The Depression, floods and drastic droughts in the United States of the1930s inspired a ’big dam’ period that included construction of the Grand Coulee Dam on the Colombia River in Washington, the Central Valley Project in California and the Hoover Dam on the Colorado River. The Grand Coulee Dam remains the largest hydro facility in the US, with capacity of 6,480 MW and plans to increase output to 10,800 MW.
In 1933, Franklin Roosevelt signed the Tennessee Valley Authority Act (TVA), which was designed to create a series of dams. The Act aimed to improve navigation on the Tennessee River, provide flood control, plan reforestation and improve marginal farm lands by creating government nitrate and phosphorus manufacturing facilities at Muscle Shoals.
Early hydroelectric power plants were much more reliable and efficient than the fossil fuel fired plants of the day. This resulted in a proliferation of small to medium sized hydroelectric generating stations wherever there was an adequate supply of moving water and a need for electricity. As electricity demand soared in the middle years of the 20th century, and the efficiency of coal and oil fuelled power plants increased, small hydro plants fell out of favour. Most new hydroelectric development was focused on huge ‘mega-projects’. Most of these power plants involved large dams that flooded vast areas of land to provide water storage and therefore a constant supply of electricity.
In recent years, the environmental impacts of such large hydro projects are being questioned. It is becoming increasingly difficult for developers to build new dams because of opposition from environmentalists and people living on the land to be flooded.