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Wetlands in India: Their Importance and hydrologic alteration as threat from urbanization

Content: Introduction > Wetlands in India: Current Scenario > Wetland Services > Urban Water Crisis and Altered Hydrology Cycle (Case study: Chilika Lake) > Concerns (Case study: Sonbhadra) > Conclusion


Wetlands as the name suggest is any land which is wet or contain water. There has been much definition for wetlands but none can be said perfect definition. Since years, the most common definition used by scientific texts is, wetlands are lands transitional between terrestrial and aquatic eco-systems where the water table is usually at or near the surface or the land is covered by shallow water (Mitch and Gosselink, 1986). However a more clear and detailed definition can be found of that of Ramsar Convention, entered into force 1975  as ‘areas of marsh, fen, peat, land 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 tide does not exceed six meters’. In addition to that, the Convention Article 2.1 provides that wetlands ‘may incorporate 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.’ 

Wetlands in India: Current Scenario

Total area under wetland in the country is estimated as 15.260 MHa by NWIA (National Wetland Inventory and Assessment), 2011 which accounts for 4.63% of the geographical area. Excluding rivers and streams the total wetland area is estimated as 10 MHa. A detailed data of the NWIA report is as follows: 

Classification of Wetlands in India

State-wise distribution of wetlands showed that Lakshadweep has 96.12% of geographic area under wetlands followed by Andaman and Nicobar Islands (18.52%), Daman and Diu (18.46%) and Gujarat (17.56%), have the highest extent of wetlands. Puducherry (12.88%), West Bengal (12.48%), Assam (9.74%), Tamil Nadu (6.92%), Goa (5.76%), Andhra Pradesh (5.26%), and Uttar Pradesh (5.16%) are wetland rich states. The least extents(less than 1.5 % of the state geographic area) have been observed in Mizoram (0.66%) followed by Haryana (0.86%), Delhi (0.93%), Sikkim (1.05%), Nagaland (1.30%), and Meghalaya (1.34%).

Inland – Natural WetlandsTamil Nadu has highest number of lakes (4369) followed by Uttar Pradesh (3684) and West Bengal (1327). Ox-bow lakes/Cut-off meanders are observed in Uttar Pradesh, West Bengal, Bihar, Assam and Orissa. Large number of riverine wetlands exists in Uttar Pradesh, West Bengal, Bihar, Assam and Jammu & Kashmir.

Inland – Man-made Wetlands: Andhra Pradesh has highest number of reservoirs (4527) followed by Madhya Pradesh (2005), Uttar Pradesh (1608), Orissa (1379) and Gujarat (1213). Details are summarised below. Large number of Tanks/ponds exists in Tamil nadu, Maharashtra, Madhya Pradesh, Andhra Pradesh, Rajasthan and Karnataka.

Small wetlands ( less than 2.25 ha) : There are 555557 such wetlands exists in the country. West Bengal has highest number of small wetlands (138707), followed by Uttar Pradesh, Orissa, Madhya Pradesh, and Rajasthan. 

Mangrove along Kerala coast. Mangroves are habitats for a numerous aquatic species and protect coastal lands from erosion.

Wetland Services

Without any visible utility to mankind they were used to be considered as wasteland. But with progress of ecology and ecologists, slowly the topic of wetland conservation caught the pace. Wetlands are not only the most productive eco system on earth and support numerous unique flora and fauna but is also directly linked with livelihood and food security in addition to much economic benefits. A much details about the wetland services are discussed as follows:

i) Water Storage: Wetlands serve as natural rainwater harvesting sites by collecting the precious rainwater within it. Water supply to many big cities are done by wetlands alone. Mumbai is an example of such cities where the entire water supply is from wetlands in the vicinity like Modak Sagar, Tansa lake, Vihar lake, Tulsi lake, Upper Vaitarana and Bhatsa. 

ii) Storm protection and flood mitigation: Wetlands in close vicinity of rivers also act as buffers to control flood and river flow. When the level of river rises, water flows into the wetlands and similarly when river water level decreases, water from these wetlands gushes into the river thus maintaining the average flow of the river.

