Record lows are still “very possible” on the Mississippi River between now and mid-September, though the river bed is a different place than the last time a major closure hampered shipping, the chief of U.S. Army Corps of Engineers’ Mississippi Valley Division said Wednesday in Vicksburg, hours before a barge traffic jam began to clear near Greenville.

“Since 1988, we’ve done a heck of a lot of work in that river to put in training structures, revetment and so forth,” said Maj. Gen. John W. Peabody, head of MVD and president of the Mississippi River Commission. “The river in general operates a lot more efficiently than it did.”

Then, the river dipped to minus 10.7 feet in Memphis and was closed for four days. Vicksburg’s stage went to minus 1.6 feet that year, which mirrored 2012 in that much of the nation was parched by a severe drought.

This year, about 60 percent of the nation is in a persistent dry spell. Stages at Vicksburg were 0.34 feet this morning, down three-tenths of a foot. In Greenville, where the Corps has dredged to free up barges largely stopped since Tuesday, the river was 7.63 feet, about the same as Wednesday morning. The stage in Memphis was minus 9.4 feet today.

Earlier today, the Coast Guard allowed 55 barges to move out of an 11-mile stretch south of Greenville after a grounded vessel was cleared from the channel, spokesman Lt. Ryan Gomez said. A 5-mile “safety zone” restricted to light loads was likely to remain in effect today as 50 barges wait to pass, Gomez said.

“It’s still an area we’re having a problem with,” Gomez said.

Stages in Vicksburg are forecast to dip to minus 0.8 feet by mid-September, according to the National Weather Service River Forecast Center. The record low is minus 7 feet, set in 1940.

Thanks to dredging, the river is generally “a little bit steeper, a little bit deeper than in 1988,” Peabody said during a pit stop between MRC’s seasonal low-water meetings to tour the Lower Mississippi River Museum and Riverfront Interpretive Site in Vicksburg, which opens to the public Friday. Once removed, silt is pushed from a 1,000-foot pipe and redistributed in the river away from the main channel. Barges twice have run aground on the Lower Mississippi south of Greenville this month despite the improvements, prompting a bottleneck the barge industry estimates is costing $10,000 a barge tow daily. He termed the traffic jam “part of the challenge.”

What happens next with shipping depends on each towboat, Peabody said.

“It really kind of depends on how skillful the pilots are at navigating these extreme lows and much tighter channels than they’re accustomed to,” he said. “It’s testing their skills — there’s no question about that.”

Dredging needs are “significant” through the rest of the year, he said. Four Corps-owned and four contract vessels are dredging the river between St. Louis and Vicksburg, including the Jadwin south of Greenville. On Friday, the Corps expects to award a $6.1 million contract to Illinois-based Great Lakes Dredge and Dock Co. to clear parts of east banks of the river starting about Sept. 7. The Butcher, a contract dredge, will work near Lake Providence, where barges have collected due to low water, until mid-September.

The Port of Vicksburg, off the main channel, is to be dredged next month. Most heavy materials have stopped moving at the port’s main support platform.

“The only thing we’re loading right now is steel coil,” said Keith Cochran, a local supervisor for Kinder Morgan Bulk Terminals, which operates the port.

In December, the Corps received $802 million in emergency money to address the river system and its tributaries after last year’s historic flood, which built up silt and sand and has made navigation more difficult than usual. About $200 million of it has gone to dredge a river in reverse mode, and it should last through year’s end, Peabody said.

“Without that money, we would be struggling,” he said. “It’s unlikely we’d be able to do as much dredging as we’re doing today.”

Both Vicksburg and Greenville were being considered as a starting point for the new dredging, the Corps has said. The MRC, a seven-member panel tasked with general improvement of navigation, flood protection and commerce on the Mississippi River system, meets next in Houma, La., on Friday.