Water is one of the oldest energy sources. In ancient Greece, farmers used it to grind grain. Hydropower was believed to be a clean renewable energy source that does not pollute the air or produce toxic by- products.
The earliest hydroelectric dynamo plant was set up in 1870 at Cragside in Rothbury, England. At the Niagara Falls, a hydroelectric facility was built in 1881 to provide lighting for night-time visitors.
The world’s largest hydroelectric station is at the Three Gorges Dam in China. The Itaipu plant on the Parana River, between Brazil and Paraguay, generates the most electricity annually.
Big dam projects can reduce dissolved oxygen levels in water, disrupt river ecosystems, harmwildlife, and displace human and animal populations. The Three Gorges Dam displaced 10.2 lakh people and inundated hundreds of villages.
Hydropower plants can also cause low dissolved oxygen levels in water, which is harmful to river habitats. The presence of hydroelectric dams can often change migration patterns and hurt fish populations.
The promise of carbon-free electricity from hydropower has also been questioned by revelations that decaying organic material in reservoirs releases methane, a greenhouse gas that contributes to global warming.
The ideal hydropower projects are tiny dams or diversions or run-of-river facilities which channel part of a stream through a powerhouse before the water joins the main river.