At some sites, gauges have reported the phases of the Mississippi River — a measure of water height often used to assess flood conditions — at negative values, an indication of how far the water has receded from normal levels.
There is also a risk of drinking water. The relative flow that reaches the mouth of the river in remote Plaquemines Parish in Louisiana allows salt water to infiltrate the Mississippi River from the Gulf of Mexico, threatening to contaminate the drinking water drawn from the river and requiring emergency action by the Army Corps of Engineers.
Repeatedly over the past week, water levels have become too low for barges to float, requiring the wire to stop sea traffic on the river and dredging channels deep enough even for barges carrying lighter-than-normal loads. Days after a line of stalled river traffic grew to more than 1,700 boats during emergency dredging near Vicksburg, Missouri, a separate 24-hour shutdown began Tuesday near Memphis. More dredging, which routinely costs billions of dollars a year, may be required if boats continue to aground.
The transport industry says the intervention is necessary to maintain the flow of exports which are central to the country’s farming industry. About 60 percent of U.S. corn and soybean exports move down the Mississippi River, Gulf Waterway and the Arkansas, Illinois, Ohio and Tennessee rivers, according to the U.S. Department of Agriculture.
Trade is moving, albeit very slowly,” said Deb Calhoun, senior vice president of the Waterways Council, the transportation industry group. “Ultimately, we need rain, and lots of it.”
Drought appears across much of the country west of the Mississippi, including about two-thirds of the northern Plains states that drain into the Missouri and then the Mississippi, according to US Drought Observatory data.
Precipitation totals rank among the 15 driest states experienced in Oklahoma, Missouri, Kansas, Iowa, and South Dakota for the June-September period. It was the third most dry period on record in Nebraska from summer to fall, according to the National Centers for Environmental Information.
Such a severe constriction of water flows through such a large area has translated into an unusually lasting effect on the levels of the Mississippi River. The last time dry conditions had such an effect on the river was a decade ago.
“If these areas remain dry during the rest of the year, levels could be worse than they were in 2012,” said Jeffrey Graschel, a service coordination hydrologist with the National Weather Service’s Lower Mississippi River Forecast Center. “It remains to be seen how much rain we will get over the next one to three months.”
River levels are not expected to bottom out yet. Graschel said it’s hard to compare current conditions across the record books because the riverbanks have changed dramatically from pre-industrial times — in the Mississippi River alone, the water runs through dozens of locks and dams. But if current drought conditions exceed those observed in 2012, they could approach the severity of the 1988 low-water crisis, he said.
Long-term weather forecasts indicate that there is no significant change in rainfall patterns in the coming weeks. Hydrologists expect persistent drought, as well as newly developing drought areas in the western half of the country this month, according to the Climate Prediction Center.
While the center said it expects near-normal precipitation patterns over the next week or two across the Mississippi Basin, bringing some chances of rain, dry conditions are expected to resume in the later part of October through early November.
Meanwhile, declining river levels are causing costly problems and even Unearthed a shipwreck from the nineteenth century In downtown Baton Rouge.
Plaquemines Parish warned residents on September 28 that drinking water drawn from the Mississippi contains elevated levels of sodium and chloride, a potential health problem for people on dialysis or low-sodium diets. As the southern river’s flow slows, Grashel explained, a layer of salt water from the Gulf of Mexico seeps into the delta, forming a wedge at the river bed because the salt water is heavier than the fresh water.
To protect the community, the Army Corps of Engineers said on September 28 that it would build a sediment barrier across the river channel to prevent more salt water from flowing north.
This work is in addition to the Corps’ routine dredging down the Mississippi which only became more important as the river’s flow dwindled. On average, the wire drags about 265 million cubic yards from the riverbed in the Mississippi Valley each year, spokeswoman Lisa Parker said, at a price of $2.45 billion in 2020.
She said estimates of ongoing emergency dredging work were not available. Parker said the lower water conditions make what was already intense work more difficult, ensuring depths of at least 9 feet along the 4,267 linear miles of canals.
Parker noted that, while costly, working to maintain a viable transportation network on the nation’s inland rivers accounts for what the Wire estimates at $12.5 billion in transportation cost savings, because moving goods over water is cheaper than rail cars or trailers.
For its part, the industry has limited the amount of cargo attached to any one tugboat — just up to 25 boats, instead of 40 models, Calhoun said. However, the boats keep running. US carrier Commercial Barge Line reported that on the Ohio River, the water was low enough that this week barges got stuck near the confluence of that waterway with the Mississippi River.
“This situation underscores the importance of the inland waterways and the Mississippi River as an artery for commerce,” Calhoun said.
But others disagree, saying the problem shows that nature cannot be tamed. Robert Kress, professor emeritus of Earth and planetary sciences at Washington University in St. Louis, said the Mississippi River has changed so much from its normal state, that it has become a “vulnerable system.” Although this fluctuation is often more noticeable during floods, Chris said his research shows that it can affect the river on a daily basis.
“You don’t want things to be unexpected, that’s what we have,” he said. “We have an unpredictable river.”
Until heavy rainfall arrives, river flow is getting some help, for now, as ponds used to store floodwaters along the Ohio and Missouri rivers are emptied to make way for winter storm runoff, Parker said. She added that this is expected to continue only this month – unless the authorities decide to freeze some of the water.
After that, they could be released if river water drops to very low levels in the coming months.