Run-of-the-river hydroelectricity

Run-of-the-river hydroelectricity generates electricity from a river’s natural flow with little or no long-term water storage. Its output generally varies with river conditions.

Hydroelectricity: Electricity generated by converting the energy of moving or falling water. Run-of-the-river plants are a hydropower approach that relies on ongoing river flow.
Reservoir hydroelectricity: Hydroelectric generation that stores water in a reservoir for controlled release through turbines. Unlike run-of-the-river plants, reservoir plants can shift generation by releasing stored water.
River discharge: The volume of water flowing past a point in a river per unit of time. Discharge is a key constraint on plant output and changes with weather and season.
Hydrological variability: Changes in water availability and flow over time, including seasonal and year-to-year variation. River-flow variation directly affects generation because little water is stored for dry periods.
Hydraulic head: The vertical difference in water level that can drive water through a turbine. The available head helps determine how much power a river site can produce.
Pumped-storage hydroelectricity: A grid-storage method that pumps water uphill and later releases it through turbines to generate electricity. It stores energy by cycling water between reservoirs rather than relying on natural river flow.
Capacity factor: The ratio of a power plant’s actual output over time to its maximum possible output. Variable river flow can make actual generation differ substantially from a plant’s rated capacity.
River fragmentation: The interruption of a river’s continuity by barriers that impede water, organisms, or sediment movement. Even low-storage projects can fragment habitat or migration routes at their structures.
Hydraulic turbine: A machine that converts energy in moving water into rotational mechanical energy. The turbine turns the river’s water energy into shaft rotation for a generator.
Dam: A barrier built across a watercourse to hold back or control water. Some run-of-the-river projects use low dams, but they usually create far less storage than reservoir schemes.

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