As the level of the Mississippi falls this year, it allows saltwater to move up the channel:
This will create problems if the river flow gets low enough to allow the salt water to reach the New Orleans drinking water treatment inflow. As the story reminds us, at low water the Mississippi is less than 2 feet above sea level in New Orleans. As the region subsides, and ocean rises, this will decrease. As it approaches sea level, the salt water intrusion will become more severe. While it can be cured by building a sediment damn, that damn will be very problematic for new ships that will be coming through the deepened Panama Canal. As Professor Rogers discusses in this paper, the rising sea level makes it much more difficult to keep the Mississippi dredged to current levels, and may make it impossible to keep it dredged for deeper draft ships:
J. Rogers, The Degrading Mississippi Delta: How Much Longer Can it be Sustained?, 15 Geo-Strata Geo Institute of ASCE 24-29.