A saltwater wedge climbing the Mississippi River threatens drinking water

For six generations, Ricky Becnel’s family has run the massive tree nursery on the banks of the Mississippi River near Belle Chasse, La. Its 20 acres and half a million trees, most of them citrus, require pumping about 100,000 gallons a day of fresh water from the river during the warm season.

But in recent days, as saltwater from the Gulf of Mexico has crept steadily up the drought-stricken river and within a mile of Saxon Becnel and Sons, he has scrambled to prepare for very real possibility that the farm’s lifeblood might soon be unusable.

“It’s been consuming me … I never thought I’d have to worry about this,” said Becnel, whose business supplies trees to large retailers around the country.

For the second year in a row, drought has severely weakened the flow of the Mississippi River, allowing a mass of saltwater from the Gulf of Mexico to force its way dozens of miles inland.

The steady creep of that saltwater wedge - which could threaten drinking water supplies in multiple Louisiana communities, undermine agriculture and prove corrosive to infrastructure - has left officials to scramble in an effort to slow down the encroaching sea.

“Based off the current forecast and projections, if no action is taken, we potentially could see the saltwater wedge all the way up to the French Quarter,” Col. Cullen Jones, commander of the New Orleans District office of the U.S. Army Corps of Engineers, said at a recent news conference. “But we have no intention of not taking any action.”

The most immediate action includes expanding an underwater barrier, known as a sill, that the Corps initially constructed in July in an effort to slow the progression of saltwater from the Gulf.

Ricky Boyett, a Corps spokesman, said work on the underwater levee is expected to begin early next week and continue for roughly two weeks. Ultimately, workers plan to create a barrier that rises 60 feet from the river bottom and stretches about 2,200 feet, in an effort to slow the march of saltwater up river and buy time.

“I want to be clear that if the current conditions persist, we will not be able to prevent overtopping of the sill by saltwater,” Jones said. “But we can delay it.”

Keeping that saltwater at bay is crucial.

Already this summer, Plaquemines Parish, where the Mississippi meets the Gulf of Mexico, has been forced to provide bottled water to thousands of residents, as the area struggles with boil water notices and a constant threat of saltwater intrusion.

“It’s been a trial beyond trials,” parish president Keith Hinkley told reporters at the recent news conference.

In a typical year, the flow of the Mississippi is generally sufficient to prevent saltwater from intruding very far upstream. But several factors in recent months have allowed saltwater to find its way at least 64 miles up the river so far.

In particular, the ongoing drought along the Mississippi means that without substantial rain further north, the river’s flow could soon reach as low as 130,000 cubic feet per second - close to its lowest recorded flow ever of 120,000 cubic feet per second in 1988.

That year, the saltwater wedge stretched as far as Kenner, La., on the outskirts of New Orleans.

The bottom of the river, which has been heavily dredged, is lower than sea level until it reaches Natchez, Miss. That topography also makes it easier for salt water to flow along the river bottom, underneath the less dense fresh water.

The underwater barrier that the Corps constructed in July is not unprecedented. It has undertaken similar work in 1988, 1999, 2012 and again in 2022, when a prolonged drought drove water levels on the Mississippi to historic lows.

But as the current drought persists and the river’s flow weakens, Jones said, the Corps determined it had to do more to slow the influx of saltwater. Otherwise, he said, the saltwater wedge is on pace to continue upriver and expected to impact a freshwater intake facility at Belle Chase, La., in early October.

Beyond the perils it poses to drinking water supplies, saltwater intrusion can be corrosive to home appliances and to equipment in industrial facilities. It also can harm crops and complicate caring for livestock.

Even as it works to enlarge the current underwater levee, the Corps said it would leave a “notch” in the sill - 620 feet wide and 55 feet deep - to allow oceangoing vessels to continue to transport cargo up and down the river.

The latest predicament has numerous man-made and natural contributors, said Mark Davis, a professor at Tulane Law School and director of the university’s Center for Environmental Law. But the warming atmosphere is one unavoidable factor.

“This is just another example of what climate change, drought and sea level rise can look like,” Davis said.

He said while the issues posed by saltwater intrusion have happened in the past, the frequency and intensity of recent droughts are new. In consecutive years, he noted, drought has caused angst up and down the Mississippi, from barge operators to farmers to water managers. And those extremes have profound economic consequences.

“It doesn’t mean that every instance is climate, but when it happens repeatedly, the impacts are exactly what climate scientists and experts have been saying can happen,” Davis said.

As fights over water availability rage across the West and elsewhere, Davis said the past two drought-stricken years should serve as a reminder of the need to safeguard the Mississippi’s viability.

“The amount of river it takes to push the Gulf of Mexico back and keep economies going needs to be appreciated, not just along the river, but nationally,” he said. “This river does not have lots of water to share.”

Boyett said the little rain forecast for the Mississippi River valley in coming weeks isn’t nearly enough to change the current calculus. For the river to grow strong enough to once again force the saltwater wedge downstream, it needs to reach about 300,000 cubic feet per second.

“The power of the river is what keeps saltwater out,” he said.

In the meantime, the Corps is preparing for the possibility that it might need to bring water in on barges to help treatment plants reduce salinity and ensure safe drinking supplies. The agency is also working to acquire reverse osmosis systems that can help localities filter out harmful salt.

Becnel also has been watching the forecast closely. With little rain in sight, he knows it could be a matter of days until his once-reliable source of water turns salty. “Time is not on our side,” he said.

He has explored the possibility of digging a well, temporarily drawing from the municipal water supply or investing in his own reverse osmosis system. Every option has downsides. But hundreds of thousands of his trees need water; stores across the country want trees to sell, and generations of his family are counting on the business to press on.

“To say the least, we’re very concerned,” Becnel said. “We’ve got a lot of people counting on us.”