Chilka Lake

Chilika Lake is a brackish water lagoon, spread over the Puri, khordha and Ganjam districts of Odisha state on the east coast of India, at the mouth of the Daya River, flowing into the Bay of Bengal, covering an area of over . It is the biggest lake of India after Vembanad Lake. This lake is the largest coastal lagoon in India and the largest brackish water lagoon in the world after The New Caledonian barrier reef. It has been listed as a tentative UNESCO World Heritage site. It is a salt water lake.

It is the largest wintering ground for migratory birds on the Indian sub-continent. The lake is home to a number of threatened species of plants and animals.

The lake is an ecosystem with large fishery resources. It sustains more than 150,000 fisher–folk living in 132 villages on the shore and islands.

The lagoon hosts over 160 species of birds in the peak migratory season. Birds from as far as the Caspian Sea, Lake Baikal, Aral Sea and other remote parts of Russia, Kirghiz steppes of Kazakhstan, Central and southeast Asia, Ladakh and Himalayas come here. These birds travel great distances; some of them possibly travel as much as to reach Chilika Lake.

In 1981, Chilika Lake was designated the first Indian wetland of international importance under the Ramsar Convention.

According to a survey, 45 percent of the birds are terrestrial in nature, 32 percent are waterfowl, and 23 percent are waders. The lagoon is also home to 14 types of raptors. Around 152 rare and endangered Irrawaddy dolphins have also been reported. Plus, the lagoon supports about 37 species of reptiles and amphibians.

The highly productive Chilika Lagoon eco-system with its rich fishery resources sustains the livelihood for many fishermen who live in and near the lagoon. The water spread area of the lagoon ranges between during the monsoon and summer respectively. A long, narrow, outer channel connects the lagoon to the Bay of Bengal, near the village Motto. More recently a new mouth has been opened by CDA which has brought a new lease of life to the lagoon.

Microalgae, marine seaweeds, sea grasses, fish and crab also flourish in the brackish water of the Chilika Lagoon. Especially the recovery of seagrass beds in recent years is a welcoming trend which may eventually result in re-colonization of endangered dugongs.

History

Geological evidence indicates that Chilika Lake was part of the Bay of Bengal during the later stages of the Pleistocene period (1.8 million to 10,000 years BP).

Excavations were conducted by the Archaeological Survey of India at Golabai Sasan () just north of Chilika lake in Khurdha district. Golabai provides evidence of a sequence of Chilika area culture in three phases: Neolithic (c. 1600 BCE), Chalcolithic (c. 1400 BCE to c. 900 BCE) and Iron Age (c. 900 BCE to c. 800 BCE). Radiocarbon dating traced the earliest level of Golbai to 2300 BCE. The site is located on the left bank of the Malaguni River, a tributary of the Daya River, which flows into Chilika Lake. This location, which gave access to the sea via Chilika Lake, gives strong evidence of the maritime activities of this region. The recovery of many woodworking adzes and other artifacts shows that Golabai was a boat-building centre. Significantly, Golabai is the only excavated site in Odisha where boat building has been revealed. This also indicates that Chilika lake was very close to Golabai and it facilitated the maritime trade of people in the area during the ancient period.

Some ancient texts say the southern sector of Chilika was a major harbour for maritime commerce, when Kharavela (c. 209 BCE–after 170 BCE), the King of Kalinga, was known as the "Lord of the Sea".

Ptolemy (150 CE), the Greek geographer, referred to Palur as the port ''Paloura'', located close to the point of departure situated outside of the southern tip of the lake at Kantiagarh, from where ships bound for different parts of Southeast Asia sailed. After 639, the Chinese pilgrims Fa-Hien and Hiuen-Tsang mention a famous port "''Che-li-ta-loChing''" near the shore of the ocean which was a thoroughfare and resting place for seagoing traders and strangers from distant lands. This port was located at 'Chhatragarh' on the banks of Chilika Lake.

A fourth-century legend, often told to explain the birth of Chilika, states that the pirate king, Raktabahhu, planned to attack Puri with a huge fleet of ships. To avoid detection, he stealthily anchored out of sight, off the mouth to the sea. The deception was revealed by the ships' refuse floating to the shore, thus warning the town's people, who escaped with all their possessions. Raktabahu felt betrayed when he found an abandoned town and directed his fury towards the sea
that had betrayed him. The sea parted to let the army march in, then surged back, drowned the army and formed the present lake.

