Mississippi River barge operators and shipping groups on Tuesday asked U.S. President Barack Obama to declare a state of emergency on the river and direct the Army Corps of Engineers to keep the drought-lowered waterway open to commercial traffic to avert an “economic catastrophe.”

Water on the Mississippi River along the busy stretch from St. Louis to Cairo, Illinois was expected to recede to record-low levels by mid-December, effectively halting the flow of barges that carry billions of dollars worth of grain, coal, steel, fuel and other products.

In a letter to the White House and the Federal Emergency Management Agency, the American Waterways Operators, the Waterways Council, and 16 other groups asked that the president order the Army Corps to immediately remove river-bottom rock at two locations, which posed a risk to boats during low water conditions.