Blonde Girl Outside In The Pond

Even among organizations and researchers who distinguish lakes from ponds by size alone, there is no universally recognised standard for the maximum size of a pond. The international Ramsar wetland convention sets the upper limit for pond size as 8 hectares (19.768 acres), but biologists have not universally adopted this convention. Researchers for the British charity Pond Conservation have defined a pond to be 'a man-made or natural waterbody which is between 1 m2 and 20,000 m2 in area (~2 ha or ~5 acres), which holds water for four months of the year or more.' Other European biologists have set the upper size limit at 5 ha (12.355 acres). In North America, even larger bodies of water have been called ponds; for example, Walden Pond in Concord, Massachusetts measures 61 acres (~25 ha).
Formation
Ponds can result from a wide range of natural processes, although in many parts of the world these are now severely constrained by human activity. Any depression in the ground which collects and retains a sufficient amount of precipitation can be considered a pond, and such depressions can be formed by a variety of geological and ecological events.