Hydroelectric power has long been a staple of the world’s renewable energy. In fact, 80% of the world’s renewable energy comes from hydroelectric power.  Hydroelectric power comes in different forms ranging from large scale damming projects to the small “run-of-the-river” plants.  Now, the demand for clean energy is becoming increasingly higher and higher as global climate change from greenhouse gases gets worse and worse. But how clean is hydroelectric power and what is the true impact it has on the environment?
Large scale damming projects are the main supplier of hydroelectric power. An average large scale hydroelectric power plant can produce electricity anywhere from 250-10,000 Megawatts depending on the size. However, the largest hydroelectric power plant in the world, the Three Gorges Dam, is capable of producing 22,300 Megawatts. Besides building these massive dams, another hindrance to hydroelectric power is the need for a reservoir. Reservoirs are needed to control the flow through dams and to ensure that the ecosystems on the river remain balanced. But it is with these reservoirs that the most problems with hydroelectric power occur. First, the reservoir area must be flooded which destroys wildlife habitats and plant life. The decomposition of plant life as a result of the flooding is actually the worst environmental impact hydroelectric power has. As the plants decompose they release carbon dioxide and methane. Second, water levels downstream must be kept constant or the river will dry out and harm animal and plant life. Third, reservoir water is stagnant so there is more of a buildup of sediment and other nutrients which results in an excess of algae and other aquatic weeds. This excess of algae crowds out other plant and animal life, so a system of algae removal is necessary. Lastly, water evaporates much faster than it would in the river because the water is stagnant. Still, these hydroelectric power plants have way better carbon emissions than natural gas and coal. The United States does not plan on making anymore large scale power plants but it will continue to improve existing ones.
Small “run-of-the-river” projects have minimal impact on the environment mainly because large reservoirs are not needed. Typical hydroelectric power systems of small size produce around 10 Megawatts. This is a small amount of electricity but it is enough to supply all the electricity needed for a small community. Small hydroelectric systems are ideal systems for off-the-grid living and are relatively inexpensive. A person can make their own hydroelectric system for as little as $1000.