Chamberlain, S.D. ? High water destroyed Charlotte Cadwell’s marina on Lake Francis Case in 1997, so she rebuilt. Now the 72-year-old woman faces a different foe: low water.

Receding levels have wiped out the Missouri River reservoir’s precious walleye fish eggs, made it difficult for fishermen to launch their boats and left Cadwell unable to rent some docks. Her restaurant and bait shop are suffering, too.

“We live in hope. We hope every day the water is going to be up,” she said.

That puts her right in the middle of a decadelong legal and political battle over how the U.S. Army Corps of Engineers uses its dams and reservoirs to manage the water level of the drought-stricken Missouri River, which flows 2,341 miles through seven states.

Cadwell and many others in the upstream states of South Dakota, North Dakota and Montana want the corps to keep water levels high for the benefit of fishing and pleasure boating.

But people downstream worry that any big changes could hurt barge traffic, farmers, power companies and other businesses in Iowa, Nebraska, Kansas and Missouri.

The fight is expected to intensify any day now when the Corps of Engineers issues its recommendations for revising the Master Manual, which governs the way the river is managed. The revisions have been 12 years in the making.

The Missouri River drains one-sixth of the United States, with a basin that includes all or parts of 10 states. It begins at Three Forks, Mont., and empties into the Mississippi River at St. Louis. It has six reservoirs four in South Dakota and one each in Montana and North Dakota.

The Corps of Engineers tries to juggle the competing interests along the river. Everyone agrees the No. 1 priority is flood control to save lives and property, said Paul Johnston, a corps spokesman in Omaha, Neb.

But after that, priorities differ according to where people live.

At stake on one side are the tens of millions of dollars in revenue from fishing and other recreation, and, on the other side, the untold millions from industrial and commercial operations.

In deciding how the Master Manual should be revised, the corps has six options. The two main ones: keeping the current operating plan, which maintains a fairly even flow from spring through fall, or adopting a seasonal ebb and flow.

The U.S. Fish and Wildlife Service and environmentalists are backing the ebb-and-flow plan, which would boost spring releases and cut summer flows to mimic conditions that existed before the river was dammed and channeled between the 1940s and the mid-1960s.

Environmentalists see ebb-and-flow as a way to protect endangered fish and birds such as the pallid sturgeon, the least tern and the piping plover. Some upstream interests favor that option, because it would involve releasing a lot of water only once every three years.