Archeological excavations discovered seventh-century ship anchors and stone memoirs dedicated to battle heroes at a village named Kanas, about north of Chilika on the banks of Nuna river, which flows into the lake. This gives evidence of a historic naval engagement off the coast.

A 10th-century text, the Brahmanda Purana, mentions Chilika Lake as an important centre of trade and commerce, and a shelter for ships sailing to Java, Malaya, Singhala, China and other countries. This suggests that the lake was then deep enough for berthing seagoing ships and had a channel to the sea big enough for loaded trading ships embarking to Southeast Asia. The villagers around Chilika Lake still observe an annual festival called "''Bali Yatra''" (Journey to Bali).

In 1803, the British entered the shores of the lake, reached Puri and occupied Odisha with the help of Fateh Muhammed. Fateh Muhammed, in turn, was rewarded by the British with freehold of the areas of Malud and Parikud, of the present day Garh Krishnaprasad revenue block.

Over the years, poets including Kabibar Radhanath Ray and Pandit Godavarish Mishra, freedom fighters and Saints have extolled historicity of the lake as pertinent to its cultural, spiritual, religious and scenic aspects.

"Gopabandhu Das, a famous Odiya poet, became impatient to see the beauty of the march of colorful sights and sounds of Chilika lagoon while going by train. He asked the speeding train to stop for a moment so that he could enjoy the beauty. It is because of the beauty that arrests him much".

Geology

The lake is of estuarine character in an ephemeral environment. Geological studies indicate that the coastline extended along the western shores of the lake in the Pleistocene era with its northeastern region lying under the sea. That the coastline has moved eastward over the ages is supported by the fact that the nearby Konarak Sun Temple, built originally on the seashore a few hundred years ago, is now about , away from the coast.

The catchment area of Chilika lake has a rock, sand and mud substratum. It contains a wide range of sedimentary particles such as clay, silt, sand, gravel and shell banks but the major part of the catchment area is silt. Around 1.6 million metric tons per year of sediment is deposited in Chilika lake by rivers Daya and several streams.

It is conjectured that a rise in worldwide sea levels over the last 6,000–8,000 years occurred with a pause in the rise of sea level about 7,000 years ago, which could have resulted in the formation of a sandy beach near the coast at the Southern sector. With the rise in the sea level, the sand beach grew gradually, progressed seaward to the northeast and formed the spit of Chilika. A fossil unearthed from the southwestern edge of the spit indicates that the lake was formed about 3,500–4,000 years ago. The abrupt change in the direction of the coast north of the lake, strong winds shifting sand to the shore, longshore drift (littoral drift), the presence or absence of strong river and tidal currents in different areas are the reasons attributed for the growth of the spit.

White bands of coral in the southern sector, at a height of , above the present water level, shows that the area was once marine and that the water was much deeper than present. The chronological development of the outer barrier spit of the lake has been dated by Optically stimulated luminescence studies of minerals. This was done on sixteen samples of the lake bed. The studies indicated doses of between 153 ± 3 m Gy and 2.23 ± 0.07 Gy, corresponding to ages from 40 years at the top of the spit to 300 years at the bottom. The youngest ages are consistent with the age of the overlying vegetation. A clearly defined period of > of barrier construction 40 years ago is identified. Prior to that the deposition rate was relatively constant for 300 years.'"

Geography and topography

Chilika Lake is a shallow bar-built estuary with large areas of mudflats. The western and southern margins of the lake are fringed by the Eastern Ghats hill range.

Several inland rivers, which bring silt into the lake, control the northern end of the lake. A long barrier beach called Rejhansa, formed by northerly currents in the Bay of Bengal, resulted in the formation of this shallow lake and forms its eastern side. As an ephemeral lake, its water surface area varies from in the summer monsoon season to in the winter dry season.

The lake has numerous islands. The larger islands, separated by shallow channels, lie between the barrier and the main body of the lake. A total of channels connect the lake with Bay of Bengal. The six major islands are ''Parikud, Phulbari, Berahpura, Nuapara, Nalbana,'' and ''Tampara''. These islands, together with the ''Peninsula of Malud'', constitute the ''Krishnaprasad Revenue Block'' of Puri District.

The north shore of the lake is part of Khordha District and the western shore is part of Ganjam District. Due to siltation, the width of the barrier has fluctuated and the mouth to the sea has periodically been closed. The location of the mouth has also frequently shifted, generally towards the northeast. The mouth, which was wide in 1780, was only forty years later. The local fishermen, to maintain their livelihood, had to cut open the mouth regularly to gain access to the sea for fishing.

