The thermoelectric power category includes water used in the generation of electric power with fossil-fuel, nuclear, or geothermal energy. The estimates of water withdrawals for thermoelectric power should be reliable because relatively complete files on power generation are maintained by Federal and State agencies. The Electric Power Annual is prepared by the U.S. Department of Energy, Energy Information Administration, and contains information about electric power net generation. Most of the water withdrawn by thermoelectric plants is used for condenser and reactor cooling. Plants vary widely as to the techniques used in the disposal of the cooling water after it is passed through the condensers. Less water is required when cooling water is recycled through cooling towers or ponds, but a higher percentage of the cooling water is evaporated (consumptive use), usually more than 60 percent. When the water withdrawn for cooling is used only once before it is returned to a surface water body, significantly more water is required, but evaporation is low (less than 3 percent). Water-withdrawal estimates generally were made based on power generation. Consumptive use estimates were based on coefficients ranging from 1 to 100 percent of withdrawals.
The quantity of water used for thermoelectric power generation during 1990 was 131,000 Mgal/d of freshwater (the same quantity as in 1985), and an additional 64,500 Mgal/d of saline water (tables 23: water-resources regions and table 24: State) (15 percent more than in 1985). Thermoelectric power water use by source is shown by hydrologic region in table 25, and by State in table 26. Thermoelectric power accounts for 39 percent of total freshwater use for all offstream categories and represents 48 percent of combined fresh and saline withdrawals. Fossil-fuel thermoelectric plants accounted for about 73 percent of total thermoelectric withdrawals; nuclear plants, 27 percent; and geothermal plants, less than 1 percent. Saline ground water was only reported for geothermal plants in California (41 Mgal/d), Nevada (32 Mgal/d), North Dakota (0.3 Mgal/d), and Utah (7.9 Mgal/d), and is not listed in the tables or included in the totals. Thermoelectric fresh and saline withdrawals were about 1.4 times the water withdrawn for irrigation, the next largest category.
The source and disposition of water for thermoelectric power are shown in the pie charts below (or as a GIF file or as a PostScript file (92Kb)). Surface water was the source for more than 99 percent of total thermoelectric withdrawals, and about 33 percent of the surface-water withdrawal was saline. Thermoelectric power plants furnish most of their own water; less than 0.1 percent is obtained from public supplies. About 2 percent of the water withdrawn for thermoelectric power (fossil fuel, nuclear) during 1990 was consumptively used as a result of once-through, cooling-tower, or pond cooling.
About five times more water was used in 1990 for thermoelectric power generation in the eastern part of the United States than in the western part to generate about twice as much power. The Mid Atlantic and South Atlantic-Gulf water-resources regions, where surface water is plentiful, led the nation in both fresh and saline withdrawals (figure 26 (GIF file), or as a PostScript file (508Kb)). By State, New York, Illinois, California, Florida, Texas, Ohio, and New Jersey accounted for about 43 percent of total thermoelectric withdrawals (figure 27 (GIF file), or as a PostScript file (508Kb)). Illinois and Ohio led the nation in freshwater withdrawals for themoelectric power generation (figure 28, or as a (PostScript file (508Kb)).