Mississippi River Salt Intrusion: In the New Orleans region, rumours of a water shortage have caused a run on bottled water over the past few days. Governor John Bel Edwards addressed this issue Friday along with a larger discussion on saltwater intrusion of the Mississippi River.
Understanding Mississippi River Salt Intrusion
To further understand the most recent data available, we contacted Stephen Murphy, PhD, Director of the Disaster Management MPH Programme in the Department of Environmental Health Sciences at Tulane School of Public Health and Tropical Medicine.
Due to the absence of rainfall in the Midwest during the past two months, more saltwater from the Gulf is flowing upriver and replacing freshwater flowing downstream.
Due to the absence of rainfall, the river’s flow is just too weak and shallow to stop the heavier saltwater from migrating inland and upriver.
When a sill strikes it, it acts as a type of “ramp,” “kicking up” the wedge off the bottom so that the river’s current has a better chance of pushing it back downstream.
In order to handle ever-larger oceangoing boats, the Mississippi River was deepened to 45 feet in 1986 and to 50 feet in 2022. As a result, the riverbed in the NOLA region is now substantially lower, and the whole Mississippi River is below sea level throughout the state.
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When the river’s flow rate drops below 300,000 cubic feet per second, it is unable to stop salt from the Gulf of Mexico from rising. We could see Mississippi River flows as low as 130,000 cubic feet per second in our vicinity. The flow rate as of September 22 is 148,000 cubic feet per second. It might take months for the Mississippi and Ohio River valleys to receive 10 inches of precipitation, but that amount is probably necessary for the river to reach a high flow rate that can push the saltwater wedge back downriver.
The area has previously been affected by saltwater. Due to the fact that the sill was constructed in 1988 too late to prevent saltwater from migrating as far north as Kenner, the Corps later adopted the regulations that resulted in the current sill’s construction beginning in July.
What issues could we be dealing with?
About 15 to 25 miles downstream of the front/toe of the saltwater wedge, surface waters will reach a secondary level of 250 ppm chloride, exceeding the U.S. Environmental Protection Agency public water supply threshold. According to WHO drinking recommendations, at about 200 ppm, individuals won’t want to drink it because of the flavour. Those on salt-free diets shouldn’t go over 20 ppm.
Note that once the level hits 250 ppm, water systems issue a health advice. Long before the amount of salt in the water reaches unhealthy levels, people will not appreciate the flavour of it.
Systems used to distribute water do not filter it. In lower parish communities, burst pipes have already occurred as a result of exacerbated drought conditions in the soil/ground causing shifts combined with the weakening onset caused by the corrosive saltwater. When saltwater is pumped through a water distribution system, it can cause pipes to corrode, potentially leaching heavy metals from the pipes and pipe fittings into drinking water, and can also lead to pipe failure.
Concerns about agriculture also exist because of the huge areas that the lower MS River irrigates as well as the livestock farms.
What steps are taken to address the problem?
The sill, an underwater barrier, will be made larger. It will be raised to 30 feet below surface level and extended outward above its current 1,500-foot length. It is now estimated to be 45 feet high in an area 90 feet deep.
With unique one-way traffic regulations, a 625 foot-long notch in the sill will be kept over the river’s navigation channel to a depth of 55 feet below the water’s surface. This will allow ocean-going vessels to continue moving up and down river. Ocean-going ships using the river are permitted to have a draught of 50 feet, which is 50 feet deeper than the new elevated part of the sill without the notch.
The local water supply will be combined with water that has been barged in to lower the salt content to acceptable levels.
Additionally, point-of-use testing will be increased by officials to maintain better situational awareness, and smaller facilities in Plaquemines Parish will treat their water using reverse osmosis technology.
In order to lessen the effects of a potential greater salt level in the water for infant formula, the state is obtaining pre-made formula for WIC programmes.
Is the water still safe to drink?
Yes. Water is safe to drink right now, but according to the EPA limits mentioned above, the taste of the water may soon be too salty for some people to tolerate.
If any effects occur, they won’t be felt for a few weeks, according to experts. But in the absence of precipitation, we should prepare for a disruption to our systems in late October or early November.
Mississippi River Salt Intrusion Effects
The more serious effect—which could need to be addressed by reducing usage—may be the corrosive effect on pipes and appliances. The duration of this catastrophe could be much greater than it was in 1988. It will be crucial to pay attention to local authorities on health.
Right now, it wouldn’t be a good idea to run for the water. Once more, the water is safe right now. Having said that, it’s crucial to always be aware of your water usage. It’s a good idea to keep some on hand for storm-related difficulties, and it might also be a good idea to gradually increase that amount. Even if our region requires additional water, there will still be water accessible. Officials have emphasised that this potential water demand is local and not widespread outside of our region. Only buy what you actually need if you must buy water.