Water depth of the lake varies from in the dry season to in the rainy season. The width of the old channel to the sea, now reported to be about , is known as Magarmukha (Mouth of the Crocodile). The lake is divided into four separate zones namely, the southern, central, northern sectors and the outer channel area. A long outer channel connects the lake with the Bay of Bengal at Arakhuda village. The lake is vaguely pear-shaped and has a maximum length of with a mean width of .

Hydrology

Three hydrological subsystems control the Hydrology of the lake. The land-based system comprises distributaries of the Mahanadi River on the northern side, 52 river channels from the western side and the Bay of Bengal on the eastern side. Two of the three southern branches of the Mahanadi River that trifurcates at Cuttack,
feed the lake. 61% () of the total freshwater inflow into the lake is contributed by these two branches.

The second drainage system which is non–perennial accounts for 39% (). The important rivers of this drainage system are the Kansari, the Kusumi, the Janjira, and the Tarimi rivers. The annual total surface freshwater input to the lake is estimated to including direct precipitation over the lake contributing
All the inland river systems disgorge an annual flow of about of freshwater which is estimated to carry 13 million metric tons of silt into the lake. On the northeast, a channel connects the lake to the Bay of Bengal.

A tropical monsoon climate prevails over the drainage basin area of the lake. The lake experiences South–west and North-east monsoons during June to September and November to December respectively with an average annual rainfall of , with 72 rainy days. The maximum temperature of and minimum temperature of have been recorded. The wind speed varies from /hour with southerly and southwesterly direction due to the influence of the Southwest monsoon and from the north and northeasterly direction during the rest of the months.

Sediment quality

The Chilika Development Authority (CDA) established an organized system of water quality measurements and limnological investigations indicating the following physico–chemical characteristics of the lake waters.
* Lake water is alkaline – pH ranging from 7.1 – 9.6 with total alkalinity matching the salinity. The southern part of the lake near Rambha has recorded the highest alkalinity.
* Bathymetry survey indicates extreme shallow depths in the northern sector, with less than in a large area. The southern sector of the lake has recorded the maximum depth of
* High turbidity due to strong mixing of overlying water with sediments is confirmed by observed transparency values ranging between .
* Salinity levels in the lake show wide temporal and spatial variation due to a complex blend of freshwater discharge, evaporation, wind condition and tidal inflow of seawater. The brackish nature of the lake is depicted by the 0 parts per thousand near the Daya River mouth to hyper-saline level of 42 ppt in the outlet channel during the dry period.
* The dissolved oxygen values were between 3.3–18.9 mg/L.
* Phosphate phosphorus (0–0.4 ppm), nitrate nitrogen (10–60 ppm) and silicates (1–8 ppm) are high in the north and northwest part of the lake where most of the rivers discharge into the lake with large amounts of silt and nutrients.
* The lake is broadly divided into four zones on the basis of salinity values, namely the southern, central, northern and outer channel. Tidal influx of seawater during monsoon is arrested by the strong influx of a large amount of fresh water from the northern and central zones. Brackish water conditions in the southern zone, even during monsoon, prevail due to low water exchange. Salinity in the southern zone decreases during the post-monsoon period and in winter as northern winds facilitate mixing of water with rest of the lake. During the summer, intrusion of salt water from the outer channel into the lake increases since water level of the lake is at its lowest level. A general increase in salinity of the central and northern zones occurs due to wind-induced mixing by the predominantly southern winds and salinity in the southern zone does not rise appreciably.

;Sedimentation:
Adverse tidal exchange occurred due to the littoral drift along the coast line causing flow reduction and shifting of the lake mouth every year. Estimated sediment transport due to this is on the order of 100,000 metric tons. This adverse effect needed ameliorative actions.

Sediment cores were collected from different locations of the lake. The result indicated spatial variation of sedimentation rate in three zones of the lake of /year (Northern Sector), /year (Central Sector) and /year (SouthernSector). The non–uniform sedimentation rate along with the porosity and water content of the sediment cores were also analysed which indicated the lake had different deposition zones, with comparatively higher sedimentation rate in Northern and Central Sector and a slow rate in the Southern Sector.

