Low water shouldn't disrupt Mississippi barge traffic

The Mississippi River at Cape Girardeau is forecast to fall to its lowest point in nearly three years later this month, but the river should remain navigable, according to the U.S. Army Corps of Engineers.

The river gauge at the Cape Girardeau riverfront stood at about 17.5 feet Thursday afternoon, dropping from a crest of nearly 21.4 feet a week earlier. By Dec. 17, the National Weather Service predicts it will fall to 10.3 feet.

“Navigation is always our first priority,” said Sue Casseau, public affairs officer with the Corps of Engineers’ district office in St. Louis, which is responsible for maintaining a 300-mile navigation channel along the Mississippi between Hannibal, Missouri, and Cairo, Illinois, that is at least 300 feet wide and a minimum of 9 feet deep.

“Nine feet is the channel requirement,” she said, “but what I cannot say for sure is if the (Cape Girardeau) gauge reflects the actual depth of the channel.”

The gauge, Casseau explained, measures the river stage from a point on the river bank, but does not necessarily indicate the depth of the navigation channel that is likely several feet deeper.

“For instance, when we had low water eight or nine years ago, the St. Louis gauge was measuring below zero, but barges were still going,” she said. “So the gauge may not be a reflection of the depth of the channel.”

The river bottom “is moving all the time, which is why we have dredging,” Casseau said. Because of that, the depth of the navigation channel is always fluctuating.

“The gauge, however, is static because it’s measured from a point on the land,” she said.

If low water conditions were to threaten river navigation, the Corps of Engineers is able to augment the river level with the region’s reservoir system.

“Carlyle Lake, Shelbyville Lake, Mark Twain Lake and Rend Lake are all upstream of Cape,” she said. “Those lakes are for water control management, and we know exactly how long it takes for a drop of water to leave those reservoirs and hit Cape Girardeau.”

The forecast 10.3-foot river stage later this month at Cape Girardeau will be about a half-foot lower than this year’s previous low-water mark of 10.96 feet recorded on the Cape Girardeau gauge Oct. 18. It will also be the lowest measurement since Feb. 10, 2018, when the stage was recorded at 9.03 feet.

The lowest reading on the Cape Girardeau gauge in the past decade was Oct. 14, 2012, when the river stage was measured at 4.86 feet.

According to National Weather Service records, the lowest stages ever recorded at Cape Girardeau were 0.6 feet Jan. 15, 1909, 0.8 feet measured Feb. 1, 1902, and 1 foot recorded Dec. 27, 1897.

The Mississippi River is at a low point as seen in Cape Girardeau on Thursday, Dec. 3, 2020.Sarah Yenesel ~ sarahy@semissourian.com

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