Mississippi River Memphis -Zero Stage 10-13-2011 (10), a photo by joespake on Flickr.
A southbound towboat about to pass the mouth of Wolf River, at Zero Feet river stage. Merely a stream now, in May, water from the swollen Mississippi backed up into the Wolf River for miles.
Zero stage does not mean the river is empty. It is a benchmark for the lowest river level to expect. The record low water at Memphis is -10.7 feet.