The U.S. Army Corps of Engineers yesterday did an about-face and abandoned a plan to change the way it manages the Missouri River, even though it has publicly acknowledged that the current system violates the Endangered Species Act. The U.S. Fish and Wildlife Service has said for years that the river must be returned to a more natural flow in the spring to prevent the extinction of the river’s pallid sturgeon, piping plovers, and least terns. The Corps agreed last December. But U.S. President Bush sided with the barge industry and farm interests during the presidential campaign last year, and promised to block a spring rise in the river. The move by the Corps not to endorse a rise enraged USFWS officials and Senate Majority Leader Tom Daschle (D-S.D.); environmentalists suggested they would sue if natural flows weren’t restored.