Across the country, extensive and extended drought conditions threaten water supplies. Consecutive years of rain deficits in the Midwest have caused water levels in the Mississippi River to plummet, decreasing the flow rate of the river as it travels south to the Gulf of Mexico. Consequently, the diminished flow at the mouth of the river is insufficient to prevent saltwater from flowing upriver, a situation known as saltwater intrusion. These conditions jeopardize drinking water for approximately 800,000 people from the junction with the gulf north to New Orleans.[1]

At the mouth of the Mississippi, a saltwater wedge is created as the Gulf’s denser seawater meets river water and the saltwater infiltrates under the freshwater. As the river’s water level drops, the wedge creeps farther upstream. A flow rate of greater than 300,000 cubic feet per second is necessary to keep the saltwater from intruding, but the flow rate was only 145,000 cubic feet per second at the end of September.[2] The wedge has moved far enough north that it has impacted several water treatment facilities in Plaquemines Parish.

To mitigate the problem, the U.S. Army Corps of Engineers built an underwater sill to delay the progression of salt water upriver in July 2023; however, saltwater overran the sill on September 2, prompting a 25-foot augmentation. The Army Corps will also distribute millions of gallons of freshwater from upstream via barge each day to treatment facilities that have been overtaken and install reverse osmosis water purification systems to filter the drinking water at Plaquemines Parish (a tool that has been requested by other parishes).[3] Although beneficial, the amount of water being contaminated far exceeds the scope of these solutions. Another option under consideration is to build a multimillion-dollar pipeline that will transport freshwater from upriver. Jefferson Parish has already begun construction on a temporary pipeline for this purpose.

Saltwater is not only unsafe to drink and poses a serious health risk, but also causes damage to infrastructure. In New Orleans, there is added concern regarding possible lead contamination triggered by saltwater corrosion of thousands of lead pipes prevalent to the area. In response to growing concerns, President Joe Biden approved an emergency declaration in September 2023, paving the way for the Federal Emergency Management Agency to assist mitigation efforts.

Although still under construction, the heightened underwater sill has slowed the intrusion’s progression. According to the Army Corps, saltwater will continue to impact both Plaquemines and Saint Bernard Parishes through October with impacts to New Orleans and north predicted for late November.

[1] Zerkel, Eric, and Angela Fritz. “When Will Saltwater Arrive in New Orleans? Here’s What to Know.” CNN, Cable News Network, 29 Sept. 2023, www.cnn.com/2023/09/26/us/saltwater-intrusion-new-orleans-mississippi-climate/index.html.

[2] University of Tulane, School of Public Health and Tropical Medicine, and Sphcomm@tulane.edu. “5 Things to Know about the Saltwater Intrusion of the Mississippi River.” 5 Things to Know about the Saltwater Intrusion of the Mississippi River | Tulane School of Public Health and Tropical Medicine, sph.tulane.edu/5-things-know-about-saltwater-intrusion-mississippi-river#:~:text=When%20the%20river%20falls%20below,145%2C000%20cubic%20feet%20per%20second. Accessed 6 Oct. 2023.

[3] Zerkel, Eric, and Angela Fritz. “When Will Saltwater Arrive in New Orleans? Here’s What to Know.” CNN, Cable News Network, 29 Sept. 2023, www.cnn.com/2023/09/26/us/saltwater-intrusion-new-orleans-mississippi-climate/index.html.