How opening the Bonne Carre Spillway could affect the Mississippi River

How opening the Bonne Carre Spillway could affect the river

NEW ORLEANS (WVUE) - The Army Corps of Engineers will open the Bonnet Carre Spillway Wednesday as Mississippi River levels continue to rise.

At a news conference Monday, the Corps said river levels have continued to rise due to excessive rainfall and snow melt in the Mississippi and Ohio River Valleys.

This is the wettest winter in that area in 124 years.

The Corps plans to open 38 bays initially, but could open as many as 200 bays. The Spillway is expected to operate for at least one month.

The Spillway is designed to take water from the Mississippi River and divert it to Lake Pontchartrain. This is the 13th time the Bonnet Carre has been opened -- most recently in 2016 and 2018.

According to Kristi Trail with the Lake Pontchartrain Basin Foundation, this year will be the first the spillway has been opened two years in a row, which could effect the water in new ways.

“So that really is going to be interesting for us to monitor,” Trail said.

The foundation keeps track of what’s going on with the water year-round.

“We sample the lake every single week at 12 different spots all along the perimeter of the lake. We’re also going to be monitoring for the effects of the spillway opening and we publish those on our website at”

The fresh water does have an effect on the brackish lake, but it might take some time. One thing the foundation and fishermen worry about are algae blooms fueled by the warmer weather and nutrients in the river water.

“We did see some algae,” Trail said. “It was an interesting year last year with all the effects. We are not sure if it was related to the spillway or not so it was a good data collection exercise for us.”

Merlin Schaefer, owner of Schaefer Seafood in Metairie said the possibility of algae is concerning.

“How bad the algae bloom will effect and how big it will be, you just don’t know until it happens. That’s the bad thing about the long term openings," Schaefer said.

Some algae can be toxic to animals and as it dies and sinks to the bottom, it will deplete oxygen levels in the water.

“Algae blooms can cause a deficiency in oxygen, which of course our plants and our animals would need to thrive in the lake,” Trail said. "So [what] we want to see is that algae just there temporarily is it something caused by the opening, is it caused by storms, and does it go away.

The good news, according to Trail, is that this seems to be a temporary effect.

“We watch those changes. How it’s happening over the four to six months. but then by the end of summer all that river water is flushed out to the Gulf of Mexico,” Trail said.

For Schaefer, even the threat of temporary change could be bad for business.

“The crabs they not going to stay in the bad water, they’re going to leave. Same thing as the shrimp, fish and everything else,” he said.

In that case, Schaefer said they would just have to follow their lead.

“Then you have to travel where the seafood travels,” Schaefer said.

In the long term, however, Schaefer said the the return of good nutrients in the water made for a good catch last summer and he hopes for similar or better results this year.

As of now, the Corps has no plans to operate the Morganza Spillway near Baton Rouge. It was most recently opened in 2011.

Col. Clancy said one benefit of opening the Bonnet Carre is that no private property will be flooded.

Flood stage for New Orleans is 17 feet and the Corps says opening the Spillway will ensure the Mississippi River doesn’t over-top.

Army Corps New Orleans District Commander Col. Michael Clancy said that once the Spillway is opened, enough water will flow to fill the Mercedes-Benz Superdome in one minute,

The public is allowed to view the spillway opening from the Project Office located at 16302 River Road in Norco. However, drones, and other unmanned aerial systems, are not permitted for flight during the opening.

Army Corps to open Bonnet Carre Spillway

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