Water withdrawn by U.S. steam-driven power generators fell 18% in 2015 compared to 2010, owing largely to plant closures, coal-to-gas fuel switching, and the use of more water-efficient cooling system technologies, the U.S. Geological Survey (USGS) said in a new report.
The federal entity tasked with providing science and data about natural resources, natural hazards, and land-use said in its June-released report, “Estimated Use of Water in the United States in 2015,” that water withdrawn by the sample of thermoelectric generators in 2015—which produced about 83% (3,230 TWh) of total reported utility power in the U.S.—was 133,000 million gallons per day (Mgal/d) or 149,000 thousand acre-feet/year. Nearly all water withdrawn by U.S. power plants came from surface water: 72% was from freshwater sources. Total withdrawals for thermoelectric power accounted for 41% of total water withdrawals in the U.S., 34% of total freshwater withdrawals, and 48% of fresh surface-water withdrawals for all uses.
|1. Total water withdrawals by state, 2015. Source: U.S. Geological Survey, “Estimated Use of Water in the United States in 2015.”|
As industry professionals frequently point out, the power sector may withdraw large amounts of water compared to other sectors (Figure 1), but it only consumes a fraction of it, mostly from evaporative losses in once-through cooling or closed-loop cooling systems, blowdown, and leakage.
In 2015, the USGS estimated, using data collected from state water agencies, power plant facilities, and federal agencies, including the Environmental Protection Agency, that thermoelectric power plants consumed just 3% (4,310 Mgal/d). “On average, 15 gallons of water was used to produce 1 kWh of electricity in 2015, compared to almost 19 gallons per kilowatt-hour in 2010,” the agency said.
Withdrawal and consumption of water varied geographically. The largest total withdrawals for thermoelectric power were in Texas, where 93% of the withdrawals were from freshwater sources. Texas, Illinois, Michigan, Alabama, and North Carolina each withdrew more than 6,000 Mgal/d of freshwater for electricity generation, which combined accounted for more than 40% of freshwater withdrawals for thermoelectric power. Florida, New York, and Maryland accounted for about 53% of total saline withdrawals for thermoelectric power, nearly all from surface water. Nevada, California, Florida, and Hawaii accounted for 90% of the total saline groundwater withdrawals.
Power plants equipped with once-through cooling accounted for about 96% of total thermoelectric withdrawals (and 37% of net power generated). Plants with closed-loop systems withdrew only 4% of total withdrawals but produced 63% of the sample’s power. Closed-loop system plants, however, accounted for 67% of total consumptive use. “Consumptive use for recirculating cooling systems was 57% of total recirculating withdrawals, whereas consumptive use for once-through systems was just 1% of total once-through withdrawals,” the USGS noted. Another interesting detail the agency reported is that power plants with recirculating cooling systems are found in every state except the District of Columbia and the U.S. Virgin Islands. Power plants with once-through cooling systems are found in every state except Arizona, Colorado, the District of Columbia, Idaho, Nevada, New Mexico, Oklahoma, Oregon, South Dakota, Utah, Vermont, Washington, and Wyoming.
The USGS also reported that the use of reclaimed wastewater was reported in 25 states and totaled 203 Mgal/d, mostly in Arizona (67.7 Mgal/d—and almost exclusively at the Palo Verde nuclear power plant), followed by Texas and Florida.
—Sonal Patel is a POWER associate editor.