Conservation – threats and management

In 1971, during Indira Gandhi's tenure as Prime Minister of India, Chilika Lake was designated the first Indian wetland of international importance under the Ramsar Convention due to its rich biodiversity as shown by the facts that:
* Over a million migratory waterfowl and shorebirds winter here.
* Over 400 vertebrate species have been recorded.
* As an estuarine lagoon, it supports a unique assemblage of marine, brackish and freshwater species.
* Several rare and endangered species are found in the region.
* The lake supports fisheries that are the lifeline of the community.
* The lake is of great value in preserving genetic diversity.
* There is an Increase in weeds and aquaculture activities.

Threats

Over the years, the ecosystem of the lake encountered several problems and threats such as:
* Siltation due to littoral drift and sediments from the inland river systems
* Shrinkage of water surface area
* Choking of the inlet channel as well as shifting of the mouth connecting to the sea
* Decrease in salinity and fishery resources
* Proliferation of freshwater invasive species and
* An overall loss of biodiversity with decline in productivity adversely affecting the livelihood of the community that depended on it
* Fights between fishermen and non-fishermen communities about fishing rights in the lake and consequent court cases
The rapid expansion of commercial aquaculture of prawn has contributed significantly to the decline of the lakes fisheries and bird population.

Concerted action was initiated by the Odisha State Government with support from the Government of India to adopt adaptive conservation and management actions.

By 1993, the problems in Chilika were so severe that the lake was put under "The Montreux Record" as the lake was considered to have "undergone, to be undergoing, or to be likely to undergo change in its ecological character brought about by human action". The purpose was to stimulate remedial measures for the lake's conservation, supplemented with adequate monitoring. It was expected that such an action would benefit from the advice from Ramsar Advisory Mission and other identified technical assistance programs.

In summary, siltation from upstream led to shrinkage of the water surface area, decrease of salinity and prolific growth of invasive freshwater aquatic weed infestation, all of which had a serious negative impact on the habitat of wildlife and fishery resources.

Chilika Development Authority (CDA)

In 1992, the Government of Odisha, concerned by the degradation of the lake's ecosystem and cognizant of significant numbers of people who were dependent upon the lake's resources, set up the Chilika Development Authority (CDA). The CDA was set up for restoration and overall development of the lake under the Indian Societies Registration Act as a parastatal body under the administrative jurisdiction of the Forest and Environment Department, with the following charter:
* To protect the Lake ecosystem with all its genetic diversity
* To formulate the management plan for Integrated Resource Management and wise use of the lake's resources by the community depending on it
* To execute multidimensional and multidisciplinary developmental activities either itself or through other agencies
* To collaborate with various national and international institutions for development of the lake

The governing body of the Authority is headed by the Chief Minister of Odisha State and has people's representatives (Members of Parliament and Legislative Assembly), representatives of the fisherfolk communities and secretaries of the key departments, experts and eminent scientists as its members.

In 1998, an executive committee constituted with financial authority, supplemented with financial support from the Tenth and Eleventh Finance Commissions of the Government of India, gave support to the management initiatives taken up by CDA. This facilitated a coordinated approach to plan and implement effective ameliorative management actions.

An Integrated Management Plan was implemented with financial support of Rs 570 million (US$12.7 million) out of "special problem grants" recommended by the Finance Commissions. Hydrobiological monitoring was supported under the Odisha Water Resources Consolidation Project of the World Bank, to the extent of Rs 10 million (US$220,000). A strong support network was created with 7 state government organizations, 33 NGOs, 3 national government ministries, 6 other organizations, 11 international organizations, 13 research institutions and 55 different categories of community groups.

In 2003, a collaboration of Indian and Japanese experts led to a friendly relationship between Chilika lake and Saroma Lake in Japan called ''Sister Wetlands''.

Ameliorative actions

Considering the threats faced by the lake, the National Wetlands, Mangroves and Coral Reefs Committee of the Ministry of Environment & Forests, Government of India, also identified the lake as a priority site for conservation and management. The ameliorative actions were taken by the CDA to restore the ecosystem and to improve the socio-economic conditions of the communities living around the lake and on its islands involved the following.

