The Big Dam period in the USA

The Depression in the United States, floods and drastic droughts in the 1930s 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 is 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). Through creating a series of dams, TVA 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.

The US’s demand for energy increased to fuel World War II because the Axis nations had three times more available power than the US. Shipyards, steel mills, aircraft and automobile manufacturers, and chemical companies all required vast amounts of energy. Additional dams made it possible for the US to expand its energy production quickly for war and civilian needs. After the Second World War, hydropower was pumped into peacetime industries, especially farming, with the additional benefit of providing land irrigation.

Early hydro-electric 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 hydro-electric generating stations distributed wherever there was an adequate supply of moving water and a need for electricity. As electricity demand soared in the middle years of the last century, and the efficiency of coal and oil fuelled power plants increased, small hydro plants fell out of favour. Most new hydro-electric development was focused on huge “mega-projects”. The majority of these power plants involved large dams which 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 identified as a cause for concern. 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.