The not-so-mighty Mississippi: River's water levels near historic lows for second year in row, leaving New Orleans residents facing drinking water crisis as salty sea water is pushed into watercourse

The Mississippi River's water levels have neared historic lows for a second year in row, leaving nearby residents facing drinking water crisis.  

A salt water wedge slowly creeping upriver from the Gulf of Mexico, due to the unusually low water level in the river, may threaten municipal water supplies, potentially even New Orleans.

The rapid reduction over the last two years is the worst seen since 1988 when a scorching drought overtook much of Middle America. 

President Joe Biden announced Wednesday that federal disaster assistance is available for Louisiana - which is working to stop a mass inflow of salt water. 

The salt is threatening drinking water supplies in the southern part of the state.

Data from the USGS show that at seven gauges on the river, passing through Memphis into Missouri, water levels are 'at or below low water thresholds.' 

The low water level of the Mississippi River is seen as people sit on steps that normally meet the river in the French Quarter of New Orleans, on  September 25, 2023

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2020 versus 2022: The historic river's diminishing water level is blighting those who rely on it for their livelihoods

A man walks along the shore of McKellar Lake, a backwater of the Mississippi River, on October 19, 2022 in Memphis, Tennessee

Data from the USGS show that at seven gauges on the river (signified here with the brown dots) passing through Memphis into Missouri , water levels are 'at or below low water thresholds'

And the issue is not going to go away overnight. 

Experts warned that numbers will continue to drop over the next few weeks - and only a large spate of rain will ease the troubling predictions. 

The mighty river will need at least 10inches of rainfall to keep the salt at bay.  

Katie Dedeaux, a hydrologist for the National Weather Service, told CNN: 'We’re going to need a pretty significant period of wet weather across the basin. It’s not going to be an overnight thing.' 

The saltwater wedge has traveled nearly 15 miles upriver in just seven days, according to the US Army Corps of Engineers, who are building an underwater sill with mud that should slow the flow of saltwater. 

The sill - which will increase the height of the river's bottom by 25 feet - should help halt the movement of the salt. It's being built by Naomi, Louisiana. 

Normally, instances of drought and the need for sills to be built occur every 10 to 12 years on the river. But it is concerning that one is having to be built in 2023 - when the last was only just constructed in 2022. 

Matt Roe, a spokesperson for the Army Corps, said: 'That’s the really notable thing about this year, we did just have sill construction last year, and we’re seeing it again this year.'   

Biden's action authorizes the Department of Homeland Security and the Federal Emergency Management Agency to coordinate all disaster relief efforts, according to the White House.

Additionally, the declaration will allow for more equipment, resources and federal money to address the saltwater intrusion.

In this aerial photo, sediment and mixed river water is seen as a tanker ship moves upriver in Plaquemines Parish, Louisiana, on September 26, 2023

Dredging operations to build an underwater sill are seen, with the city of New Orleans in the background

'I'm grateful to the Biden administration for making this request a priority and responding quickly to help the people of South Louisiana,' Louisiana Gov. John Bel Edwards said.

For the second year in a row, salt water has moved further up the Mississippi, threatening drinking water in communities that rely on the river for fresh water. 

Typically, the river´s mighty flow keeps mass amounts of salt water from reaching too far inland, but hot and dry conditions across the country this summer triggered drought that slowed the Mississippi´s flow and lowered its water levels.

This was also the hottest and the third-driest on record for Louisiana. 

In parts of Plaquemines Parish, the southeast corner of Louisiana encompasses the final stretch of the Mississippi River before it reaches the Gulf of Mexico, residents have relied on bottled water for cooking and drinking since June.

Drinking water advisories have been issued for some communities in the parish, warning people the water is unsafe to drink, especially for people with kidney disease, high blood pressure, those on a low-sodium diet, infants and pregnant women.

Now the salt water is moving further upriver and will likely reach Orleans, St. Bernard and Jefferson parishes by mid-to-late October, officials say.

Pipes carrying sediment crisscross the Mississippi River where the U.S. Army Corps of Engineers is building an underwater sill with mud that should slow the flow of saltwater up the Mississippi River south of New Orleans

A tanker ship moves downriver near dredging operations on the Mississippi River 

A salt water wedge slowly moving upriver from the Gulf of Mexico, due to the unusually low water level in the river, may threaten municipal water supplies, potentially even New Orleans

The river serves as the main artery for US crop exports such as corn, soybeans, and other grains going south to the Gulf. The River is pictured last year

As a result of the drought in 2022, cargo barges and other boats have regularly become moored and stranded, putting waterborne trade and workers' livelihoods in jeopardy

Edwards wrote to Biden earlier this week to ask for federal help. 

In his letter, Edwards said that the issue 'is of such severity and magnitude' that state and local authorities can no longer manage it on their own. 

Federal assistance is 'necessary to save lives and to protect property, public health and safety or to lessen or avert the threat of a disaster,' the governor wrote.

While officials say they are praying for rain to help increase the velocity of the drought-stricken river they are also taking matters into their own hands - raising the height of an underwater levee used to block or slow the salt water and bringing in 15 million gallons of fresh water to treatment facilities in impacted areas.

Lower Mississippi River Forecast Center hydrologist Jeff Graschel told FOX Weather: 'What happens is if we don't get a lot of rainfall in the upper parts of the Midwest, that's really where all the flow comes from.

'By the time the Ohio and the Mississippi Rivers come together, that's about 90% of the water that comes down to part of the lower part of the Mississippi River near New Orleans.'

The river - which flows 2,350 miles from its source at Lake Itasca in Minnesota down through the center of the country to the Gulf of Mexico - was at historically low levels in states such as Illinois, Louisiana, Mississippi, Arkansas, and Missouri last year too.

In 2012 the Great Plains drought - which also saw the Mississippi's water levels reduce drastically - led to $35 billion in losses for the US, and saw officials forced to close off the river at least three times.