* Opening the lake mouth
The most effective ameliorative action was the hydrological intervention of opening the new lake mouth and channel to the sea through the barrier beach at Satapura. This improved the spatial and temporal salinity gradients of the lake to maintain the unique characteristics of an estuarine eco-system. This intervention was undertaken after detailed scientific studies, including 3-dimensional mathematical modeling and hydraulics studies on a model prototype, were carried out by the Central Water and Power Research Station, Pune and National Institute of Oceanography, Goa. In September 2000, the desiltation of the channel connecting the lake to the sea and opening of a new mouth to restore the natural flows of water and salinity levels was carried out. These actions resulted in a notable increase in the lake's fish yield and a reduction of freshwater weeds. The new mouth reduced the length of the outflow channel by . Opening of the new mouth provided a favorable increased salinity regime throughout the lake with less fluctuations and improved water clarity.

Other measures included:
* Catchments management in "participatory micro-watershed management in a whole ecosystem approach".
* Protection of bird habitat and of bird species.
* Economic incentives to the local population to stop poaching of birds.
* Measures to improve the socio–economic conditions, such as training programmes to develop eco-tourism.
* Provision of solar streetlight systems to island villages.
* Development of a ferry service for isolated villages.
* Construction of landing facilities for fisherfolk, as well as education and environmental awareness activities.

In 2002, Chilika was taken out of the Montreux Record, in light of the improved conditions of the lake. Chilika lake is the first Ramsar site in Asia to be
removed from the Montreux record.

Awards

* In November 2002, the Ramsar Wetland Conservation Award was presented to the Chilika Development Authority for "outstanding achievements in the field of restoration and wise use of wetlands and effective participation of local communities in these activities".
* The Indira Gandhi Paryavaran Puruskar, constituted by the Ministry of Environment and Forests, Government of India awarded the prestigious Indira Gandhi Paryavaran Award–2002 to the Chilika Development Authority for the outstanding contribution of conservation and restoration of the Chilika lake eco-system.

Flora and fauna

The ecological richness of the lake is of great value in preserving the genetic diversity because of the multiplicity of its habitat, flora and fauna. (Some are pictured in the photo gallery). The Zoological Survey of India (ZSI) surveyed the lake between 1985 and 1988 and identified 800 species of fauna, including many rare, endangered, threatened and vulnerable species, but excluding terrestrial insects.

The rare and threatened animal species identified are green sea turtle ( EN), dugong ( VU), Irrawaddy dolphin ( EN), blackbuck (NT), Spoon billed sandpiper ( CR), Chilika limbless skink (CR) and fishing cat ( VU). 24 mammalian species were reported. 37 species of reptiles and amphibians are also reported.

Flora

Recent surveys revealed an overall 726 species of flowering plants belonging to 496 genera and 120 families. This represents about one –fourth of the vascular plant species of the Odisha state where some 2900 species altogether are found. Fabaceae is the most dominant plant family followed by Poaceae and Cyperaceae. Certain species were found to be characteristic of specific islands.
The flora is predominantly of aquatic and sub-aquatic plants. The species reported are leguminosae, poaceae, and cyperaceae; endemic cassipourea ceylanica; five species of seagrass, and more.
Important species identified are:.
* Leguminosae, Poaceae, and Cyperaceae
* Endemic '' Cassipourea ceylanica''
* Five species of seagrass
* Wild plants of horticultural importance and interesting plant groups such as insectivorous plants, epiphytes, parasites and lithophytes
* Mangrove associates, such as ''Aegiceras corniculatus'', ''Excoecaria agalloch'', ''Salvadora persica'', ''Pongamia pinnata'', ''Colubrina asiatica'', '' Capparis roxburghii'', '' Macrotyloma ciliatum'' and many others.

Fauna

Chilika Lake is the largest wintering ground for migratory birds, on the Indian sub-continent. It is one of the hotspots of biodiversity in the country. Some species listed in the IUCN Red List of threatened animals inhabit the lake for at least part of their life cycle.

White bellied sea eagles, greylag geese, purple moorhen, jacana, flamingos, egrets, grey and purple herons, Indian roller, storks, white ibis, spoonbills, brahminy ducks, shovellers, pintails, and more.

Migratory water fowl arrive here from as far as the Caspian Sea, Baikal Lake and remote parts of Russia, Mongolia, Lakah, Siberia, Iran, Iraq, Afghanistan and from the Himalayas. A census conducted in the winter of 1997-98 recorded about 2 million birds in the lake.

In 2007, nearly 840,000 birds visited the lake, out of which 198,000 were spotted in Nalbana Island. On 5 Jan 2008, a bird census involving 85 wildlife officials counted 900,000 birds of which 450,000 were sighted in Nalabana. Removal of invasive species of freshwater aquatic plants, especially water hyacinth

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