Since this past summer, saltwater has been slowly moving up the Mississippi River from the ocean in a natural process known as saltwater intrusion, appearing in drinking water of local residents. With a major city, New Orleans, just miles upstream, officials are racing to avert a large-scale water crisis, though progress has been slow. In this article, we take a look at how this crisis arose and what can be done to contain it as well as avoid similar events from happening in the future.

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Saltwater has been invading the Mississippi River from the Gulf of Mexico over recent months, posing a major threat to public health in the New Orleans area. This summer, residents in the river delta basin region south of New Orleans began to notice saltwater in their tap water and pipes. The issue persisted for months, making national headlines and prompting state and federal declarations of emergency.

The Mississippi River – the second-longest river in the United States – runs across nearly the entire north-to-south length of the country, passing through ten states before flowing into the Gulf of Mexico through Southeast Louisiana. The river’s massive size is typically sustained by substantial yearly rainfall across the middle of the country, as well as waters from its tributary rivers like the Ohio and Missouri rivers. When at its normal levels, the river water can pass undeterred all the way to the Gulf of Mexico. Yet raging droughts over the last year have seen water levels fall drastically (in fact they fell so much that a 1915 shipwreck of a trade vessel was discovered in shallow waters last year). 

Without the river sustaining its high mass and velocity, saltwater from the Gulf of Mexico has been able to start pushing upstream in a process known as saltwater intrusion.

What Is Saltwater Intrusion?

Far underground, water permeates the ground beneath an invisible line called the water table. At levels this deep, the water saturation is dense enough that water can easily be drawn from the ground via springs or wells. These regions of the underground are called aquifers, and they make up the vast majority of the global freshwater supply.

More on the topic: Depleted Aquifers: Causes, Effects, and Solutions

Saltwater intrusion occurs when saltwater from the ocean slowly moves into and occupies space in freshwater systems like rivers and aquifers. While the ground layers beneath the land are usually full of fresh water, the ground beneath the oceans is salty. When these underground freshwater and saltwater layers meet, they push against each other, and this is where saltwater intrusion can occur. 

Since saltwater is far denser than freshwater, it usually exerts greater pressure and naturally encroaches inland. This process can be further accelerated when the freshwater levels in the ground deplete, often a consequence of aquifer over-pumping or river dredging, as well as climate-caused factors like droughts and sea level rise.

Rivers pose a unique risk as they allow a way for saltwater to reach areas further inland, which is what is happening in the Mississippi River. 

Because of an extreme lack of rainfall in the midwestern and southern US, the Mississippi River’s volume has dropped significantly. In fact, the river reached record low levels just last year. In addition, sea levels around Louisiana have been steadily rising at a rate of one inch (2.54 cm) every two years since 1950. These two factors craft the perfect setting for saltwater intrusion, as the river no longer has its usual mass to force the saltwater back as it empties into the Gulf of Mexico.

Saltwater is then slowly able to force its way upstream along the very bottom of the river in what is known as a saltwater “wedge.” As it travels up the river, it acquires ready access to infiltrate inland aquifers and seep into community water systems.

What Are the Dangers of Saltwater Intrusion?

When consumed, saltwater can have serious adverse effects on the body. The system is put at major risk, and resulting complications (like hypertension) can lead to more critical issues like heart attacks and strokes. Other bodily systems are at risk too, such as the kidneys, digestive system, and even skin defects, which can arise from washing clothes or showering with salt-contaminated water. 

Saltwater intrusion also has a negative impact on local biodiversity and the environment. As saltwater penetrates rivers and aquifers, it introduces salinity levels far too high for many plant and animal species to survive in. Vegetation is crippled and many animal habitats are disturbed, leading to the displacement and disruption of balanced food chains.

It is not just the local area of the intrusion that is affected. Saltwater can significantly contribute to greenhouse gas emissions through its accelerated decomposition of peat, a natural material that sequesters carbon in high concentrations. As peat decomposes, carbon is released into the atmosphere. This contributes to rising temperatures and climate events like droughts and sea level increases, which are the prime conditions for more saltwater intrusion to occur.

The situation in Louisiana has also exposed another major issue plaguing New Orleans and much of the rest of the US: lead pipe infrastructure. 

Lead pipes were frequently used in the first of the 20th century to build up public and private water systems, though they are now of course widely known to pose a major risk to public health. Saltwater is much more corrosive than freshwater and, when it gets into water systems, it can easily corrode lead pipes, which leeches toxic substances into drinking water. New Orleans, like many other cities, does not even know exactly where all of its lead pipe infrastructure is located across the city.

In 2021, the Biden administration pushed congress to pass the Bipartisan Infrastructure Law, and a major portion of that law aims to replace all lead pipes in the country within the next decade. Billions of dollars are packed into the law in hopes to revitalize and modernize the country’ infrastructure. However, it is a race against the clock, as saltwater waits for no one and the public’s health is at stake.

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How Are Officials Addressing the Situation?

The US Army Corps has carried millions of gallons of fresh water to affected communities via barge, blending it with the river to reduce the salt content and freshen the water in treatment plants. Plans have also been put in place by a few municipal areas to construct pipelines to import freshwater from sources further inland. 

