Washington ? A federal judge held the Army Corps of Engineers in contempt Tuesday for refusing to lower Missouri River water levels to protect endangered birds and fish.

U.S. District Judge Gladys Kessler ordered the corps and the secretary of the Army to comply by Friday or pay half a million dollars for each day her order is disobeyed. She said she might consider “more draconian contempt remedies” if flow is not cut by July 31.

Kessler ordered water levels dropped in a July 12 injunction she granted conservation groups that are suing to alter the Missouri’s flow.

The corps has refused to comply, saying her order conflicts with an earlier Nebraska federal court ruling requiring enough water for barge shipping and power generation.

The groups want the Missouri to ebb and flow as it did before it was dammed and channeled decades ago to provide constant depths for barge shipping and other uses. The goal is to encourage spawning and nesting to help sturgeon and shorebird species on the government’s threatened and endangered lists.

“The Missouri River’s heartbeat, long flatlined by the corps, is about to get a brief and partial shock back to life,” Chad Smith, spokesman for lead plaintiff American Rivers, said Tuesday.

Kessler’s order was to cut the flow, beginning last week, on the lower Missouri River through Nebraska, Iowa, Kansas and Missouri.

She conceded Tuesday that “a conflict may exist” with the Nebraska federal court ruling, but she said a conflict did not excuse the agency from obeying her order. And she accused the government of dragging its feet in responding to the injunction.

Justice Department lawyers representing the corps sought emergency stays last week that were rejected by Kessler and the U.S. Circuit Court of Appeals for the District of Columbia.

“Moving to stay an order does not represent a good faith effort to comply with that order,” Kessler wrote. “Rather, it represents an effort to postpone compliance with that order in the hope that it will be overturned on appeal.”

More serious penalties could include higher fines or even jail time.

There was no immediate response Tuesday evening from the corps. Justice Department lawyers defended the agency in court, and Justice spokesman Blain Rethmeier said, “We’re reviewing the judge’s decision and will evaluate our options now.”

The next option for the government would be to request a Supreme Court emergency stay from Chief Justice William H. Rehnquist, who handles emergency matters from that appeals court.

The reductions in Kessler’s order would halt navigation on the Missouri, dropping depths at Kansas City, Mo., from about 14 feet to 8 feet — too shallow for barges carrying grain and other cargo to the Mississippi River at St. Louis.

Barge and farming interests say the corps has an obligation to provide enough water for barge shipments.

The sport fishing industry and other upstream interests would benefit from low summer flows that would keep more water in upstream reservoirs in Montana and the Dakotas.

Debate has dragged on for more than a decade over the seasonal changes and whether they should become part of the corps’ Master Water Control Manual for operating the Missouri River.