iii) Shoreline stabilisation and erosion control: Lagoons and backwater plays a very important role in stabilizing the coastal borders. Mangroves are mostly found in such eco systems which not only protects the land from speedy waves but protects from cyclones too. In 2004 Tsunami, the coasts with good mangrove vegetation were least affected. 

iv) Groundwater recharge: Wetlands act as natural rainwater recharging zones. Watre stored in the wetland percolates slowly in the aquifers. Udaipur in Rajasthan is a wonderful example where around 2500 man-made lakes has solved the region’s water problem to a great extent.

v) Groundwater discharge: Wetlands not only act as groundwater recharging sites, sometime sthey can even provide easy access to groundwater by converting it into surface water.

vi) Water purification: Every water body has a self cleaning system. Many aquatic flora and micro fauna present in wetlands are found to be effective in treating water with high coli form percentage as well. Many species of algae and plants have remarkable capacity of accumulating heavy metals in their mucilage and leaves and are known as hyper-accumulators. 

vii) Sediment and nutrition retention: During rainfall and floods, much sediments and nutrients are wasted with run off. A nearby wetland not only control run off but also retain the sediments and nutrients within it. The same things also applies with pollutants and thus help the riverine ecosystems to get affected.

viii) Stabilisation of local climatic condition: Wetlands play a great role in regulating local climate particularly temperature and moisture. The phytoplankton community are very good carbon sequesters and absorbs carbon dioxide much faster than terrestrial plants. Wetlands are thus also considered as local carbon sinks. 

ix) Biodiversity: The most productive ecosystem, wetlands harbor a great variety of animals and plants. It is a paradise of bird watchers and many birds find hostage in wetlands all around the world. There are many wildlife sanctuaries like Keoladeo Ghana Wildlife Sanctuary in Rajasthan, Point Calimere Wildlife Sanctuary in Tamil Nadu Harike Pattan Wildlife Sanctuary in Punjab which are protected for their rich biodiversity. Of the 310 wetland bird species in India, 51 (ca. 16%) are Threatened of which 34 are Globally Threatened (four Critical, seven Endangered, 23 Vulnerable); 16 Near Threatened (NT) and one Data Deficient (DD). Of the 51 Threatened species, 39 show a declining population trend, while three are increasing, five are stable, and the trends of three species are indeterminate. The remaining one species, Pink-headed Duck Rhodonessa caryophyllacea globally threatened, has probably disappeared from India. Apart from this, fisheries provide great economic support to people and ensure livelihood of millions.

Corals at Kanyakumari, India. Coral reefs are also known as 'Rainforests of Ocean' as they are shelters for numeorus fish species and other animals. Corals are now threatened due to pollution and global warming. Lakshadweep Island is also known as ‘coral island’. Loss of coral reefs around Lakshadweep also resulted into extinction of several fish species from there

Urban Water Crisis and Altered Hydrology Cycle

As we all know, earth has 70% of area as water. Out of this, 97.5% is saline and unusable or very costly to purify it. Out of remaining 2.5%, 95% of it is in form of glaciers and ice structures which are inaccessible. So we have less than 0.5% of water which is under direct use which includes water from rivers, wetlands and aquifers. As evident, our river waters are either degrading due to pollution, industrial contamination and other uncontrollable activities related to religion or urbanization, creation of dams also affected the water availability in regions downstream. A fine example is seen of river Yamuna in Delhi, which is now known as ‘Dead River’ which was once a lifeline of the capital and used to host a large number of migratory birds. The problem of siltation is now one of the major problems of almost all rivers. A worse situation can be seen of the holiest river Ganges which is also believed to contain purest water in country once; the fact is that, it will be not unjust to declare it the most polluted river of the country. 

