One of the most important and large source of renewable energy, Hydropower contributes to 10% of world electricity generation. The flowing water energy is converted to electricity in the hydropower plants. Most commonly the dam water is used. Flowing water through turbines ii used for the power generation. Although there is no air emission however water quality and wildlife habitats can be affected. Work is going on to design the power plants in such a way that it causes minimum affect to the river water. Undoubtedly it improves the wildlife’s river habitat but at the same time cause the reduction in power plant output. Sometimes this power plant hinders the life of the fishes so different approaches are employed such as fish ladders and improved turbines to assist the migration of fishes and lower their death rate.