Drought Triggers Saltwater Invasion Threatening Drinking Water in New Orleans


The grip of a harsh drought spell in Central United States is causing a significant plummet in the Mississippi River’s water levels. These near-record low levels have enabled a surge of saltwater from the Gulf of Mexico to grapple its way upstream, contaminating the drinking water for thousands of inhabitants residing south of New Orleans.

As the bleak prospect of rainfall in the near future looms, officials find themselves in a race against time to propose effective measures against the saltwater compromising the operation of treatment plants, potentially leaving a considerable portion of the population water-less, including the denizens of New Orleans.

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In a bid to combat the imminent disaster, President Joe Biden granted approval to an emergency declaration requested by Louisiana Governor, John Bel Edwards. The declaration, spanning across four districts namely Plaquemines, St. Bernard, Jefferson, and Orleans envisages that almost a fifth of the state could witness repercussions from the saltwater infiltration into January next year.

When the Mississippi River experiences a dip in its flow rate, its guard against the saltwater from the Gulf of Mexico weakens, allowing it to slither its way inwards. This saltwater spreads from the river’s mouth and advances upstream, forming a dense saltwater wedge due to its greater density compared to freshwater.

The US Army Corps of Engineers has been vigilantly tracking the progression of the wedge toe, which was stationed six miles downstream from Belle Chasse, and 26 miles downstream from the Algiers water treatment plant on September 27th.

Several areas from 15 to 25 miles downstream of the wedge toe have already endured considerable salt intrusion, with the salt content exceeding the standard for public water supply as prescribed by the Environmental Protection Agency. This shortfall in freshwater is owed to an exceptional drought period that has swept across parts of Louisiana and Mississippi.

A significant source of the Mississippi River’s water supply, the states of Minnesota, Wisconsin, Iowa, and Missouri, are also grappling under extreme drought conditions. A lower flow rate in these areas has a ripple effect downstream at the mouth of the Mississippi River. To ward off the saltwater intrusion, the river’s flow rate needs to uphold an above-par pace of 300,000 cubic feet per second. Unfortunately, the current pace at Belle Chasse, Louisiana, is but at half the required rate.

Predictions from the Army Corps anticipate an infiltration of saltwater another 50 miles upstream by the end of October. This intrusion may affect the water supply in four counties, making a potential dent in the lives of more than 800,000 people.

Measures are being undertaken to halt the progression of the saltwater. An underwater levee, initially installed in July, is now being elevated to counteract the saltwater’s advance. Moreover, plans are in motion to deploy a fleet of barges carrying freshwater supplies, serving as temporary relief for the residents. State officials predict the saltwater intrusion could potentially last until January 2024.

As a more sustainable solution, officials are contemplating the construction of a freshwater pipeline. With an estimated cost hovering between $100 million and $250 million, this pipeline would cater to the freshwater needs of New Orleans and the neighboring Jefferson Parish. Officials from the New Orleans Sewerage and Water Board have emphasized that such a pipeline might be the only viable solution, given the enormity of the impending crisis.