Bonnet Carre Spillway Opened to Control Rising Mississippi River

In what has been touted as the wettest winter in the region in over a century, the Mississippi River continues to rise and poses a risk of flooding to New Orleans and other river towns along the Mississippi. To avoid that scenario, the Army Corps of Engineers has opened the Bonnet Carre Spillway to divert some of the river water and relieve pressure on the New Orleans levees and drainage system.

This news has drawn much attention because this is the first time that the Spillway will be opened for two years in a row – after 2016 and 2018.

The Spillway is meant to drain water from the Mississippi River and the Ohio River Valley to Lake Pontchartrain. This will be the 13th time that the Spillway has been opened and it is expected to operate for at least a month. 

Too much water

The river water has been rising because of excessive rainfall as well as melting snow and ice. Initially, the Army Corps of Engineers plans to open only 38 bays, but if needed, as many as 200 of the 350 bays could be opened. 

What will be most interesting to note is how the river water affects the water of the lake, considering this is the second time in a year that the Bonnet Carre is being opened. It is noteworthy because the lake is brackish while the river is fresh water.

According to the Lake Pontchartrain Basin Foundation, an organization that monitors the lake and watches closely for any changes in it, the warm water and nutrients from the river can lead to growth of algae in the lake, which is concerning.

Since a large number of organisms live in the lake, from fish to crabs, the growth of algae could rob them of the oxygen they need for survival.

Some forms of algae are toxic and can be harmful to the plants and animals that live at the bottom of the lake. This will either kill them or make them go away to a different water body.

Changing water may affect water creatures

The good news is that the foundation believes any change caused by algae will be temporary. Come summer, most of the water from the lake will be washed to the Gulf of Mexico. However, even temporary changes can make the underwater creatures look for better living conditions, and that’s going to hurt the seafood industry.

On the other hand, the river water bringing back nutrients in the lake could facilitate the growth of many new organisms, something that happened in the past every time the Spillway was opened.

There is also the Morganza Spillway near Baton Rouge, which was last opened in 2011, but the Corps said it doesn’t plan to open that. Commander Col. Michael Clancy of the Corps said that the biggest benefit of opening the Bonnet Carre Spillway is that no private property will be flooded. 

The public is even allowed to watch the opening of the Spillway, and it is an event that consistently draws many spectators.