Young Red Haired Girl Outside In The Nature At 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.