JACKSON — A $1.6 million study will look for ways to restore lost wildlife and plant habitat along the lower Mississippi River while maintaining flood defenses and navigation.

The Nature Conservancy is giving $400,000 toward the U.S. Army Corps of Engineers’ study. Leaders of the environmental group hope to unseal many of the backwaters and side channels stopped up in efforts to confine the river to a single channel. Historically, those areas were key for wildlife populations.

The study, scheduled to be completed in 2014, will examine areas from Cairo, Ill., where the Ohio River joins the Mississippi, to the river’s mouth in south Louisiana.

Wells Fargo & Co. is donating $200,000 to The Nature Conservancy for the study. A ceremony was to be today in the bank’s Jackson office.

“This is important to us because we’re the nation’s largest agricultural lender and because the Mississippi provides drinking water to 18 million people,” said Jay Lawrence, spokesman for the nation’s fourth-largest bank, based in San Francisco.

Gary Young, who helps plan projects of the Corps’ Vicksburg District, said the Corps has never done a study like this on the lower Mississippi. He said it could produce a list of project proposals for which the Corps and local communities could seek money.

Though the river is undammed below Cairo, levees have cut it off from its traditional flood plain. Rock dikes seal off many oxbow lakes and side channels, while underwater dikes channel the current in the river.

“It’s generally recognized to have been pretty heavily impacted,” said Michael Reuter, director of The Nature Conservancy’s Great Rivers Partnership.

Many environmentalists have long regarded the Corps of Engineers as an enemy. For example, environmentalists opposed efforts to build giant pumps that would drain Mississippi’s Yazoo basin, north of Vicksburg. But Reuter said that a similar study in the northern reaches of the Mississippi River has led to habitat restoration being factored in to Corps’ planning in those areas.

Steve Haase, also of the Great Rivers Partnership, said the lower Mississippi study could build on previous efforts. For example, a group of state environmental and wildlife agencies identified 239 projects that would improve habitat and recreation between Cairo and the Gulf of Mexico. Many of those involve reconnecting backwaters and side channels that have been sealed off, or cutting notches in dikes. Among other benefits, more sluggish backwaters can give fish a place to lay eggs outside the powerful current of the main channel.

The previous state-level effort has already resulted in some projects being completed, including restoring flow to a side channel near Clarksdale and habitat restoration work on an island just north of the Interstate 40 bridge in Memphis.

Haase also points to the recent removal of sections of a levee along the Ouachita River in Louisiana. That project allows the Mississippi tributary to seasonally flood 17 square miles of land that is part of a national wildlife refuge. Flooded bottomlands help reduce the height of water downstream, as well as provide spawning grounds for fish and habitat for ducks and geese. Sluggish floodwaters can drop sediment and fertilizer over land instead of shooting them out into the Gulf of Mexico, where they create a giant “dead zone.”

The trick is to achieve environmental improvements without increasing risks of flood damage or decreasing its ability to act as a highway for barge traffic.

“A lot of the habitats that were there before these alterations have simply gone away,” Haase said. “How much can the river be altered to allow flow back into them without causing the problem that led (dikes and levees) to be put there in the first place?”

The study was in the planning stages before last spring’s floods. But Haase said that event, which surpassed the epic 1927 flood in some places, including Vicksburg, reminded people that it’s important to consider the whole river when making changes in one area.

“It really got people to think again about how this thing acts as a system,” he said.