New Orleans had a $200 million pipeline planned for construction, but these plans have been tabled for now as the saltwater’s progress has significantly slowed in recent weeks. Efforts like these provide immediate relief to affected areas but they are quite expensive and only temporary solutions, and can contribute to the problem in the long run by over-pumping water in other areas.

A major construction technique employed by the US Army Corps of Engineers is to prevent (or at least slow down) saltwater intrusion by constructing water sills on the river floor. These are ground barriers (think underwater levees), designed to impede the saltwater wedge progressing upstream along the bottom of the river. 

Before this year, sills had been built four other times in the Mississippi River, in 1988, 1999, 2012, and 2022. However, this year the saltwater progression has been so strong that it overtopped last year’s sill construction. Alterations have since been made to strengthen them against the progression of the salt, a move that has, so far, been successful in keeping the saltwater from reaching New Orleans. 

Also helping slow the progression are large natural holes along the bottom of the river, for the extremely dense saltwater must fill these holes before progressing further upstream.

Is it Possible to Remove the Salt From Saltwater?

Desalination is another possible, yet controversial, solution to saltwater crises. There are a variety of methods that remove salt from water, the most common form being solar desalination, where saltwater evaporates and then later falls back to the earth as rain. 

Apart from this natural process, humans have developed a few mechanistic techniques to generate freshwater from saltwater. The first large-scale evaporator was built in Kuwait in 1951, and since then, the technology has advanced, resulting in the increased construction of desalination plants all over the world, especially over the last two decades. 

Desalination is most commonly used in the Arabian Peninsula, nearly 6 billion gallons of saltwater are pumped from the ocean each day to meet a majority of the countries’ freshwater demand. The US is in the process of constructing more and more desalination plants, though often to significant public backlash. 

Desalination plants are expensive and energy intensive, consuming vast amounts of electricity and emitting carbon dioxide into the atmosphere at rates at the level of tens of thousands of cars. These plants also disturb local habitats and biodiversity, not just because their construction disrupts local species, but also because of their waste discharge. 

The recovery ratio for desalinated water is inefficient, with only one liter of water produced for every 1.5 liters of its waste, a briny discharge. This discharge is not only extremely high in salt content, but it also contains chemicals like chlorine, copper, and other potentially toxic agents used in the desalination process.

There are a few different procedures to conduct desalination; some common forms are electrodialysis, evaporation, and reverse osmosis. Reverse osmosis filters are currently being deployed in water treatment plants in the affected Louisiana communities, and it appears desalination will continue to grow as a popular global freshwater solution. It is critical for governments and corporations to put more effort into regulating the technology so that it is deployed in the most clean, equitable, and efficient way possible.

What Is the Outlook on the Situation?

Officials no longer expect New Orleans to be significantly impacted by the saltwater intrusion, however, a few more nearby parishes downstream do expect saltwater to penetrate their water supply by late November. While it looks like drastic consequences will be avoided in the large metropolitan area of New Orleans, thousands of people have been and will continue to be impacted.

Questions have been raised regarding the amount of dredging that the Army Corps of Engineers has conducted in the Mississippi River over the last century. Over-pumping and dredging are known to create unstable conditions that lead to aquifer depletion and contamination, but economic priorities have seen public health risks ignored in the service of other goals. These ongoing events act as a forewarning to other coastal regions on the dangers of saltwater intrusion, which is far reaching throughout the country, but are also a reflection of the overall groundwater crisis impacting much of the world today. Responsible management of the nation’s water systems is critical moving forward, if crises like that in the Mississippi River are to be mitigated in the future.

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The post The Saltwater Crisis in the Mississippi River, Explained appeared first on Earth.Org.

As the world grapples with escalating water scarcity, one of the most pressing challenges is the depletion of aquifers, underground reservoirs that provide a significant portion of our freshwater supply. Across the globe, countries are witnessing a steady decline in aquifer levels, posing severe threats to ecosystems, agriculture, and human livelihoods. In this article, we delve into the causes and far-reaching effects of low aquifer levels, while examining the innovative solutions that some nations have embraced to combat this alarming crisis.

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Last month The New York Times released the results of their investigation into the groundwater crisis in the United States, and their findings are extremely concerning. 

Using data from over 80,000 wells, the investigation revealed aquifer levels are critically depleting nationwide. Around 45% of wells have shown significant decline since 1980, and 40% have reached a record low in the past decade, with 2022 being the most damaging so far. With 90% of the United States’ water systems supplied by aquifers, agriculture and sustainable access to food and water is already facing serious jeopardy.

The US is not the only country in a crisis. Europe is facing a “steady depletion” in aquifer levels across nearly the whole continent. Regions of Bangladesh, a country that usually struggles with too much water during monsoons, have been forced to completely shift their agricultural practices to deal with depleted and contaminated groundwater. Decades of urbanisation have monumentally reduced aquifer levels in cities like Nairobi, Kenya, and Kabul, Afghanistan. Droughts and a rising population have seen Australia’s groundwater problems reach the brink of crisis. 

