NEW ORLEANS — The U.S. Army Corps of Engineers said that it will begin closing the Bonnet Carre Spillway Friday.

In a statement shared on Twitter, the agency said that crews will begin closing 10 bays Friday based on current river conditions. The statement added that the process of closing the spillway will be slow and it may remain open for a month or longer.

Crews have opened 206 of 350 bays on the spillway structure to take pressure off levees further south along the Mississippi River.

The Bonnet Carre Spillway is used to divert water from the Mississippi River to Lake Pontchartrain when the river's water flow gets too high. Plans to open the spillway were announced as the rate of flow at New Orleans approached 1.25 million cubic feet per second, which is what the New Orleans river levees are designed to handle.  

RELATED: Bonnet Carré Spillway opened as Mississippi River swells

The agency opened the historic flood control structure in February, marking the first time it has been operated in consecutive years. It is also the third time in four years that it has been operated.

Brady Skaggs from the Lake Pontchartrain Basin Foundation says in two weeks time about 75 percent of the salty water in the lake has been displaced by fresh water from the river.

While each opening is different, the lake basin normally bounces back pretty quickly after the spillway closes.

RELATED: Lake Pontchartrain filling up with fresh water from Mississippi River

"Since the 2008 opening, each opening has been about a 4 to 6 month period where there's been that rebound," Skaggs said. "It's pretty resilient in that way."

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WWL-TV reporter Paul Murphy and the Associated Press contributed to this report.