A pond is a body of standing water, either natural or man-made, that is usually smaller than a lake. They may arise naturally in floodplains as part of a river system, or they may be somewhat isolated depressions (examples include vernal pools and prairie potholes). Usually they contain shallow water with marsh and aquatic plants and animals. A few animals also make ponds, including both alligators and beavers. The type of life in a pond is generally determined by a combination of factors including water level regime (particularly depth and duration of flooding) and nutrient levels, but other factors may also be important, including presence or absence of shading by trees, presence or absence of streams, effects of grazing animals, and salinity.
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.
In landscape architecture and garden design, a water feature is one or more items from a range of fountains, pools, ponds, cascades, waterfalls, and streams. Before the 18th century they were usually powered by gravity, though the famous Hanging Gardens of Babylon are described by Strabo as supplied by an Archimedean screw. Other examples were supplied with water using hydraulic rams.
Since the 18th century, the majority of water features have been powered by pumps. In the past, the power source was sometimes a steam engine, but in modern features it is almost always powered by electricity. There is an increasing range of innovative designs as the market becomes more established and people become more aware of alternate installation methods, such as solar power. The advantages of using solar power include environmental benefits, no electrical lines in the garden, and free energy.
Modern water features are typically self-contained, meaning that they do not require water to be plumbed in; rather water is recycled from either a pond or a hidden reservoir, also known as a sump. The sump can either be contained within the water feature, or buried underground (in the case of an outdoor water feature).
A water feature may be indoor or outdoor and can be any size, from a desk top water fountain to a large indoor waterfall that covers an entire wall in a large commercial building, and can be made from any number of materials, including stone, granite, stainless steel, resin, and glass. Most water features are electronically controlled, ranging from simple timer actuators to sophisticated computerized controls for synchronizing music to water and light animation.