Every dam causes some impact on the environment.
Whether its purpose is hydroelectricity production, flood control or irrigation, a dam is, after all, a barrier across a river a very concrete obstacle to the river s natural course and functions. For many years now, campaigners, local affected communities and scientists have catalogued the many ways in which dams interfere with the ecosystem. The more immediate effects are obvious the loss of lands, farms, forests and valleys to the dam s reservoir. Three hundred square kilometres of land are to be flooded behind the Ilisu dam. A dam also regulates the flow of the river , controlling the release of water according to electricity production or irrigation needs.