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For a third year in a row, saltwater from the Gulf of Mexico has crept up the Mississippi River, threatening the water supplies of communities in the southernmost portion of the state, WWNO reports.
Previously, saltwater intrusion occurred about once a decade. It occurs where the rate of flow in the river dips below 300,000 cubic feet per second, leaving the river’s freshwater unable to push back against saltwater at its mouth. Last year, saltwater intrusion progressed so far up the river that it affected the drinking water for Plaquemines Parish residents for months, forcing residents to buy bottled water and replace appliances damaged by the salinity.
For the past three years, the U.S. Army Corps of Engineering has funded and maintained a saltwater sill as Louisiana’s main line of defense against the creeping salt wedge. The sill acts as a temporary underwater dam, blocking heavier saltwater molecules from traveling past it while allowing freshwater to flow over it.
But with the intrusions happening more frequently, experts are searching for a longer-lasting solution.
In 2022, the Army Corps spent just over $5 million building the sill. In 2023, that cost surpassed $20 million, mostly due to the Army Corps raising the existing sill a few months after its construction.
