Mississippi River saltwater intrusion threatens Louisiana drinking water - The Washington Post - The Washington Post

Mississippi River saltwater intrusion threatens Louisiana drinking water - The Washington Post

It’s a slow-moving crisis, but one that has sown worry throughout southern Louisiana.

As the “saltwater wedge” continues its march upriver, the mayor of New Orleans signed an emergency declaration. The Biden administration approved the Louisiana governor’s request for federal aid. And the Army Corps of Engineers has raced to safeguard water treatment facilities and slow the saltwater intrusion with extreme measures.

As the situation continues to unfold, here are answers to some of the most immediate questions about what is happening along the river, and what comes next:

How is saltwater from the Gulf of Mexico infiltrating the Mississippi River?

There are multiple factors, but the most urgent one is clear: Drought.

For the second straight year, crippling drought has severely weakened the flow of the Mississippi. In more normal times, the mighty river’s flow is strong enough to prevent salt water from intruding very far upstream.

But the ongoing drought 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, officials say.

That is the primary reason a massive saltwater “wedge” from the Gulf has forced its way about 70 miles inland. In addition, the bottom of the river is lower than sea level nearly until Natchez, Miss. — a topography that makes it easier for salt water to flow upriver.

How does salt water affect drinking water?

On the list of reasons saltwater intrusion is worrisome along the Mississippi, the most immediate and daunting is the threat to drinking water supplies.

Numerous communities in southeastern Louisiana depend on the river as their primary source of fresh water, and intake facilities for municipalities are located along its banks.

As the saltwater wedge creeps further upriver, the likelihood grows that those facilities and the tens of thousands of people they serve could lose access to reliably safe water. Drinking water with high salinity levels poses health risks, particularly in vulnerable populations, such as people with high blood pressure, kidney disease and infants or those who are pregnant.

Plaquemines Parish, where the Mississippi meets the Gulf, has been wrestling with water advisories since June, and officials have been making bottled water available to thousands of residents for months. The parish is working to put in place a number of large reverse osmosis systems at multiple water plants.

“If everything we are doing comes to fruition, we’re going to be fine,” parish president Keith Hinkley said on Wednesday.

If the drought persists and the salt water continues farther up the river, officials say, places with far larger populations could face similar challenges over the coming weeks — including New Orleans.

Louisiana Gov. John Bel Edwards (D) said at a recent news conference that there is no reason for people to panic or race to stock up on bottled water, and he vowed to notify residents who are at risk when the time comes. Meanwhile, leaders of local hospitals, schools and other institutions are making preparations should the problem arrive at their doorsteps.

What are the other threats?

Salt water is not good for pets or crops. It can corrode plumbing fixtures and wreak havoc on industrial machinery.

“It’s been consuming me. … I never thought I’d have to worry about this,” Ricky Becnel, whose farm supplies trees to large retailers around the country, told The Post last week.

Becnel’s nursery, which has been in his family for six generations, sits 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 hotter stretches.

But he and other farmers in the area have begun scrambling to look for alternative water supplies, fearing that they might soon need them.

The equation is even more uncertain for individual homeowners. If salt water were to infiltrate their taps, it can corrode everything from ice makers to hot water heaters. Boiling water does not remove the salt. And reverse osmosis systems, while effective, can be prohibitively expensive.

Is this situation unprecedented?

No. And yes.

In 1988, the Mississippi’s flow dwindled to 120,000 cubic feet per second, the lowest on record. The saltwater wedge that year stretched as far as Kenner, La., on the western outskirts of New Orleans. The Army Corps has said the river needs a flow of more than double that rate to prevent saltwater from moving into the river channel.

Edwards said Friday that this year’s event will probably “be more severe and of longer duration.”

Four times in the past — 1988, 1999, 2012 and 2022 — the U.S. Army Corps of Engineers has constructed an underwater levee, or sill, to try to slow the saltwater from moving along the river bottom. This year, the Corps undertook a similar effort in July.

The Corps is working to expand that underwater levee. The agency plans 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 salt water up the river and buy time for communities not yet affected.

“We’re not going to stop it,” Ricky Boyett, a Corps spokesman, said of the salt water. “But we expect that it will delay it by about 10 to 15 days.”

A dredge is working in the Mississippi River near river mile 64 to augment the underwater sill constructed in July to delay progression of saltwater.— Corps of Engineers New Orleans (@USACENOLA)

For more information on saltwater intrusion visit: https://t.co/hEKjUCVukL pic.twitter.com/UNNWhBLWyp September 27, 2023

What else are officials doing about the problem?

In addition to bolstering the underwater levee south of Belle Chasse, the Army Corps is preparing to barge millions of gallons of fresh water into communities along the southern Mississippi River as the drought continues. The main goal would be to add the massive amounts of fresh water to the saltier water being drawn in at treatment plants, thereby lowering the overall salinity of the water supply.

Locally, officials in Plaquemines Parish are continuing to distribute bottled water to thousands of residents. Numerous schools are stockpiling water for students. Hospitals are gathering water or setting up reverse osmosis systems to ensure clean water for necessities such as dialysis units and labs.

Meanwhile, New Orleans Mayor LaToya Cantrell recently signed an emergency declaration allowing city agencies to prepare for any impending impacts. Earlier this week, Edwards asked President Biden to made a federal emergency declaration, writing in a letter that the crisis could affect almost 20 percent of the state’s population.

On Wednesday, Biden approved an emergency declaration for four parishes: Plaquemines, St. Bernard, Jefferson and Orleans.

Is climate change to blame?

It’s complicated.

“This is just another example of what climate change, drought and sea level rise can look like,” Mark Davis, a professor at Tulane University Law School and director of the university’s Center for Environmental Law, told The Post.

He and others underscore that the current predicament has multiple contributors, including man-made factors such as how the river is managed and dredged, to natural factors such as seasonal variability and the influence of long-term weather patterns such as the current El Niño.

But the warming atmosphere is one unmistakable contributor, he said. While episodes of saltwater intrusion have happened before, the frequency and intensity of recent droughts are new. In consecutive years, severe drought has led to angst and economic consequences all along the river.

“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.

What’s next? And how long will this last?

According to the Army Corps, the tip of the saltwater wedge has made its way roughly 70 miles up the river. The Corps has said that even after its work to enhance the existing underwater sill, the salt water will overtop that barrier.

The agency estimates that the saltwater intrusion will reach Belle Chasse by Oct. 13, St. Bernard by Oct. 19 and Jefferson and Orleans parishes later in October.

Those estimates could change, of course, if significant rainfall were to arrive along the river and give it the water needed to force salt water back toward the Gulf. But that seems unlikely, as forecasts show very little rain in the near future.

More on climate change

Understanding our climate: Global warming is a real phenomenon, and weather disasters are undeniably linked to it. As temperatures rise, heat waves are more often sweeping the globe — and parts of the world are becoming too hot to survive.

What can be done? The Post is tracking a variety of climate solutions, as well as the Biden administration’s actions on environmental issues. It can feel overwhelming facing the impacts of climate change, but there are ways to cope with climate anxiety.

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