The diminishing depths along the Mississippi River, which are forecast to reach historic lows and threaten the region's economy, could have a serious impact on local businesses that depend on the river.

On Tuesday, the river levels at St. Louis were at minus 1 feet and are estimated to reach as low as minus 5 feet in two weeks, considering the lack of significant precipitation in the forecast. The "minus" reading does not mean the river has run dry -- it's how the water level is measured.

The gauge was designed to indicate how much below or above the river is from average levels. The zero mark was established in the 1860s at St. Louis as the lowest the river had ever fallen at the time.

Mark Mestemacher, owner of barge company Ceres Barge Line in Fairmont City, is already restricting his loads. He said the U.S. Coast Guard anticipates barges will have to be reduced further within the next 15-20 days when barge drafts could be reduced from 9 feet to 8 feet.

"You're already shrinking the amount of grain that can be put on barges with lower drafts," Mestemacher said. "But we really have seen much change this past week."

In Granite City, America's Central Port Executive Director Dennis Wilmsmeyer said this has meant restricting typical barge tows from six barges wide to as little as two or three barges wide along the river. He said all barges from St. Louis and all points south downstream have been forced to lighten loads and transport less.

"It is costing the barge industry a lot of money this year," Wilmsmeyer said. "Because of that, you'll see less and less amounts of barge product going in. We'll continue to do what we can as long as we can."

Wilmsmeyer said he did not know how much another 4-foot drop in river levels could cost the metro-east economy. Mestemacher said he could not estimate the potential financial impact at this point.

"I don't know how to quantify that," he said. "It's not a good thing, I can tell you that."

A letter submitted Tuesday to President Obama from the American Waterways Operators and 17 other national organizations is requesting "immediate assistance in averting an economic catastrophe." According to the letter, an estimated $7 billion of goods that are in line to travel along the Mississippi River between December and January are threatened to be held up by the dropping river levels. That includes more than 7 million tons of agricultural products such as corn and grain worth $2.3 billion; 1.7 million tons of chemical products worth $1.8 billion; 1.3 million tons of petroleum valued of $1.3 billion; more than 700,000 tons of crude oil worth $534 million, and 3.8 million tons of coal valued at $192 million.

Mestemacher said he has been working in the barge industry since 1979 and has witnessed low water along the Mississippi before. But he said he not seen the river this low since 1988, following the historic drought during the summer of 1988. He said the river's current state could be the worst yet.

"We've had low water before, and we've had issues where we had to cut drafts, but this probably has the potential to be the most severe situation I've seen," he said. "We're not there, yet, but we're getting close."

Contact reporter Will Buss at wbuss@bnd.com or 239-2526.