Places like Delhi where water table used to be around 30 feet before independence has shockingly dropped to more than 300 feet in many areas. This case is now common with almost all developing cities. The major reason is of course rise in population which creates intense water demand but another reason is non-recharging of groundwater. Due to rapid concretization and cementation of ground surface, we are not allowing the rainwater to percolate inside the ground which resulted in altered hydrological cycle. The water which was meant to recharge aquifers now reaches the river as surface run off or man-made drains. This not just lowers the natural water table but also degrading the quality of river water. In case of wetlands, alteration of wetland hydrology can change the soil chemistry and the plant and animal community. Alteration which reduces or increases the natural amount of water entering a wetland or the period of saturation and inundation can, in time, cause the ecosystem to change to an upland system or, conversely, to a riverine or lacustrine system. Due to this another problem which is occurring now days is coastal subsidence. Land subsidence also allows saltwater intrusion into freshwater wetlands and causes shifts in the plant and animal community. Saltwater intrusion and the subsequent modification of wetlands habitat threaten the fishery industry as well. 

Chilika Lake: A case study
Chilika lake is the largest coastal lagoon in Asia and world’s second largest lagoon in the world. The lagoon is the largest migratory ground in India with nearly 160 species of birds and severe endangered species, Irrawady dolphins being the most famous. The lake was recorded as Ramsar site in 1981 but was listed in Monteux record in 1993. Montreux record is a list of wetlands of international importance where changes in ecological character have occurred, are occurring, or are likely to occur as a result of technological development, pollution or other human interference. It is maintained as part of the Ramsar list. Siltation from upstream alongwith decrease in salinity and excessive growth of invasive species affected the surface areas, wildlife and fishery resources of the wetland to a great extent. Chilika Development Authority was set up by Indian government in order to revive the wetland. The project involved nearly Rs. 600 million from different sources and a wide support from various NGOs. and in 2002, it was removed from Montreux record. It was the first wetland in Asia to be removed from Montreux record. Chilika Development Authority also received Ramsar Wetland Conservation Award for outstanding achievement in the field of restoration and wise use of wetlands and effective participation of local communities in these activities. 

 Fishermen during their morning catch at Chilika Lake, Odisha


Due to cemented roads everywhere, the rainwater becomes incapable to reach water table, the runoff accumulates with itself many sediments, contaminants, pollutants, mud, pesticides, fertilizers, organic matter, animal wastes, heavy metals, hydrocarbons, road salts and debris with them and finally reach the river or nearby large wetlands. This not only decrease dissolved oxygen in water but also results in siltation and altered physiological and chemical parameters of water making it unfit for not just human beings but affect survival of other species too. This is one of the major concerns. From river this water drains off in the ocean. This is also a process where so precious freshwater resource is converted into saltwater. This is not a small problem as it seems to read here. 

As runoff moves over warmed impervious surfaces, the water temperature rises and dissolved oxygen content of the runoff water decreases. Increased water temperature, as well as the lower dissolved oxygen levels, can cause stress or mortality of aquatic organisms. Rising water temperatures can trigger a release of nutrients from wetland sediment. For example, as temperature rises, sediments release phosphorus at an exponential rate. Thus water temperature increases can lead to eutrophication.

Houseboats at Dal Lake, Kashmir. A major tourist attraction of Srinagar, it is an example of wetland badly affected by the tourism.

Urban and industrial storm water, sludge, and wastewater treatment plant effluent, rich in nitrogen and phosphorus, can lead to algal blooms in estuaries. Algal blooms deplete dissolved oxygen, leading to mortality of benthic organisms. Some algae are also toxic to aquatic life. Industrial sludges also contain a substantial concentration of heavy metals which can lead to many health implications. 

