Washington ? America’s water use has been stable since the mid-1980s despite population growth, a sign that conservation works, researchers from the U.S. Geological Survey said Thursday.

Water use in the United States totaled 408 billion gallons per day in 2000, the same as in 1990 and down from 440 billion gallons per day in 1980, the agency reported.

“The message is that humans are adaptable creatures,” said Robert M. Hirsch, the Survey’s chief hydrologist. “To me that is a very positive message.”

Water use climbed steadily along with population from 1950 to the peak in 1980, Hirsch said, but declined to 399 billion gallons per day in 1985. It remained relatively stable since then, despite a population increase of more than 40 million people.

Usage of 408 billion gallons per day represents 1,430 gallons per person, Hirsch said, though most of that is for industry and agriculture. Household use, he said, is about 100 gallons a day per person.

The biggest use is for cooling water for power plants and agriculture, but each has instituted conservation measures in recent years, Hirsch reported.

Power plants, for example, reuse cooling water several times and some are turning to air cooling, while irrigation methods have become much more efficient in recent years.

Daily use of water for electrical generation declined from 210 billion gallons in 1980 to 195 billion gallons in 2000, the report said. And for the same period irrigation use declined from 150 billion gallons per day to 137 billion gallons per day.

Moving in the other direction, due to population growth, was the use of water from public water systems, where daily use increased from 34 billion gallons in 1980 to 43 billion gallons in 2000. There also has been an increase in the share of population connected to public water systems, Hirsch noted.