via Wikimedia

Museum Hydroelectric power plant ″Under the Town″ in Serbia, built in 1900.

Small Hydropower

Reduce SourcesElectricityShift Production
CO2 Equivalent
Reduced / Sequestered
Billion $US
Net First Cost
(To Implement Solution)
Billion $US
Lifetime Net
Operational Savings
Small hydropower systems capture the energy of free-flowing water, without using a dam. They can replace dirty diesel generators with clean electricity generation.

Solution Summary*

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.

* excerpted from the book, Drawdown

If small hydropower systems grows to supply 994–1,136 terawatt-hours of electricity in 2050 compared with the current levels of around 670 terawatt-hours, it can reduce 1.7–3.3 gigatons of greenhouse gases emissions and save US$315–544 billion in fixed and variable operation and maintenance costs and fuel costs. Communities in remote mountainous areas are among the last regions in need of electrification; small hydropower through for example instream hydro offers them a reliable and cost-effective method of generating electricity.