LA - Here’s Why Salt Water Is Invading the Mississippi and Whether It Will Happen More Often
Raging floods, intensifying drought and rising seas could affect saltwater intrusion
CLIMATEWIRE | The drought-driven wedge of salt water creeping up the Mississippi River is deepening a mystery about one of the world's mightiest waterways.
How will climate change affect the river?
There are relatively few scientific studies on how warming is reshaping the Mississippi, and even fewer on saltwater intrusion from the Gulf of Mexico. The void comes as climate change threatens to alter the second-longest river in North America through raging floods, rising seas and prolonged drought, having extraordinary effects on the people who live in more than 100 cities and towns nestled along its banks.
Scientists admit that gaps in their understanding about the effects of rising temperatures on the river have left them searching for answers about the saltwater wedge that is slowly moving upriver toward New Orleans, where it could jeopardize freshwater supplies by next month.
But they say there are a number of ways climate change could be affecting the wedge.
Droughts are expected to grow more frequent and intense across much of the U.S., meaning dry spells like the one affecting the river now could happen more often. That has helped the wedge move upriver from the Gulf because the depleted river flow isn't strong enough to stop it.
But heavy rainfall events are also intensifying, potentially increasing the risk of floods — and preventing salt water from creeping into the channel. It’s still unclear which factor is likely to have the greater influence.
Sea levels are also rapidly rising along the Gulf Coast. That could increase the risk of saltwater intrusion on the river, scientists say — but they aren’t sure by how much.
And there are plenty of other human factors to consider. The Mississippi is one of the most heavily engineered rivers in the country, with dams, levees, reservoirs and frequent dredging. These practices can affect the river’s flow, making it difficult to parse out the influence of climate change compared with other forces. This is the second year in a row that salt water has entered the river, and the fourth time since 1999.
“It’s still very much an open question what’s going to happen in the future of the Mississippi and the degree to which the trends we’ve been seeing over the last few years is the result of climate change,” said Samuel Muñoz, a hydrology expert at Northeastern University.
