The ongoing drought in Louisiana has caused the Mississippi River to drop to one of its lowest levels in recent history, allowing saltwater from the Gulf of Mexico to intrude into the freshwater supply. This poses a serious risk for millions of residents, especially in the New Orleans area, who depend on the river for drinking water.
Saltwater intrusion worsens despite mitigation efforts
Saltwater intrusion is a process where saltwater from the sea or ocean moves into freshwater sources, such as rivers, lakes, or aquifers, reducing the quality and quantity of freshwater available. This can happen when the freshwater flow is reduced due to drought, overuse, or climate change, and the saltwater wedge advances upstream.
The Mississippi River is the main source of drinking water for many communities in Louisiana, including New Orleans, which draws water from the river at two locations. The river also supports navigation, agriculture, industry, and wildlife in the region.
However, the river has been experiencing low water levels and flow rates due to the prolonged drought that has affected much of the state. According to the U.S. Drought Monitor, most of the central and southern regions of Louisiana are currently under extreme or exceptional drought conditions, the highest levels of severity.
This has allowed saltwater from the Gulf of Mexico to creep up the river, reaching as far as 90 miles upstream from the mouth of the river. Saltwater intrusion can affect the taste, odor, and safety of drinking water, as well as damage pipes, equipment, and crops.
To prevent the saltwater from reaching the water intakes, the U.S. Army Corps of Engineers built an underwater sill, or an artificial levee, in July to create a basin that would hold back the saltwater. However, last week, the water level in the Gulf rose above the sill, allowing the saltwater to flow over it.
The Corps is now working to raise the sill by another 25 feet, which is expected to take about 24 days to complete. This would delay the saltwater intrusion by another 10 to 15 days, but not stop it completely.
Drinking water advisories and emergency declarations issued
The saltwater intrusion has already impacted some areas in Louisiana, especially in Plaquemines Parish, where the saltwater reached the Boothville Water Treatment Plant. A drinking water advisory is in place from Empire Bridge to Venice on the west bank and Phoenix to Bohemia on the east bank of the river, due to high salt levels in the water. Residents are advised to use bottled water for drinking, cooking, and brushing teeth.
The parish has set up bottled water distribution locations at local fire stations and is working to bring in fresh water via barges. The parish president, Kirk Lepine, said the situation is “critical” and urged residents to conserve water.
Other communities along the river, including St. Bernard, Orleans, and Jefferson parishes, are also at risk of being affected by the saltwater intrusion in the coming weeks. New Orleans Mayor LaToya Cantrell signed an emergency declaration for the city on Friday, authorizing the Sewerage and Water Board to take necessary measures to protect the water supply.
Louisiana Gov. John Bel Edwards said he is considering requesting a federal emergency declaration from President Joe Biden to help address the crisis. He said he is in contact with the Corps, the Federal Emergency Management Agency, and other agencies to coordinate the response.
He also urged residents not to panic and to stay informed from credible sources. He said the state has been through a similar situation before, in 1988, and has learned from it.
“We are monitoring this situation very closely and applying the lessons learned,” he said. “It is extremely important for the public to stay informed and only rely on credible sources for updates during this event.”
Rainfall needed to restore freshwater flow
The best solution to the saltwater intrusion problem, however, is beyond the control of the officials. It is rainfall.
Rainfall would increase the water level and flow rate of the Mississippi River, pushing back the saltwater wedge and replenishing the freshwater supply. However, the forecast for the region does not show much hope for significant rainfall in the near future.
According to the National Weather Service, the river is expected to fall to historic lows in the next few weeks, reaching 1.5 feet above sea level at the New Orleans gauge by mid-October. The normal level for this time of the year is about 6 feet.
The low water level also affects the navigation and commerce on the river, as ships have to reduce their loads and draft to avoid grounding. The river is a vital artery for the transportation of goods and materials, such as grain, coal, oil, and chemicals, across the country and the world.
The drought and saltwater intrusion are just some of the challenges that Louisiana has faced this year, along with wildfires, heat waves, hurricanes, and the COVID-19 pandemic. The state has been declared a major disaster area four times this year, more than any other state.
The governor said the state is resilient and will overcome this crisis, but also called for action to address the root causes of climate change, which is exacerbating the frequency and intensity of extreme weather events.
“We have to do everything we can to mitigate the effects of climate change and to adapt to the new normal that we’re living in,” he said. “We have to be good stewards of the environment and the resources that we have.”