NEW ORLEANS, La. (WWL-TV) – Thursday morning, the Army Corps of Engineers will begin the process of opening up the Bonnet Carre Spillway.

The opening of the bays will happen at 10 a.m. Thursday will be the 12th time the spillway will open since it was completed in 1931.

The move is meant to divert water from the Mississippi River to Lake Pontchartrain. Officials said they look at a few factors when making the decision to open the spillway, including the height of the water in the Mississippi River. How fast the water is moving is also a factor.

When the river is forecast to rise up to 17 feet at the Carrollton Gauge, and the water flow reaches a certain point per second, the corps decides when to open the spillway to keep all of the features such as dams and locks intact.

Authorities said the spillway could be open from 2-4 weeks, which would affect fishing in Lake Pontchartrain.

Nearly 31 states have waterways that drain into the Mississippi River, including two Canadian provinces.