Hydroelectricity. Water emerging from a hydroelectric power station. Hydroelectric power is often generated by damming a river and piping the water into turbines coupled to electricity generators. Hydroelectric power causes little pollution but affects local wildlife due to the flooding caused by the creation of the holding lake. A river will also deposit the silt it carries as it enters the lake; the loss of this silt may cause erosion further downstream. A hydroelectric power station may raise its generation rapidly just by allowing more water to flow. As such, these power stations are commonly used during peak demand times. Photograph of Bonneville power station, USA.