Reliable access to groundwater has become dire, and with climate change accelerating out of control, reliance on aquifers only grows more precarious.

What Is an Aquifer?

Underground, in layers of permeable rock and sediment, sits 97% of the world’s liquid freshwater. You can find water in all layers of the ground, but closer to the surface it is in lower supply. At enough depth, below a line called the water table, the ground becomes so saturated with water that this can easily and quickly be drawn out via springs or wells. This saturated area beneath the water table, where most water is drawn from, is called an aquifer. 

The Water Table. Image: USGS.

Water from aquifers is used by everyone, from individuals to corporations to governments, and used for many vital purposes, such as supplying a home with drinking water or irrigating an industrial crop farm. 

Typically, rainwater or other forms of water runoff replenish the aquifers over time so they stay full, saturated, and stable. However, over the last half-century, water has been pumped out at an unsustainable rate. Water regeneration lags well below the rate we pull water from the ground, and since aquifers typically replenish the water levels of rivers and lakes as well, aquifers are emptying out and all global freshwater has been put at risk.

The Aquifer Recharge Cycle. Image: Govt. of Newfoundland and Labrador.

Why Are Aquifer Levels Falling So Low? 

After World War 2, technological advancements in pump technology rapidly developed. The US agriculture industry quickly utilised this technology to accelerate the scale of agricultural production. This turned the US into an international behemoth in agricultural exports, and from the 1950s onward farms around the world followed suit. 

For instance, from 1950 to 1985, India doubled the land area irrigated by surface water but increased by 113 times the land area irrigated by aquifers. A 2012 study showed that China’s groundwater use for irrigation rose from 10 billion cubic meters a year in the 1950s to over 100 billion cubic meters a year in the 2000s. Overall, agriculture accounts for around 70% of global freshwater withdrawal.

While the main culprits for aquifer depletion are the agriculture industry and drinking water systems (aquifers supply 2.5 billion people with their sole source of drinking water), it is important to keep in mind that many other practices contribute heavily to this issue. Oil, gas, coal, and many mining industries both drain and pollute groundwater resources at very high rates and in general industrial factories use water at an unsustainable level.

With so much water being used, one would think that regulation is in order, but that is not the case. Governments across the world struggle mightily to implement proper regulation. 

Companies like Nestle have been able to lobby their way to access public groundwater for decades. Some US states have rules that allow aquifers to be drained completely. Farming monocultures have increasingly dominated the agricultural industry, with a 2020 study showing that 70% of the world’s farmland is operated by 1% of its farms. A few countries, such as Chile, even allow private companies to obtain “perpetual ownership” of water assets.

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What Are the Effects?

Water scarcity, already a major issue, will only proliferate as groundwater reserves run dry, but food scarcity will also grow, too. With agriculture acting as one of the main causes of groundwater exhaustion, it also will become one of its main victims. In the face of climate change and water depletion, farming methods will need to continue to find ecologically conscious solutions to these issues if agricultural systems are to become sustainable.

Aquifers are also at major risk of pollution. Excessive pumping can cause all sorts of contaminants to reach underground water systems, and it is very difficult to remove these pollutants. Dangerous acids, metals, and other chemicals can easily infiltrate groundwater as side-effects of mining, drilling, and other invasive practices. Groundwater pumping in coastal areas can also result in saltwater intrusion, allowing saltwater to contaminate freshwater and essentially render it unusable.

Another cause for concern is land subsidence. When water is extracted from the ground, much of the ground’s mass is removed, causing the land to irreversibly sink lower and lower.  A 2022 Stanford Study has shown that California land may continue to sink for centuries unless aquifer levels are regenerated, and this issue is similarly occurring throughout the world, in China, Indonesia, Mexico, and many other countries.

Sources of Groundwater Contamination. Image: GRID-Arendal.

What Solutions Are Being Implemented?

With no end in sight to the global water crisis, water conservation is key to managing a sustainable source of water in the decades to come. Solutions can come in a variety of forms, from political regulation to technological advancement, but dedication and creativity are key to mitigating this impending global catastrophe. 

Managed Aquifer Refresh is a critical technique that has been successfully implemented to refresh aquifers across the world, such as in Bangladesh and China, by using various techniques to collect freshwater, treat it, and put it back into the ground. Some of the methods are quite innovative as well.

Many cities and towns in the US state of Virginia are using treated sewage wastewater to recharge their aquifers in a practice that is not as gross as it sounds. Beijing transfers water from nearly 1500km away in order to maintain a flexible and steady flow and supply of water that can fluctuate based on demand. Communities in central Kenya have been able to utilise sand dams to create self-perpetuating water and agricultural systems. 

Governments, corporations, and even individuals must all be willing to adjust their practices and follow strict regulations if there is to be hope of balancing global groundwater levels. There is still time, and as governments and industries become more aware of the fact that they need to adapt, policy changes have already been implemented to conserve what little water is left and replenish it to its former levels. Not all is lost, and innovative methods are helping mitigate catastrophe for now. But more must be done, and soon.

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