Hydropower is one of the oldest and most used environmental friendly ways of producing energy. It has been used for more than 2000 years. Unfortunately most of the rivers which are suitable for a hydropowerplant are already exploited so it is getting more and more difficult to find places to big new plants and extend the hydropowermarket.
Even though hydropower is considered environmental friendly, it does affect the environment in and around a river in several ways. Different impacts like flooding, sedimentation, erosion, stratification, preventing fish from travelling etc.