The Army Corps declined to disclose to CNN the cost of the current project. T Thomas Berner/APĪnother supply chain crisis: Barge traffic halted on Mississippi River by lowest water levels in a decade Without a permanent fix, temporarily halting saltwater intrusion by creating sills will only cost more in the future, according to Sweet.īarges idle while waiting for passage in the Mississippi River near Vicksburg, Miss., on Tuesday, Oct. The Mississippi River Delta is facing climate and environmental pressures on multiple fronts, including sea level rise, land subsidence, deepening of the channel to allow more vessels and frequent flooding. While the corps expects the sill to successfully prevent saltwater from reaching New Orleans, William Sweet, oceanographer and sea level rise expert with the National Oceanic and Atmospheric Administration, said it’s going to be an increasingly challenging strategy moving forward. Plaquemines Parish officials told CNN that they have secured a reverse-osmosis machine to treat the water and remove salt and other contaminants. “When you’re looking at the areas below the Belle Chase, the smaller water intakes that Plaquemines is using, the parish kind of has the responsibility for mitigating for that saltwater because it is a natural phenomenon,” Boyett said.įor residents relying on drinking water from the Boothville facility, high levels of saltwater-related substances such as sodium and chloride have been detected, and a drinking water advisory is in effect. The unusually low water level is evidenced by the exposed pier cap pile of the bridge. Low water on the Mississippi River in Vicksburg, Mississippi, on October 11. The forecast from the Climate Prediction Center is dry, with below-average rainfall in the outlook through at at least the rest of the week. The river gauge at Memphis dropped to a new low record on Monday – minus-10.75 feet – surpassing the previous low record set in 1988. Dozens of gauges in the river basin are at or below their low-water threshold. “In this case, we’re looking at an area where it’s really not enough rain in the current forecast to change it.”Ī worsening drought in the central US has had a significant impact on the Mississippi River in recent weeks. “The difference is that shortly after we built the sill then, Hurricane Isaac came in and dropped 20 inches of rain in different places, and so it kind of changed the flow rather quickly on us,” Boyett said. He noted that what’s unfolding right now is similar to the low flow seen in 2012. The last time a sill was built at the mouth of the river was in 2012, then 19 before that.īoyett said the problem typically resolves itself once there’s enough rainfall upstream to ease the drought. Salt water in the Gulf of Mexico, which is much denser than the freshwater flowing in the Mississippi, usually pushes up the river every 10 years, Boyett said. ![]() The Army Corps has used this strategy before. The flow rate just north of the planned sill has been running around or below 200,000 cubic feet per second for more than a week, according to data from the US Geological Survey. “When it falls below 300,000 cubic feet per second, it doesn’t have enough force to keep the saltwater at bay,” Boyett said. It will take another week until the sill can be built high enough to block the saltwater intrusion, he said, and it “is designed to be temporary.”īoyett explained that the river’s low flow is the main problem right now. The sill will be roughly 40 to 50 feet high underwater in a location where the water is around 90 feet deep. Ricky Boyett, Army Corps chief of public affairs for the New Orleans District, said the “toe” of the saltwater wedge is already approaching the location of the planned sill. The corps announced last week it would dredge sediment from the bottom of the river and pile it up near Myrtle Grove, Louisiana, to create what’s known as a sill, which will act as a dam for the denser saltwater in the lower levels of the river. The mighty Mississippi is so low, people are walking to a unique rock formation rarely accessible by foot ![]() The Rock itself is separated from the rest of the area by the river and is normally only accessible by boat, but thanks to extremely low water levels it can now be accessed by foot. The geologic formation known as Tower Rock is part of the Tower Rock Natural Area on the Missouri bank of the Mississippi River.
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