The U.S. Coast Guard said on Monday that 97 vessels were stranded by low water on the Mississippi River near Greenville, Miss., after it closed an 11-mile stretch of the drought-parched waterway for dredging and to replace missing navigation buoys.

The worst U.S. drought in 56 years has left the river there at its lowest point since 1988, a year when a similarly dire drought also stalled commercial traffic on the major shipping waterway.

Further north, dredging operations near St. Louis were halting river traffic for 12 hours at a time as the U.S. Army Corps of Engineers worked to keep a shipping lane wide enough and deep enough for commercial barge tows hauling everything from grain and fertilizer to steel and coal, industry sources said.