Sonbhadra: A case study
Sonbhadra is a district in southern tip of Uttar Prdesh adjoining district Singrauli in Madhya Pradesh. Sonbhadra and SIngrauli together is called ‘power capital’ of India. Singrauli has the country’s largest coal field and 9 coal-fired thermal power plants equivalent to 10% of India’s installed power capacity. In 1991, the Central Pollution Control Board identified Sonbhadra and Singrauli as critically polluted area. Rihand dam on Renu river also known as Goving Ballabh Pant Sagar is the main waterbody in the region which also receives a huge amount of industrial effluents from chemical factories and aluminum smelters situated nearby. In an independent study by Vanvasi Seva Asram in 2009 it was claimed that the water discharged into Dongiya nullah from Kanoria chemicals, a caustic soda manufacturing company had mercury levels 15.3 µg/l against permissible limit of 10 µg/l. Also, the fly ash from thermal power units were found to be dumped into the river or leaching from fly ash ponds.4 Another study done by Delhi based NGO Centre for Science and Environment found 0.447 ppm of methyl mercury from fish samples from Dongiya nullah almost twice the limit set by Food Safety and Standards Authority of India. The water from hand pump was found to be 0.026 ppm, 26 times the standard set up by BIS at 0.001 ppm. 58% of human hairs were found contained with mercury at 7.39 ppm highest being 31.3 ppm as compared to 6 ppm as safety standard by Health Canada. 84% of blood samples had average mercury 34.3 ppb, 6 times more than safe standard set by US Environmental Protection agency.5

Another serious and recent concern to wetlands is the landfills. Due to limited area and increasing population, the cities face great problems with disposal of waste. Landfills are designated areas where waste from different parts of the cities is dumped. Landfill construction may alter the hydrology of nearby wetlands. Leachate from solid waste landfills often has high biological oxygen demand (BOD), and ammonium, iron, and manganese in concentrations that are toxic to plant and animal life. 

A wetland in Badarpur, Delhi. This wetland was to convert into a landfill for Delhi. Saving this wetland also turned out to be a turning point in life of Debaadityo, his first campaign as an environment activist. This picture was taken way back in 7th February, 2008.  

As a result of disturbance and habitat degradation, wetlands can be invaded by aggressive, highly-tolerant, non-native vegetation. The canals of Chambal commanded area in rajasthan and Madhya Pradesh and Bhakra Nangal in Himachal Pradesh and Punjab have been greatly slowed by the aquatic weeds. Weeds like Eichhornia crasipes, Salvinia molesta, Chara sp., Nitella spp., Potamogeton sp., Nelumbo nucifera, Hydrilla verticillata are some of the most concerned. It is estimated that there are 140 aquatic weeds in India. (Varshney et. al, 2008)


Wetlands are the ultimate groundwater recharging areas which not only helps collection of rainwater and making it available to percolation but its role in cleaning the water, nutrient retention, flood protection and erosion control is also very important. Hence, they are also known as ‘kidneys of landscape’. They are highly rich in biodiversity and are also linked to food and water security of the country. Despite all the important functions and service they provide, wetlands in India are indeed facing a great threat from urbanization and growing population. It is a herculean task to protect the existing wetlands from different pressures. Increased public awareness, collaborative scientific and public efforts along with a great political will is needed to bring about the exemplar shift in conserving this beautiful architectural wonders.

(Article Written for World Wetland Day by Debaadityo Sinha)

References for Further Reading

  1. Ramsar Official Website.
  2. Information Brochure on National Wetland Inventory and assessment 2011, Ministry of Environment and Forests, Govt. of India
  3. Kumar, A., Tak, P.C. & Sati, J.P. 2006. Residential, population and conservation status of Indian wetland birds. Waterbirds around the world. Eds. G.C. Boere, C.A. Galbraith & D.A. Stroud. The Stationery Office, Edinburgh, UK. p. 308.
  4. Mercury in air, water | Down to Earth
  5. CSE Study: Mercury Pollution in Sonbhadra District of Uttar Pradesh and its Health Impacts, Centre for Science and Environment, Down to Earth, 2012, 
  6. Varshney, Jay.G., Sushilkumar and Mishra, J.S., 2008. Current Status of Aquatic Weeds and Their Management in India. Proceedings of Taal 2007: 12th World Lake Conference: 1039-1045
  7. William J. Mitsch, James G. Gosselink, Wetlands. Van Nostrand Reinhold Company, 1986.

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