ST. LOUIS - A federal judge on Tuesday refused to stop the U.S. Army Corps of Engineers from raising water levels on the Missouri River this week, despite Missouri's concerns that it could add to flooding in the state.

Within hours of the ruling, Missouri Attorney General Jay Nixon filed a notice of appeal with the Eighth U.S. Circuit Court of Appeals in St. Louis. A spokesman said the appeal would ask the federal appeals court to stop the corps from conducting its March spring rise, which could start after midnight.

The corps usually releases extra water in March, and again in May, to prompt spawning of the pallid sturgeon, a fish that managed to survive over millennia but that is now on the endangered species list.

Nixon filed a lawsuit Monday seeking to stop the action, claiming it could add to already heavy flooding the state suffered from torrential downpours last week.

In denying Missouri's request to temporarily stop the water release, U.S. District Judge Jean Hamilton said Tuesday that she saw no evidence to show the corps is not following the law. She said the corps has "ample opportunity" to change its decision to release water if circumstances dictate.

If the corps follows through with its plan, the agency would release extra water into the river from Gavins Point Dam in South Dakota over a two-day period.

John Paul Woodley, the Pentagon's assistant secretary of the Army for civil works, said Tuesday the corps planned to release water at midnight, unless its forecasts changed.

"We would not release water to Missouri or any other state if we felt it would cause a likelihood of flooding," he said, "or pose safety issues for anyone downstream of Gavins Point."

"Our modeling shows water in the tributaries will have dissipated before water (from the release) arrives (in several days).

The corps' Lawrence Cieslik, who oversees water management on the Missouri River basin, and who testified at the hearing, said afterward that corps officials would immediately evaluate data.

Agency guidelines allow the corps to adjust the amount of water or cancel the release altogether if it would exacerbate downstream flooding or upstream drought conditions.

Drought conditions and low reservoir levels upstream caused the corps to withhold March and May releases last year, and the March release in 2006.

Cieslik said the corps continually monitors water levels, weather forecasts and other data to guide its decisions.

Despite widespread flooding in Missouri over the last week, water levels have dropped recently, corps spokesman Paul Johnston in the Omaha, Neb., district office said. The corps had predicted earlier this week that it would be able to increase flows safely.