Wetland Types
As per the Ramsar Convention, a wetland is defined as ‘areas of marsh, fen, peatland or water, whether natural or artificial, permanent or temporary, with water that is static or flowing, fresh, brackish or salt, including areas of marine water the depth of which at low tides does not exceed six meters’. In addition, to protect coherent sites, Article 2.1 of the Convention provides that ‘wetlands may include riparian and coastal zones adjacent to the wetlands, and islands or bodies of marine water deeper than six meters at low tide lying within the wetlands.’
There exist marine and coastal wetlands such as open coasts, coral reefs, estuaries, tidal flats, mangroves and coastal lagoons; Inland wetlands such as permanent and seasonal rivers, inland deltas and floodplains, permanent and seasonal lakes and ponds, marshes, freshwater swamps and peatlands as well as Human-made wetlands such as reservoirs, barrages and dams, aquaculture ponds, excavations and burrow pits, wastewater treatment ponds, irrigation canals, ditches, irrigation ponds and rice fields. Often these wetland types are interlinked hydrologically and ecologically, merging into one another and the larger landscapes. Wetlands should, therefore, be considered as part of the river basin or coastal zone.
Major Wetland types
Human – made wetlands
These are wetlands built for a purpose, such as storing water for irrigation and drinking, or for producing fish or for recreation. Reservoirs, aquaculture ponds, salt pans, dams, barrages, and impoundments are some examples of human-made wetlands.
Lakes
Lakes and ponds (also known as lentic systems) are a diverse set of inland freshwater habitats that exist across the globe and provide essential resources and habitats for both terrestrial and aquatic organisms.
River Floodplains
These are lands adjacent to river or stream which is subject to periodic inundation by water over-topping the channel. Yamuna floodplains are the primary source of water for Delhi.
Ox-bow Lakes
Oxbows are formed when the meander of a river is cut off due to silt deposition, or river changing course, isolating a crescent-shaped waterbody. The basins of Ganga and Brahmaputra rivers abound in oxbows. In Mahanadi Delta, Ansupa is an oxbow located at delta apex.
Marshes
These are dominated by herbaceous plants and are sustained by water sources other than direct rainfall like surface runoff, groundwater or tidal flow. Kanwar Jheel (Kabar Tal) is a marsh located in floodplains of Burhi Gandak in Bihar.
Estuaries
An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river and maritime environments. A coastal lagoon is a bar-built estuary, formed when offshore barrier sand islands develop above sea-level and extend in a chain, broken by one or more inlets. Chilika is a lagoon in Odisha separated from the Bay of Bengal by a long sand berm.
Swamps
Swamps are wetlands dominated by trees. These have poor drainage and sufficient water supply to keep the ground waterlogged, and level of minerals to stimulate decay of organisms and prevent accumulation of organic materials. Mangroves are coastal swamps bordering major deltas of the country. Sunderbans, spread across India and Bangladesh is the world’s largest single contiguous mangrove swamp.
