One of the main uses of water in the power industry is to cool the power-producing equipment. Water used for this purpose does cool the equipment, but at the same time, the hot equipment heats up the cooling water. Overly hot water cannot be released back into the environment -- fish downstream from a power plant releasing the hot water would get very upset. So, the used water must first be cooled. One way to do this is to build very large cooling towers and to spray the water inside the towers. Evaporation occurs and water is cooled. That is why large power-production facilities are often located near rivers, lakes, and the ocean. The evaporated water returns to the water cycle and comes back as rain.
Alternative nuclear reactors can be built to use molten salt in place of water cooling and heat transfer.
Production of electrical power results in one of the largest uses of water in the United States and worldwide. Water for thermoelectric power is used in generating electricity with steam-driven turbine generators. In 2000, about 195,000 million gallons of water each day (Mgal/d) were used to produce electricity (excluding hydroelectric power). Surface water was the source for more than 99 percent of total thermoelectric-power withdrawals. In coastal areas, the use of saline water instead of freshwater expands the overall available water supply. Saline withdrawals from surface water sources accounted for 96 percent of the National total saline withdrawals. Thermoelectric-power withdrawals accounted for 48 percent of total water use, 39 percent of total freshwater withdrawals for all categories, and 52 percent of fresh surface-water withdrawals.