Pond
A pond is a small, still, land-based
Ponds are typically shallow water bodies with varying abundances of
Ponds are frequently man made or expanded beyond their original depths and bounds by
Classification
The technical distinction between a pond and a lake has not been universally standardized. Limnologists and freshwater biologists have proposed formal definitions for pond, in part to include 'bodies of water where light penetrates to the bottom of the waterbody,' 'bodies of water shallow enough for rooted water plants to grow throughout,' and 'bodies of water which lack wave action on the shoreline.' Each of these definitions are difficult to measure or verify in practice and are of limited practical use, and are mostly not now used. Accordingly, some organizations and researchers have settled on technical definitions of pond and lake that rely on size alone.[6]
Some regions of the United States define a pond as a body of water with a surface area of less than 10 acres (4.0 ha). Minnesota, known as the "land of 10,000 lakes", is commonly said to distinguish lakes from ponds, bogs and other water features by this definition,[7] but also says that a lake is distinguished primarily by wave action reaching the shore.[8] Even among organizations and researchers who distinguish lakes from ponds by size alone, there is no universally recognized standard for the maximum size of a pond. The international Ramsar wetland convention sets the upper limit for pond size as 8 hectares (80,000 m2; 20 acres).[9] Researchers for the British charity Pond Conservation (now called Freshwater Habitats Trust) have defined a pond to be 'a man-made or natural waterbody that is between 1 m2 (0.00010 hectares; 0.00025 acres) and 20,000 m2 (2.0 hectares; 4.9 acres) in area, which holds water for four months of the year or more.' Other European biologists have set the upper size limit at 5 hectares (50,000 m2; 12 acres).[10]
In North America, even larger bodies of water have been called ponds; for example,
In practice, a body of water is called a pond or a lake on an individual basis, as conventions change from place to place and over time. In origin, a pond is a variant form of the word pound, meaning a confining enclosure.[12] In earlier times, ponds were artificial and utilitarian, as stew ponds, mill ponds and so on. The significance of this feature seems, in some cases, to have been lost when the word was carried abroad with emigrants. However, some parts of New England contain "ponds" that are actually the size of a small lake when compared to other countries. In the United States, natural pools are often called ponds. Ponds for a specific purpose keep the adjective, such as "stock pond", used for watering livestock. The term is also used for temporary accumulation of water from surface runoff (ponded water).
There are various regional names for naturally occurring ponds. In Scotland, one of the terms is lochan, which may also apply to a large body of water such as a lake. In the South Western parts of North American, lakes or ponds that are temporary and often dried up for most parts of the year are called playas.[13] These playas are simply shallow depressions in dry areas that may only fill with water on certain occasion like excess local drainage, groundwater seeping, or rain.
Formation
Any depression in the ground which collects and retains a sufficient amount of water can be considered a pond, and such, can be formed by a variety of geological, ecological, and human terraforming events.
Natural ponds are those caused by environmental occurrences. These can vary from glacial, volcanic, fluvial, or even tectonic events. Since the Pleistocene epoch, glacial processes have created most of the Northern hemispheric ponds; an example is the
Manmade ponds are those created by human intervention for the sake of the local environment, industrial settings, or for recreational/ornamental use.
Uses
Many ecosystems are linked by water and ponds have been found to hold a greater biodiversity of species than larger freshwater lakes or river systems.[23] As such, ponds are habitats for many varieties of organisms including plants, amphibians, fish, reptiles, waterfowl, insects and even some mammals. Ponds are used for breeding grounds for these species but also as shelter and even drinking/feeding locations for other wildlife.[24][25] Aquaculture practices lean heavily on artificial ponds in order to grow and care for many different type of fish either for human consumption, research, species conservation or recreational sport.
In agriculture practices, treatment ponds can be created to reduce nutrient runoff from reaching local streams or groundwater storages. Pollutants that enter ponds can often be mitigated by natural sedimentation and other biological and chemical activities within the water. As such, waste stabilization ponds are becoming popular low-cost methods for general wastewater treatment. They may also provide irrigation reservoirs for struggling farms during times of drought.
As urbanization continues to spread, retention ponds are becoming more common in new housing developments. These ponds reduce the risk of flooding and erosion damage from excess storm water runoff in local communities.[26]
Experimental ponds are used to test hypotheses in the fields of environmental science, chemistry, aquatic biology, and limnology.[27]
Some ponds are the life blood of many small villages in arid countries such as those in sub-Saharan Africa where bathing, sanitation, fishing, socialization, and rituals are held.
