Pond

A pond is an area filled with water, either natural or artificial, that is smaller than a lake. Ponds are small bodies of freshwater with shallow and still water, marsh, and aquatic plants.: 460  Ponds can be created by a wide variety of natural processes, or they can simply be isolated depressions filled by runoff, groundwater, or precipitation, or all three of these. They can be further divided into four zones: vegetation zone, open water, bottom mud and surface film.: 160–163  The size and depth of ponds often varies greatly with the time of year; many ponds are produced by spring flooding from rivers. Ponds may be freshwater or brackish in nature. 'Ponds' with saltwater, with a direct connection to the sea that maintains full salinity, would normally be regarded as part of the marine environment because they would not support fresh or brackish water organisms, so not really within the realm of freshwater science.