The Mississippi River is close to historic lows, and barge owners are calling for help amid the looming, multibillion-dollar threat of shutting river transport in December.

A sustained drought for most of this year coming on the back of a light snowpack last winter has taken the Mississippi River to about a foot below its gage zero at St. Louis, a level last seen during the drought of 1988.

The drought has left the Midwest parched, and scientists have started to indicate that the prolonged dry season is one of the very real effects of climate change. In December, according to the Army Corps of Engineers, the river is expected to drop even lower -- the effect of reduced water flow after the Gavins Point Dam is closed to preserve levels in the Missouri. This could make waters in the key midsection of the Mississippi, between St. Louis and Cairo, Ill., unnavigable.

"We estimate that $7 billion of cargo will stop moving on the Mississippi River if the 9-foot channel cannot be maintained," said Craig Philip, chief executive of Ingram Barge Co. and member of both American Waterways Operators and the Waterways Council.

The Army Corps is responsible for maintaining the 9-foot channel through the river. It was built in the 1930s using a system of pools, locks and dams that keeps water levels at an easily navigable 9-foot depth. The corps has been working for almost a year to keep the channel open.

Workers have built river training structures called rock dikes. These blunt-nosed, arch-shaped limestone structures use the river's energy to sweep sediment out of the navigation channel. The corps has also been dredging to remove sediment since the beginning of July this year, a month earlier than it would normally begin dredging operations.

Despite these measures, the river has continued to sink. In late summer, barge operators, the Army Corps and the Coast Guard made a collective decision to allow only 9-foot drafts to ply the river instead of 12-foot drafts.

Looking for a presidential declaration

"Losing even 1 inch of draft is a significant loss. Thirty-six inches is a lot," said Ann McCulloch, director of public affairs and communication at American Waterways Operators.

The prospect of further reducing barge tonnage or, worse, having the river closed for trade has the industry in jitters.

The inland waterways system carries about 600 million tons of freight worth about $200 billion. The industry body estimates that 5 million barrels of domestic crude oil would need to be replaced if the Mississippi is closed in December and January. The delivery of 3.8 million tons of coal and 300 million bushels of grain would be delayed.

About 60 percent of U.S. grain exports are transported through the Mississippi. The price of grain to be exported from the Gulf of Mexico spiked over apprehension that this critical conduit would be closed, according to a Reuters report last week that found corn and soy prices surged in anticipation of choked grain transport from December onward.

Anxious industry players are asking for a presidential declaration to give the Army Corps more teeth to tackle the problem, Philip said.

Right now, the corps can take only specific action on specific triggers. The winter freeze-up in the headwater regions is one such trigger. Following the freeze, the corps has begun releasing water stores in six Mississippi headwater reservoirs. This will give the midsection a much-needed 3- to 6-inch bump in its levels.

But the corps will have to reduce flows from the Missouri to a meager 12,000 cubic feet per second from December through the end of February. The average outflow at this time of the year is 17,000 cfs. The mid- and lower Mississippi will begin to feel the impact of this cutback in December.

'We've got to have rain'

The prospect has raised such alarm that Sens. Roy Blunt (R-Mo.) and Tom Harkin (D-Iowa) and 13 other lawmakers from river states last week wrote a letter to the Army Corps requesting a delay in impounding Missouri's waters.

"If the river channel is not maintained, there will be a loss of jobs, income to many businesses and farmers, and an adverse impact to the economy of the region as a whole," they wrote.

Another area of concern is the presence of rock pinnacles, especially in the Thebes, Ill., region.

"The rocks are going to be a controlling factor with barges moving through the river," said Michael Petersen, chief of public affairs for the St. Louis District of the Army Corps. Barges may not only be grounded in shallow waters; they could be torn apart.

Senators have also asked that blasting to remove the rocks, which is scheduled for February, be expedited.

But that's easier said than done. "It's not likely because this is the kind of contract that normally takes a year to put together and we're moving it in a few months," Petersen said. "People have to remember that if we are going to be blasting in the river, that's going to interfere with commerce as well, and it's better to wait for the harvest to get done and do it in February."

With a number of short-term measures in play, Maj. Gen. John Peabody, commander of the Mississippi Valley division of the corps, has also called for a long-term plan.

"We have to start thinking that we may not have the water we're accustomed to for an extended period of time, and that means we have to husband our resources for when the situation gets truly dire, and in my personal estimate we are not there yet," he said.

Being prepared for the worst but hoping for the best may yet be the best motto for the Mississippi. Peabody said: "We've got to have rain, and that's the critical variable. And that's what all of us should be hoping and praying for."