In Nepal artificial ponds were essential elements of the ancient drinking water supply system. These ponds were fed with rainwater, water coming in through canals, their own springs, or a combination of these sources. They were designed to retain the water, while at the same time letting some water seep away to feed the local aquifers.[30]
Pond biodiversity
Often, the entire margin of the pond is fringed by
Opposite to long standing ponds are
Often groups of ponds in a given landscape - so called 'pondscapes' - offer especially high biodiversity benefits compared to single ponds. A group of ponds provides a higher degree of habitat complexity and habitat connectivity.[31][32]
Stratification
Many ponds undergo a regular yearly process in the same matter as larger lakes if they are deep enough and/or protected from the wind. Abiotic factors such as UV radiation, general temperature, wind speed, water density, and even size, all have important roles to play when it comes to the seasonal effects on lakes and ponds.[33] Spring overturn, summer stratification, autumn turnover, and an inverse winter stratification, ponds adjust their stratification or their vertical zonation of temperature due to these influences. These environmental factors affect pond circulation and temperature gradients within the water itself producing distant layers; the epilimnion, metalimnion, and hypolimnion.[18]
Each zone has varied traits that sustain or harm specific organisms and biotic interactions below the surface depending on the season. Winter surface ice begins to melt in the Spring. This allows the water column to begin mixing thanks to solar convection and wind velocity. As the pond mixes, an overall constant temperature is reached. As temperatures increase through the summer, thermal stratification takes place. Summer stratification allows for the epilimnion to be mixed by winds, keeping a consistent warm temperature throughout this zone. Here, photosynthesis and primary production flourishes. However, those species that need cooler water with higher dissolved oxygen concentrations will favor the lower metalimnion or hypolimnion. Air temperature drops as fall approaches and a deep mixing layer occurs. Autumn turnover results in isothermal lakes with high levels of dissolved oxygen as the water reaches an average colder temperature. Finally, winter stratification occurs inversely to summer stratification as surface ice begins to form yet again. This ice cover remains until solar radiation and convection return in the spring.
Due to this constant change in vertical zonation, seasonal stratification causes habitats to grow and shrink accordingly. Certain species are bound to these distinct layers of the water column where they can thrive and survive with the best efficiency possible.
For more information regarding seasonal thermal stratification of ponds and lakes, please look at "Lake Stratification".
Conservation and management
Ponds provide not only environmental values, but practical benefits to society. One increasingly crucial benefit that ponds provide is their ability to act as greenhouse gas sinks. Most natural lakes and ponds are greenhouse gas sources and aid in the
Some farm ponds are not used for runoff control but rather for livestock like
Ponds, depending on their orientation and size, can spread their wetland habitats into the local riparian zones or watershed boundaries. Gentle slopes of land into ponds provides an expanse of habitat for wetland plants and wet meadows to expand beyond the limitation of the pond.[38] However, the construction of retaining walls, lawns, and other urbanized developments can severely degrade the range of pond habitats and the longevity of the pond itself. Roads and highways act in the same manor, but they also interfere with amphibians and turtles that migrate to and from ponds as part of their annual breeding cycle and should be kept as far away from established ponds as possible.[39] Because of these factors, gently sloping shorelines with broad expanses of wetland plants not only provide the best conditions for wildlife, but they help protect water quality from sources in the surrounding landscapes. It is also beneficial to allow water levels to fall each year during drier periods in order to re-establish these gentile shorelines.[39]
In landscapes where ponds are artificially constructed, they are done so to provide wildlife viewing and conservation opportunities, to treat wastewater, for sequestration and pollution containment, or for simply aesthetic purposes. For natural pond conservation and development, one way to stimulate this is with general stream and river restoration. Many small rivers and streams feed into or from local ponds within the same watershed. When these rivers and streams flood and begin to meander, large numbers of natural ponds, including vernal pools and wetlands, develop.[40]
Examples
Some notable ponds are:
- Big Pond, Nova Scotia, Canada
- Christian Pond, Wyoming, United States
- Walden Pond, Massachusetts, United States, associated with Henry David Thoreau
- Hampstead Ponds, London
- Kuttam Pokuna, Medieval artificial pond in Anuradhapura, Sri Lanka
- Rani Pokhari, 17th-century artificial pond in Kathmandu, Nepal
- Rožmberk Pond, Czech Republic
See also
- Cypress dome – Swamp dominated by pond or bald cypress
- Garden pond – Water feature in gardens
- Treatment pond – pond which is constructed to treat lightly polluted water or wastewater
- Water garden – Garden with water as a main feature
References
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- ^ a b Clegg, J. (1986). Observer's Book of Pond Life. Frederick Warne, London
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- ^ "Kettles (U.S. National Park Service)". www.nps.gov. Retrieved 16 November 2020.
- ^ "How do glaciers affect land? | National Snow and Ice Data Center". nsidc.org. Retrieved 16 November 2020.
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- ^ ISBN 978-0-511-77817-9
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- ^ "Freshwater ecosystems". Forest Research. 29 May 2018. Retrieved 16 November 2020.
- ^ "Why are ponds important?". Ghost Ponds : Resurrecting lost ponds and species to assist aquatic biodiversity conservation. 30 December 2013. Retrieved 16 November 2020.
- ^ "Why Ponds are Important to the Environment (How you can help)". Pond Informer. 31 December 2018. Retrieved 16 November 2020.
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- ^ "Water Chemistry Testing". www.ponds.org. Retrieved 16 November 2020.
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- ^ Traditional Ponds – The Water Urban-ism of Newar Civilization Archived 2021-03-22 at the Wayback Machine by Padma Sunder Joshi, Spaces Nepal, April 2018, retrieved 11 October 2019
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Further reading
- Hughes, F.M.R. (ed.). (2003). The Flooded Forest: Guidance for policy makers and river managers in Europe on the restoration of floodplain forests. FLOBAR2, Department of Geography, University of Cambridge, Cambridge, UK. 96 p.[1]
- Environment Canada. (2004). How Much Habitat is Enough? A Framework for Guiding Habitat Rehabilitation in Great Lakes Areas of Concern. 2nd ed. 81 p.[2]
- Herda DJ (2008) Zen & the Art of Pond Building Sterling Publishing Company. ISBN 978-1-4027-4274-3.
- W.H. MacKenzie and J.R. Moran (2004). Wetlands of British Columbia: A Guide to Identification. Ministry of Forests, Land Management Handbook 52.