The
rate of water consumption in the United States has not increased over the past
five years, according to a U.S. Geological Survey (USGS) report released last
week. Conservation efforts and shifts in technology have helped keep water use
steady, at 408 billion gallons a day, despite the nation's growing population.
However, regional differences in water availability and use will continue to
pose challenges in the future, geologists and policy-makers say.Total water withdrawals from 1950 to 2000 are shown here for each water-use category, showing that the largest users, power generation and irrigation, have remained steady over the past few decades. Note the different scales on the y axis. Image from the USGS report on water use released last week.
Every five years, the USGS Water Resources Division summarizes nationwide water use, breaking the numbers down to track industrial, agricultural, public and other categories of users. In 2000, thermoelectric power generation and agriculture used the largest amount of water, at 48 and 34 percent respectively, followed by public supply at 11 percent of the total water used (both surface and groundwater, fresh and saline). USGS reported that states where population distribution, power production and agricultural needs are greatest had the highest total water use: California, Texas and Florida.
Nationwide, however, the three largest application categories have hovered at steady consumption levels since the 1980s, according to the USGS report. Projections made in the 1960s and 1970s looked for skyrocketing water needs, says Bob Hirsch, associate director for the water program at USGS. He pointed out that even with a 13 percent increase in U.S. population in the 1990s, "water use was virtually unchanged" since 1985.
A number of shifts contributed to this static state, Hirsch said at last week's press conference, including transitions to a more service-oriented, less industry-related national economy. However, the largest effects on water use resulted from legal requirements for power generators and improvements in technology — from widespread installation of low-flow toilets to low-pressure sprinklers for agriculture, according to Sue Hutson, first author of the USGS report.
Hutson notes that amendments made in the early 1970s to the Federal Water Pollution Control Act limited thermal discharges from water-cooled power plants. The plants shifted from sending water only once through the cooling system to a closed-loop process that recirculates water taken from rivers or other sources. "Some of those laws were intended as water quality fixes," Hutson says, but "they affected supply." Increased demand for power has also required power producers to shift from water-cooled systems to combustion plants and air or combined air and water cooling.
Hutson says that the 1992 Energy Policy Act also required low-flow fixtures in all federal buildings, "and of course that moved over to residential buildings." Now low-flow plumbing fixtures are incorporated regularly in all new buildings, including residential and commercial. A decade of such large-scale conservation has made a difference, she says. Hutson expects that the slow replacement of older plumbing systems will further contribute to water savings, but over the next 30 to 50 years, more efficient power plants will replace older ones, considerably reducing water needs.
Nevertheless, water problems will remain in the West, where irrigation and groundwater mining are essential to meet demand. California and other western states are also facing reduced surface water storage with climate changes; earlier melt dates for snowpack mean less water stored for later use, Hirsch says. "People are becoming more and more dependent on groundwater," he says, not only in the arid West but across the country. "That presents a number of scientific and policy challenges."
Where the West once had the majority of irrigated lands (92 percent in the 1960s), the East now has about a quarter of total irrigated acreage, Hirsch says. Salt intrusion into coastal groundwater is also a problem on both coasts, but has been more highly visible lately in the East, particularly in Florida.
And for the first time, Hutson says, water wars are being waged in the Southeast. Historically high rainfall and surface water resources have reinforced the idea, she says, that the Southeast is "the land of plentiful water." But now, with water shortages becoming a potential reality, Alabama, Florida and Georgia are trying to develop water contracts between them. "That's almost unheard of in the Southeast," she says.
David Feldman, a political scientist and environmental policy researcher at the University of Tennessee in Knoxville, says that the new water wars are attributable to "tremendous growth and trends toward urbanization — a change from rural agrarian to urbanized regions," he says, in addition to a growing reliance on public water. Across the nation, fewer people drew water from their own wells, according to the USGS report, relying more on distribution from water companies and utilities.
Also, Feldman says, southeastern states do not yet widely impose the kind of community-level measures more common in the West, such as regulations regarding lawn-watering and other everyday activities. Water rights also differ historically in the two portions of the country, further contributing to the variety of issues and solutions.
Nevertheless, the relatively unchanging rates of water use nationwide show that "conservation and water efficiency are very effective," says Nicholas Cain, spokesperson for the Pacific Institute in Oakland, Calif. The Pacific Institute is lobbying for a national water commission to evaluate and guide U.S. water research and policy. Cain says that considering that the United States has no national water policy, and that states and local organizations set their own courses, "we've done pretty well with a haphazard approach. Now imagine what we could do with an organized plan."
Naomi Lubick
