"The industry is really in a difficult position right now," Calhoun said. "It's very much a dicey and day-to-day situation."
Nashville, Tenn.-based Ingram Barge — the nation's biggest carrier on the inland U.S. waterway system — also plans to cut drafts to 8 feet for barges traveling north of Cairo, a company spokesman said.
The severity of the issue surfaced Monday, when an 18-barge tow ran aground on a submerged sandbar at a curve south of Memphis, Tenn. Refloating that barge took some 20 hours, causing a backup of 12 northbound vessels and twice that number headed downriver, the Coast Guard said.
"The low river definitely is affecting the way mariners are transiting the river," said Lt. Ryan Gomez of the Coast Guard's Memphis office. "It is a concern right now."
River shipping trade groups have warned of a potential economic disaster if river traffic is restricted or shut down for an extended period.
Last week, several senators whose states border the Mississippi River met with Army Assistant Secretary Jo-Ellen Darcy, urging her to take two steps to ease concerns: Cut down on the amount of water held back on the upper Missouri River; and expedite removal of massive rock formations in the Mississippi River near two southern Illinois towns, formations that could scrape barges in periods of extreme drought.
Current plans call for explosives to be used in February to blow up the rocks, but Army Corps spokesman Mike Petersen in St. Louis said Wednesday that the agency has expedited soliciting bids for the work with hopes of having a contractor hired as early as next month. The Corps also has promised the senators a response to their water flow request by later this week.