Insider Blog: Saltwater creeping up the Mississippi River

Drought has been the big story in recent months and impacts continue across the nation into the fall. Extreme to exceptional drought has expanded along the Gulf Coast in a few short months, and combined with the ongoing dryness further north, the Mississippi River is feeling the strain. River levels have dropped so low in southern Louisiana that salt water from the Gulf of Mexico is slowly creeping back upstream, and could soon threaten the city of New Orleans.

This process is known as saltwater intrusion and is a somewhat common occurrence in the low elevations along the Gulf Coast. When the force of the ocean is great enough to overcome the freshwater flowing downstream, unusable saltwater can infiltrate water treatment facilities and remain a nuisance for months. Currently, as of late September, the saltwater has crept upstream just over 6 miles south of Belle Chase and is expected to impact New Orleans by mid-October.

As saltwater is denser than freshwater it travels along the river bottom and can be impeded by obstacles that slow the progression upstream. But the only way to fully reverse this process will be beneficial (and unlikely) rainfall across the Mississippi River Basin. It would take nearly a foot of precipitation across this widespread region to restore freshwater flow to necessary levels, and this isn't probable in the short-term forecast. As a result, the city of New Orleans is bracing for impacts lasting into early 2024, with plans to barge in millions of gallons of water a day.