A pond is a body of standing water, either natural or man-made, that is usually smaller than a lake. A wide variety of man-made bodies of water are classified as ponds, including water gardens designed for aesthetic ornamentation, fish ponds designed for commercial fish breeding, and solar ponds designed to store thermal energy. Ponds and lakes are distinguished from streams via current speed. While currents in streams are easily observed, ponds and lakes possess thermally driven micro-currents and moderate wind driven currents. These features distinguish a pond from many other aquatic terrain features, such as stream pools and tide pools.
Humans also make ponds. A wide variety of man-made bodies of water are classified as ponds. Some ponds are created specifically for habitat restoration, including water treatment. Others, like water gardens, water features and koi ponds are designed for aesthetic ornamentation as landscape or architectural features. Fish ponds are designed for commercial fish breeding, and solar ponds designed to store thermal energy.
Standing bodies of water such as puddles, ponds, and lakes are often categorized separately from flowing water courses, such as a brook, creek, stream or river.
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Ponds can result from a wide range of natural processes. 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. Rivers often leave behind ponds in natural flood plains after spring flooding, and these can be very important to breeding fish, particularly in large river systems like the Amazon. Retreating glaciers can leave behind landscapes filled with small depressions, each developing its own pond; an example is the Prairie Pothole Region of North America. Many areas of landscape contain small depressions which form temporary ponds after spring snow melt, or during rainy seasons; these are called vernal ponds, and may be important sites for amphibian breeding. Some ponds are created by animals. Beaver ponds are the best known example, but alligators also excavate ponds as well. In landscapes with organic soils, fires can also create depressions during periods of drought; these become open water when normal water levels return.
