Most forms of electric power production require the use of water. Water is withdrawn and heated into steam that drives turbines to produce electricity. The water is also used to cool and condense the steam back into water and to cool equipment at the station. The amount of water used at each power station varies depending upon the size of the station, the type of cooling water system in place, and the fuel source.
In 2011 and 2012, Dominion voluntarily participated in the Carbon Disclosure Project’s (CDP’s) Water Disclosure Questionnaire. Dominion's responses to the CDP Water Disclosure Questionnaire contain detailed information on water withdrawals, water risks, and water management at Dominion. Copies of the 2011 and 2012 Dominion CDP Water Disclosure can be found at https://www.cdproject.net/. The chart below compares the 2010, 2011 and 2012 annual surface water withdrawals for electric power stations across Dominion’s operations. Data for stations that have been shut down or sold has not been included in the Annual Surface Water Withdrawals graph.
Surface Water Withdrawal vs. Surface Water Consumption
As mentioned above, most electric power stations withdraw water to cool equipment and to create steam that turns turbines to produce electricity. In most cases, stations that withdraw larger amounts of water return nearly all the water withdrawn to the original source. The water returned from these power stations, known as once through cooling stations, is not consumed and keeps the water available for downstream users.
Other types of stations, known as closed cycle cooling stations, withdraw less water, but nearly all of the water withdrawn evaporates and is not returned directly to the original water body. The graph above depicts the mix of Dominion power stations that employ once through cooling versus and closed cycle cooling.
Freshwater vs. Saltwater Use
Approximately 57% of the water used by Dominion comes from salt or brackish water bodies. Withdrawals for drinking water and agricultural water nearly always come from freshwater sources. Thus, Dominion power stations that withdraw from salt or brackish water bodies do not typically compete with drinking or agricultural water supplies.
Some Dominion electric power stations withdraw from man-made lakes or reservoirs. Dominion operates three power stations on made-made lakes (North Anna, Mount Storm, and Kincaid). These freshwater lakes were created by electric utilities at the same time the power station was built and the lakes are specifically constructed to support power station operations.
Dominion also operates power stations on freshwater rivers and lakes, such as the Great Lakes. Nearly all (more than 90%) of the fresh surface water withdrawn by Dominion from these rivers and lakes is returned to the original water body and relatively little water is consumed by these stations.