This is a very rare event, and it will have repercussions in Lake Pontchartrain for some time to come. Lake Pontchartrain is brackish, a mix of salt and fresh water, and by introducing fresh water in large amounts from the Mississippi River, this will change the salt ratio of the lake. Marine life sensitive to that change will decrease in numbers, so the decision to open the spillway is not something to take lightly. It’s one of those “necessary evils” needed to protect the city of New Orleans and points south. There isn’t much good to be said about a flooding river. For more information about the Bonnet Carre’ and Morganza Spillway openings, please see a previous post on this blog.