Reuters / Commercial barge traffic on a critical stretch of the Mississippi River south of St. Louis may be severely restricted or halted entirely next month as drought conservation measures stem the inflow of water from the Missouri River.

With the worst U.S. drought in 56 years sapping the reservoirs that feed the Missouri River, the flow of water from Gavins Point Dam will be reduced later this month.

“When we did our Sept. 1 storage check we saw that water levels had decreased (from midsummer) and we made the decision that we had to take drought conservation measures during the winter,” said a spokeswoman for the Army Corps of Engineers.

The Missouri River normally accounts for about 60 per cent of the water in the Mississippi River between St. Louis and Cairo, Illinois, a key stretch of the major grain-shipping waterway between the Midwest and export terminals at the Gulf Coast. About 55 to 65 per cent of U.S. corn, soybean and wheat shipments exit the country via the Gulf.

If rains don’t come soon, restrictions may be placed on tow sizes and drafts, possibly sidelining many of the boats that tow barges. Barge loads could also be reduced, which would drive up freight costs.