Insider Blog: Saltwater intrusion slowing along the Mississippi River

Low water levels along the Mississippi River continue to impact southern Louisiana and greater New Orleans as saltwater threatens local water resources. Limited rainfall and extreme drought have reduced the flow of the Mississippi River to historic lows, allowing saltwater from the Gulf of Mexico to move upstream. This "saltwater intrusion" occurs infrequently at the mouth of the river, but has now affected the area in each of the last two years. The current intrusion developed in the early summer, though the forecast is looking comparatively better heading into fall and winter.

Forecasters were already observing low water levels along the Mississippi River in the early summertime from drought further north in the Upper Midwest. This allowed saltwater to slowly creep upstream into low-lying marshes and smaller communities in southern Louisiana. Water treatment facilities at Boothville, Port Sulphur, and Pointe A La Hache have been inundated for months, costing the state over $30 million dollars so far. An underwater sill, a raised area of the river bed, was installed in July by the Army Corps of Engineers to impede the saltwater's progress. This aided in delaying the intrusion for many of the larger urban areas toward New Orleans, with the forecast continuing to slow in newer updates. The sill was overtopped on September 20th, but then later reinforced; the saltwater intrusion has now been stalled since October 9th due to these efforts.

But not enough rain is on the way to completely stop the saltwater. While precipitation has picked up in the Mississippi Basin in recent weeks, this has only set back inundation for some in southern Louisiana. The saltwater is expected to track upstream toward Belle Chasse by November 30th, though this is weeks later than the earliest forecasts. Many communities closer to New Orleans proper that were previously expected to see inundation will now likely remain at safe levels of salinity. Saltwater will continue to be a problem for the area until efficient rainfall increases the strength of the Mississippi, which won't likely be the case for months.