There is all sorts of controversy as to what a waterfall is. Is it a block, a fan or a horsetail? How about water volume? How much of a drop does it have to have? The term gets stretched a bit the nearer you get to sea level. Since it has been found that waterfalls emit negative ions which offset our stressful positive ions I have found a simple answer. A waterfall is a creek, stream or river with enough fall to generate those good feeling negative ions.