WEATHER NEWS: Mississippi River water levels are critically low, bringing some shipping to a halt
The Mississippi River is flowing at its lowest level in at least a decade, and until rain relieves a worsening drought in the region, it’s becoming increasingly difficult to maintain water levels high enough to carry critical exports from the nation’s bread basket.
Areas of persistent and developing drought stretch across much of the Mississippi basin, which itself covers 41 percent of the contiguous United States. Though record-setting storms caused catastrophic flooding in parts of the watershed this summer, the past few months have been among the driest on record in parts of the Heartland, at a time of year when river levels are normally hitting their low points. And long-term forecasts suggest that unusually dry weather is likely to continue.
At some spots, gages reported the Mississippi’s river stages — a measure of water height normally used to evaluate flood conditions — with negative values, an indication of how far below normal levels the waters have receded.
There’s also a risk for drinking water. The relative trickle that is reaching the river’s mouth in Louisiana’s outlying Plaquemines Parish is allowing salt water to intrude up the Mississippi from the Gulf of Mexico, threatening to taint 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 corps to halt maritime traffic on the river and dredge channels deep enough even for barges carrying lighter-than-normal loads. Days after a queue of stalled river traffic grew to more than 1,700 barges during emergency dredging near Vicksburg, Miss., a separate 24-hour dredging closure began Tuesday near Memphis. More dredging, which routinely costs billions of dollars a year, could be needed if barges continue to run aground.
The transportation industry says the intervention is needed to maintain a flow of exports that is central to the country’s agriculture industry. About 60 percent of U.S. corn and soybean exports move down the Mississippi, the Gulf Intracoastal Waterway and the Arkansas, Illinois, Ohio and Tennessee rivers, according to the U.S. Department of Agriculture.
“Commerce is moving, albeit very slowly,” said Deb Calhoun, a senior vice president for the Waterways Council, a transportation industry group. “Ultimately, we need rain, and lots of it.”
Drought is pronounced across much of the country west of the Mississippi, including some two-thirds of the northern Plains states that drain to the Missouri River and then the Mississippi, U.S. Drought Monitor data show.
Precipitation totals rank among the 15th driest that Oklahoma, Missouri, Kansas, Iowa and South Dakota have seen for June through September. It has been Nebraska’s third-driest recorded stretch of summer into fall, according to the National Centers for Environmental Information.
Such a drastic constriction in water flows across such a large area has translated to an unusually lasting impact on Mississippi River levels. The last time dry conditions had such an effect on the river was a decade ago.
If those areas “were to stay dry through the rest of the year, levels could be even worse than we had in 2012,” said Jeffrey Graschel, service coordination hydrologist at the National Weather Service’s Lower Mississippi River Forecast Center. “It just remains to be seen how much rain we get over the next month to three months.”
River levels are not expected to hit record lows just yet. It’s difficult to compare current conditions across the record books because the river’s banks have changed so dramatically from preindustrial times, Graschel said — on the Mississippi alone, waters pass through dozens of locks and dams. But if the current dry conditions surpass those observed in 2012, they might approach the severity of a 1988 low-water crisis, he said.
Long-term weather forecasts suggest no significant change in precipitation patterns in the coming weeks. Hydrologists predict sustained drought, as well as areas of newly developing drought across 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 for rain, dry conditions are predicted to resume for the latter part of October and into early November.
Plaquemines Parish warned residents on Sept. 28 that drinking water drawn from the Mississippi contained elevated levels of sodium and chloride, a potential health issue for people on dialysis or low-sodium diets. As the southward river flow slackens, a layer of saltwater from the Gulf of Mexico is creeping up the Delta, forming a wedge at the bottom of the river because salt water is heavier than fresh water, Graschel explained.
To protect the community, the Army Corps of Engineers said Sept. 28 that it would build a sediment barrier across the river channel to prevent more salt water from flowing northward.
That work is in addition to the corps’ routine dredging of the lower Mississippi that has only become more important as river flow has waned. The corps dredges an average of about 265 million cubic yards of river bottom in the Mississippi Valley each year, at a price tag that totaled $2.45 billion in 2020, spokeswoman Lisa Parker said.
An estimate of ongoing emergency dredging work was not available, she said. But the low water conditions are making work that was already extensive more difficult, ensuring depths of at least 9 feet along 4,267 linear miles of channels, Parker said.
Parker noted that, though costly, the work to maintain a viable transportation network on the country’s inland rivers represents what the corps estimates to be $12.5 billion in transportation cost savings, because moving cargo over water is cheaper than on rail cars or tractor-trailers.
For its part, the industry has limited the amount of cargo attached to any single towboat — only up to 25 barges, instead of the typical 40, Calhoun said. Still, barges continue to run aground. On the Ohio River, even, waters are low enough that barges got stuck this week near that waterway’s confluence with the Mississippi, transportation company American Commercial Barge Line reported.
“This situation underscores the importance of the inland waterways and the Mississippi River as an artery to commerce,” Calhoun said.
But others disagree, saying the problem demonstrates that nature can’t be tamed. The Mississippi has changed so much from its natural state, it has become “a volatile system,” said Robert Criss, a professor emeritus of earth and planetary sciences at Washington University in St. Louis. Though that volatility is often most evident during floods, Criss said his research shows it can affect the river on a day-to-day basis.
“You don’t want things being unpredictable, and that’s what we have,” he said. “We have an unpredictable river.”
Until significant rainfall arrives, river flow is getting some help, for now, as pools used to store floodwaters along the Ohio and Missouri rivers are being emptied to make room for winter storm runoff, Parker said. But that is only expected to continue through this month, she said — unless authorities decide to hold some of the waters back.
Then, they could be released should river waters drop to critically low levels in the coming months.