# Run-of-river and small hydro

Hydropower with little or no reservoir, from river plants to village micro-hydro.

Source page: https://www.materialinsights.org/energy/e_small_hydro/

Capture · Water and ocean · No. 30

- Capture
- Output: Electricity or motion
 Capture · Water and ocean · Foundation · Energy

A hydraulic ram lifts water uphill with no fuel or electricity, using the river's own push and just two valves.

Chart: Illustration: Run-of-river and small hydro

##### Where it comes from

Chart: Map of where it comes from

A low weir diverts part of a river into a channel or pipe that runs along a gentler slope, then drops the water to a powerhouse and hands it back.

##### Three things to know

1. Size classes are tidy: small means 1-20 MW, mini 100 kW to 1 MW, micro 5-100 kW and pico anything up to 5 kW.
2. An in-stream turbine in Igiugig, Alaska cut the village's diesel use by a third while running, and cameras saw no injured fish.
3. Many small weirs on one river can fragment it as badly as a single big dam, blocking fish on their way upstream.

##### The journey

1. 1 **River**Water flows with little or no storage
2. 2 **Weir or intake**Diverts part of the flow
3. 3 **Channel or pipe**Runs gently downhill to build head
4. 4 **Turbine or wheel**Pelton, crossflow, Kaplan, wheel or screw
5. 5 **Local use**Mini-grids, mills and village water pumps
 Covered in [Earth's energy flows: sun, wind, water, heat and lifeEnergy](https://www.materialinsights.org/learn/energy/earths-energy-flows/)[Muscles, wood, water and wind: energy before fossil fuelsEnergy](https://www.materialinsights.org/learn/energy/energy-before-fossil-fuels/)

##### Go deeper pick a tab to open it in full

## Other sections

- [Overview](https://www.materialinsights.org/energy/e_small_hydro/overview/index.md)
- [Correlation](https://www.materialinsights.org/energy/e_small_hydro/correlation/index.md)
- [Efficiency](https://www.materialinsights.org/energy/e_small_hydro/efficiency/index.md)
- [Techniques](https://www.materialinsights.org/energy/e_small_hydro/techniques/index.md)
- [Resources and labour](https://www.materialinsights.org/energy/e_small_hydro/resources/index.md)
- [Impact on the biosphere](https://www.materialinsights.org/energy/e_small_hydro/biosphere/index.md)
- [Relationships](https://www.materialinsights.org/energy/e_small_hydro/links/index.md)