Washington ? The government is trying to block a federal judge’s ruling that would greatly reduce the amount of water in the Missouri River this summer.

The Department of Justice planned to ask U.S. District Court Judge Gladys Kessler to stay an injunction she granted conservation groups suing to force a more natural flow along the Missouri to protect endangered birds and fish.

Another court ruling, issued in June by the 8th U.S. Circuit Court of Appeals, said the Army Corps of Engineers must keep enough water in the lower Missouri to allow for barge navigation, power generation and other needs. Several other lawsuits also are pending.

“Because of the apparent conflict, we are likely to file a stay,” Justice Department spokesman Blain Rethmeier said Monday.

Depending on whether a stay is granted, agency officials will decide today whether to reduce the Missouri’s depth by about 6 feet to comply with the order.

American Rivers, Environmental Defense, the Isaac Walton League, the National Wildlife Federation and a half-dozen other groups are suing to force the changes in river flow, which they contend are required by the federal Endangered Species Act.

“This ruling will prevent the corps from wasting valuable water in a drought to float the mere four towboats actually using the river right now,” said Tim Searchinger, an attorney for Environmental Defense. Each boat pulls several barges, each of which can carry dozens of containers.

The lower reaches of the river through Missouri, Kansas, Iowa and Nebraska will be too shallow for barge tows if flows are reduced to levels sought by conservation groups, critics said.

Lower Missouri states also say the more natural flow sought by environmentalists, who also are demanding a spring rise in water levels every third summer to mimic runoff from melting mountain snow, will flood homes and farmland.

In her ruling issued Saturday, Kessler acknowledged barge companies would lose revenues, water quality could suffer and consumers might pay more for power this summer along the Missouri River.

But Kessler said benefits of lower flows outweighed the costs. “There is no dollar value that can be placed on the extinction of an animal species — the loss is to our planet, our children and future generations,” she wrote.

Kessler said conservationists probably would win the lawsuit against the U.S. Army Corps of Engineers because the corps was ordered in 2000 to switch to a more natural flow, with heavier water releases every third spring and lighter flows each summer.

The order came from the U.S. Fish and Wildlife Service, which said that only by implementing the changes could the piping plover, interior least tern and pallid sturgeon, which are on the federal list of endangered or threatened species, be protected.

Changes were due by last year, but the Bush administration postponed them indefinitely by initiating talks between the corps and the wildlife service. The service agreed this year to allow higher flows for this summer only, but the judge called that decision baseless.