The Pacific Institute, an Oakland-based think tank that focuses on water issues, released a report Wednesday that shows total water use in the United States declined over a period that ended before the current California drought began.
The report shows total water use in the five-year period ending in 2010 is lower than in 1970, despite continued population and economic growth.
The report analyzed data from the U.S. Geological Survey.
"Remarkably, water use in 2010 was down in all sectors - agriculture, municipal and industrial, and thermoelectric power," said Heather Cooley, the Institute’s Water Program Director and report co-author. "Reductions in water use for thermoelectric power generation – the single largest use of water in the U.S. – accounted for nearly two-thirds of the reduction in water use between 2005 and 2010. This represents an important reversal of a 25-year trend of increasing water use to produce energy."
"We've seen energy efficiency improvements which reduce the total demand for energy and thus, the water required for cooling that," said Cooley. "We're seeing more renewables, and in particular wind and solar photovoltaics, which use a very small amount of water."
Cooley also said that water use for agricultural irrigation was at its lowest level in more than 40 years during the period, even while the number of acres irrigated increased. The report said shifting to less water-intensive crops and improvements in irrigation technologies and practices were among the reasons for the reduced use of water by the agriculture sector.
"For example, since 1985, the acreage irrigated by surface flooding, the least efficient irrigation method, has declined, while the acreage irrigated by sprinkler and micro-irrigation methods has increased," said Cooley. "We're seeing greater adoption of more efficient irrigation systems, including drip systems. We're also seeing changes in the water intensity of the crops that are grown."
The report shows that, from 2005 to 2010, water use in the United States declined 17 percent to 1,200 gallons per person per day, levels not seen since the 1940s [and the single largest decline in any five-year period.]
Even with the improvements in water management, Cooley warned that the current rate of use is not sustainable.
"Despite the reductions we've seen, national water use remains high and many fresh water systems are under stress from overuse," said Cooley. "We also know that population growth and climate change is going to affect the supply and demand for water."