Hydroelectric power includes both massive hydroelectric dams and small run-of-the-river plants. Large-scale hydroelectric dams that continue to be built in many parts of the world contribute to the following damage to the ecosystem:
Hydropower plants can cause low dissolved oxygen levels in the water, a problem that is harmful to riparian (riverbank) habitats and is addressed using various aeration techniques, which oxygenate the water. Maintaining minimum flows of water downstream of a hydropower installation is also critical for the survival of riparian habitats.
Apart from direct contact (fish and other organisms can be injured and killed by turbine blades), there can also be impacts both within the dammed reservoirs and downstream from the facility. Reservoir water is usually more stagnant than normal river water. As a result, the reservoir will have higher than normal amounts of sediments and nutrients, which can cultivate an excess of algae and other aquatic weeds. These weeds can crowd out other river animal and plant-life, and they must be controlled through manual harvesting or by introducing fish that eat these plants.
New hydropower facilities impact the local environment and may compete with other uses for the land. Those alternative uses may be more highly valued than electricity generation. Humans,flora, and fauna may lose their natural habitat. Local cultures and historical sites maybe impinged upon.
For more info about its disadvantages (including advantages), go to Envirothonpa.org and UCSUSA.org.
Discover the different types of hydroelectric power plants and how they each work at RenewableEnergyWorld.com.