In 2005, half of U.S. water withdrawals were made by the electricity sector. A “business-as-usual” U.S. electricity future will increase reliance on large thermal power plants and keep water demands high.
Water cooling was first used in thermal power plants in the 1950s. This innovation allowed generator efficiencies and capacities to soar, but also placed a large and growing demand on the U.S. water system. This will continue in Maintain and Migrate, which both rely on thermal power plants.
While most of the water withdrawn by the electricity sector is used for cooling and subsequently returned to the source, there may still be serious consequences. Aquatic life requires particular combinations of flow rate, temperature, acidity, and mineral content, all of which can suffer damaging changes. When used, water is released back into streams and rivers, it must not only be cleaned, but also cooled to tolerable temperatures to reduce its harm to fish populations or limit excessive algal growth; this in turn requires still more water.
Kenny, J. F, N. L Barber, S. S Hutson, K. S Linsey, J. K Lovelace, and M. A Maupin. 2009. Estimated Use of Water in the United States 2005. Reston, Virginia: U.S. Geological Survey. link