The U.S. Army Corps of Engineers, ordered by a judge to go along with an environmental group’s view of natural cycles, is supposed to manage the waters of the Missouri River so they flow high in springtime and lower in late summer. The Corps just announced it plans to retain more water behind big dams at Gavins Point and upriver, but spokesman Paul Johnston says it’s only for a few weeks.It’s only an April operation, and he says come May they’ll release more water so as tributaries dry up late in summer the Corps can provide minimum navigation flows. A month from now the big dams will let out more water, at an important time for the endangered river birds The terns and plovers begin nesting in early May, so once they’ve built nests the river can’t be raised. But keeping water upriver for the next few weeks is the Corp’s effort to please the many river users with conflicting needs — in this case, fishing and boating industries, upriver along the big reservoirs behind the dams. Releasing less water in April will mean it’s deeper at a critical time for reservoirs, when the game fish are spawning. As for keeping water deep enough for commercial shipping on the Missouri, Johnston says the barge industry’s been having a hard time in recent years. He says a combination of economic forces and the up-and-down flows for navigation the last couple seasons, thanks to drought and lawsuits, have made things so uncertain that shippers have told the corps they won’t even try to sign any contracts to ship to the upper end of the river. That means no barge shipping from ports at Sioux City or Omaha, and the Corps won’t have to guarantee a 9-foot-deep river channel, at least this summer. Judging by spring snowmelt and the snowpack farther upriver in the Rocky Mountains, the Corps agrees with long-range forecasters. Being conservative, they figure drought will continue at least through the end of this year so the engineers will conserve as much water as possible to make enough available for power-plant operators that need it. It’s not likely to be the end of disputes over the conflicting demands for the river’s water, as the supply grows more scarce with continuing drought in the western half of the nation.