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5 things to know about the saltwater intrusion threatening Louisiana's water supplies

Saltwater is making its way up the Mississippi River in Louisiana and threatening drinking water supplies in the state — and it could soon reach New Orleans. 

Here’s what you should know about the situation. 

It’s being caused by low water levels

The Mississippi River’s flow has declined due to drought that is impacting the river and the water that flows into it from the Ohio River. As a result, saltwater from the Gulf of Mexico is able to push its way toward Louisianans.

Louisiana state climatologist Barry Keim said this happens because saltwater is denser than freshwater, so the salt creeps up because “the flow in the river isn’t strong enough to … hold it at bay.”

“That saltwater basically works its way … up the channel where eventually it starts to reach the intake for some of the water supply,” said Keim, who is also a professor at Louisiana State University. 

While Louisiana itself is facing serious drought, Keim said that the current conditions are likely being caused by what’s happening in the upper parts of the river — which runs all the way up through Minnesota and Wisconsin — and conditions in the Ohio River Valley. 

He added that both climate change and El Niño, a weather pattern that occurs when westward winds along the equator weaken, pushing warm water east toward the western U.S., are likely contributing factors. 

“I would argue what we’re seeing has El Niño’s fingerprints on it; it certainly changes the storm tracks,” Keim said. “Climate change has probably got its fingerprints on it.”

Salt could get into drinking water supplies as a result

Some parts of southern Louisiana are already facing saltwater contamination in their water supplies due to its intrusion in the river, including Plaquemines Parish. Residents there have been under a drinking water advisory, though the parish, Louisiana’s equivalent of a county, has ordered reverse osmosis filters to help treat the water.

Salt getting into drinking water can be a health concern, said Stephen Murphy, who leads Tulane University’s disaster management program. But he said most people will easily be able to tell if they’re drinking elevated levels of it. 

“You and I will certainly taste the saltiness in the water long before it’s a health concern,” Murphy said. “We don’t want people to think that they’re just going to consume a lot of water one day and then wake up the next day with health consequences.”

He said that people who are already on low-sodium diets should start to consider alternatives to tap water, however.

“Depending on your situation, maybe there’s some water that can be delivered by the city. Maybe there’s water that you can start to cobble together,” he said. 

Murphy said that people with high blood pressure and kidney disease, people who are pregnant or have infants, and people who are on dialysis should pay especially close attention to the situation. He particularly warned against feeding infants formula made with salty water. 

Officials are working to mitigate the impacts

State, local and national officials are all working to mitigate the issue.

At the national level, President Biden declared an emergency in Louisiana, authorizing the Federal Emergency Management Agency to mobilize resources and direct federal funding toward water treatment issues in the state. 

Last week, the Army Corps of Engineers said it would bring 36 million gallons of fresh water into the New Orleans area each day via barge. 

The city of New Orleans said it is weighing several options to help it deal with the issue. 

These include blending freshwater from an alternative source in with the saltwater to reduce its salt content, filtering out the salt content or getting water for the city from another source upriver. 

The Louisiana Department of Health is also expected to test the water to monitor for changes. 

Salt-caused corrosion could cause a ‘worst-case-scenario’ with lead exposure

Salt doesn’t just impact people. At extremely high levels, it may also impact pipes. 

If salt is at particularly high concentrations in the water flowing through pipes, it may corrode them. This could both damage the vessels themselves andif they contain heavy metals, cause them to leach those potentially toxic materials into the water.

One such metal is lead, which can cause brain damage in children. 

“I think that’s the worst case and the fear there,” Murphy said. 

He noted that New Orleans does still have some lead pipes and acknowledged that water with high salt levels has the potential to cause corrosion, but he said people still may not end up drinking water that comes through those pipes if it does. 

If it is salty enough to cause heavy metals to leach, Murphy said, people probably will have already switched water sources. 

“A lower concentration for a shorter duration’s probably not going to do much,” he said, referring to salt concentration. “A higher concentration for an extended period of time would probably lead to that, but at that point we might not be consuming that water.”

It may not just be a one-time occurrence

“I do see that this could happen more often in the future,” said Matthew Hiatt, assistant professor in Louisiana State University’s department of oceanography and coastal sciences.

Hiatt said some climate projections indicate future rainfall could be increasingly sporadic, beyond the already naturally low levels in the late summer and early fall. 

And if there are more dry summer months, he said, “we could see consistently low water levels and we might have to deal with saline intrusion.”

The possibility of a future intrusion could mean tough choices for policymakers, as they may want to look to long-term solutions.

“There’s large infrastructure works that are going on right now to try to mitigate the progression of saltwater,” Hiatt said, pointing to an underwater dam being built by the Army Corps.

“Having to construct that and deconstruct that on a regular basis is cost-prohibitive, so it’s probably not a good long-term solution,” he said. 

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