The Bush administration asked the Supreme Court on Tuesday to let the nation's older power plants draw in billions of gallons of water for cooling without installing technology that would best protect fish and aquatic organisms.

Lawyers for the government and electricity producers urged the justices to overturn a lower court ruling that says the Clean Water Act does not let the government pit the cost of upgrading an estimated 554 power plants against the benefits of protecting fish and aquatic organisms when limiting water use.

They argued that for the last 30 years the Environmental Protection Agency has weighed the costs of controlling power plant withdrawals from rivers, streams and other waterways against the benefits of saving more aquatic wildlife in setting technology requirements.

The law already allows such cost-benefit analyses to be performed when facilities discharge pollutants into waterways that could affect human health, the attorneys said.

"There is no reason Congress would want greater protection for fish from intake structures than for people through the discharge of pollutants," said Deputy Solicitor General Daryl Joseffer.

Environmentalists want the decision upheld, an outcome that could prompt the EPA, under a new administration, to require existing power plants to install more costly and protective technology. All new power plants must use closed-cycle cooling, which recycles water using less from waterways to cool machinery.

Richard Lazarus, an attorney representing environmental groups, said that by comparing costs to benefits the EPA has underregulated water intake from power plants.