These are constructed directly in the river and thus do not need a diversion channel. Since there is no residual water channel, the problem of residual water does not apply. Even though a small build-up is formed, these are not reservoir power plants since the water flows constantly through a turbine.
These take up water from a river via a weir. The water flows to the turbine via the headwater channel, equalising reservoir and pressure pipe, and is then returned to the river. The river section between intake and outlet is referred to as the residual flow.
Here the main purpose of the facility is not energy production, but instead may be drinking water supply, sewage treatment, industrial systems, snow-making systems, etc..