Drought across the Mississippi watershed has lowered water levels in the river enough to allow salt water intrusion from the Gulf of Mexico, threatening drinking water supplies, aquifers, and infrastructure.
Federal emergency declares as the Corp of Engineers ships in water on barges.
This will be happening more often in the future.
Saltwater intrusion in southeast Louisiana is officially a federal emergency.
Why it matters: President Biden signed a declaration Wednesday unlocking additional federal support as local officials look to thwart the threat of salt entering the drinking water supply in metro New Orleans.
Catch up quick: Because of the drought across the Mississippi River Valley, salt water is creeping upriver, where many communities, including New Orleans, draw their drinking water.
- The salt water on Wednesday was just south of Belle Chasse, according to Col. Cullen Jones of Army Corps of Engineers.
- The latest forecast calls for it to reach New Orleans around Oct. 22. The water in Orleans and Jefferson parishes is safe to drink until then.
- Once the salt is here, it is expected to stick around for weeks to months, depending on rainfall.
Threat level: People and animals can’t drink water with high salt levels.
- Salt water also is corrosive and can damage pipes.
The big picture: The current mitigation efforts – barging in fresh water and using reverse osmosis desalination systems – will not be enough to keep salt out of drinking water in Orleans and Jefferson parishes, leaders said Wednesday.
- They said they’re looking for permanent solutions with regional benefits.
- Those solutions will come at a cost, with a federal ask between $100 million and $250 million or more. But securing funding shouldn’t be a problem, says Collin Arnold, the director of the New Orleans Office of Homeland Security and Emergency Preparedness.
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.
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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.
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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.
–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 and, if 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.”
–“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.