WASHINGTON –

On one stretch of the Mississippi River, the U.S. Coast Guard has been reduced to playing traffic cop. For eight hours a day, shipping is allowed to move one way along the 290 km of river between St. Louis, Missouri, and Cairo, Illinois, depending on the hour. For the other 16 hours, boats go nowhere, because the river is closed to traffic.

The Mississippi, parched by the historic summer drought, is on the verge of reaching a new low. That could mean that tugboats pushing barges loaded with billions of dollars worth of cargo will not be able to make their way up and down the river.

Through the night, contractors for the U.S. Army Corps of Engineers remove rocks from a stretch near Thebes, Illinois, that threaten to cut boats to shreds. The corps has assured state officials, farmers and coal barons who rely on the shipping that it can maintain the 2.7-meter level it says makes navigation safe. But those who rely on the river say they are nevertheless worried.

As of Friday, National Weather Service hydrologists forecast that the river near Thebes could drop below a point that will allow barges to safely navigate with heavy cargo, forcing the coast guard to restrict weight and effectively shutting down commerce late this week, according to reports.

But the army corps assured state officials the Mississippi will remain open. Recent rain and water releases from the corps' Carlyle Lake in Illinois improved water levels for the Middle Mississippi River, the corps said.

"There's nothing pretty about this," coast guard Lt. Colin Fogarty said Friday. "We are facing a historic drought. River levels are at record lows we haven't seen since 1941. Over six weeks the army corps has dredged record amounts of the river."

But, Fogarty said, reports the Mississippi will close are as reliable as doomsday projections.

Tamara Nelson, senior director of commodities for the Illinois Farm Bureau, has faith in the corps, but is worried by the long Midwest dry spell. "Not being able to move anything on that river will be critical, a big hit," she said. "It affects tax revenues for the federal government. It affects jobs."