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Ecological Characteristics and Issues

As a background to defining current resource management problems within
Chilika Lagoon, this section of the report describes the Lagoon ecosystem and the current status of the aquatic resources. Relevant features of the ecosystem directly supporting, or contributing to fisheries and  aquaculture production, are highlighted.
 

This includes a consideration of general features of lagoon ecology,
followed by a systematic review of information pertaining to lower trophic levels and commercial aquatic resources. This is followed by; an evaluation of several different forms of aquaculture of present or potential significance within Chilika Lake.
 

General Lagoon Ecology

High nutrient concentrations are often present in Lagoons as a result of both riverine nutrient inputs and effective nutrient recycling between the sediments and the water column. Lagoons are, therefore, often highly productive aquatic environments. A comparison of productivity land biomass estimates for lagoons around the world (Tables 4.1 and 4.2 in Barnes, 1980) clearly indicates that Lagoons are characterized by exceptionally high productivity and biomass, compared to other aquatic ecosystems. The following features provide lagoons with their distinctive characteristics.
 

·    the high degree of shelter from tidal and current action;

·    the relatively stable salinity gradients;

·    the soft mud and/or sand substrates;

·    the well-mixed nature of the water column through wind action;

·    extreme shallowness;

·    organic richness;

·    rapidity with which they change (over geological time scales);
 

 in climates with seasonal rainfall, and where major inputs of freshwater exist a pronounced seasonal variation in salinity and/or water level.In comparison with estuaries, contributions of phytoplankton and submerged macrophytes in lagoons are more important in production processes. Most of the production is consumed within the system, and there is less export of nutrients and organic material due to the closed nature of lagoons and of the unimportance of tidal fluxes. Carbon sources include phytoplankton, ;benthic and epiphytic algae and detritus derived from macrophytes. The latter detrital source is especially important as a source of carbon. The pond weed, Potamogeton ppectinatus decays very rapidly within the lagoon environment. Studies by Howard-Williams and Davies (1979, cited by Barnes 1980) suggest that under environmental conditions of 15-260 C temperature and 5-11 ppt salinity, most nutrient release from Potamogeton occurred during its first week of decay, and decay processes very largely complete within 128 days. Within lagoons, detrital enrichment via bacterial heterotrophs is the dominant trophic pathway supplying energy to biological consumers.

Most of the consumers are thought to acquire detritus, benthic algae and epiphytes in an indiscriminate fashion via deposit feed and/or browsing. Among vertebrates within lagoons (both birds and fish) most species are opportunistic omnivores or carnivores.
 

In summary, lagoons are extremely productive environments due laragely to high nutrient inputs from surrounding land drainages, as well as efficient nutrient re-cycling. This high productivity supports lagoon fisheries for both fish and shell fish. Lagoons are ephemeral environments (on geological time scales) evolving rapidly into other types of semi-aquatic, habitats (marshes, swamps). Simultaneous with this succession is a gradual shift from high salinity conditions to freshwater. Human activities within lagoon watersheds often serve to increase the succession rate of lagoons towards their ultimate terrestrial end-state. Virtually all of these general processes appear to be currently operating within Chilika Lake.
 

o   the high degree of shelter from tidal and current action;

o   the relatively stable salinity gradients;

o   the soft mud and/or sand substrates;

o   the well-mixed nature of the water column through wind action;

o   extreme shallowness;

o   organic richness;

o   rapidity with which they change (over geological time scales);

o   in climates with seasonal rainfall, and where major inputs of freshwater exist a pronounced seasonal variation in salinity and/or water level.
 

In comparison with estuaries, contributions of phytoplankton and submerged macrophytes in lagoons are more important in production processes. Most of the production is consumed within the system, and there is less export of nutrients and organic material due to the closed nature of lagoons and of the unimportance of tidal fluxes. Carbon sources include phytoplankton, benthic and epiphytic algae and detritus derived from macrophytes. The latter detrital source is especially important as a source of carbon. The pond weed, Potamogeton ppectinatus decays very rapidly within the lagoon environment. Studies by Howard-Williams and Davies (1979, cited by Barnes 1980) suggest that under environmental conditions of 15-260 C temperature and 5-11 ppt salinity, most nutrient release from Potamogeton occurred during its first week of decay, and decay processes very largely complete within 128 days. Within lagoons, detrital enrichment via bacterial heterotrophs is the dominant trophic pathway supplying energy to biological consumers.
 

Most of the consumers are thought to acquire detritus, benthic algae and epiphytes in an indiscriminate fashion via deposit feed and/or browsing. Among vertebrates within lagoons (both birds and fish) most species are opportunistic omnivores or carnivores.
 

In summary, lagoons are extremely productive environments due laragely to high nutrient inputs from surrounding land drainages, as well as efficient nutrient re-cycling. This high productivity supports lagoon fisheries for both fish and shell fish. Lagoons are ephemeral environments (on geological time scales) evolving rapidly into other types of semi-aquatic, habitats (marshes, swamps). Simultaneous with this succession is a gradual shift from high salinity conditions to freshwater. Human activities within lagoon watersheds often serve to increase the succession rate of lagoons towards their ultimate terrestrial end-state. Virtually all of these general processes appear to be currently operating within Chilika Lake.
 

Bird Ecology

The bird ecology of Chilika Lake is summarized in a recent report commissioned by the Feasibility and Design Mission, undertaken by Associates Project Bihang (Dev 1991), an NGO based in Bhubaneswar, actively involved in ecological research on birds in Chilika Lake. The following statements on bird ecology are abstracted from this source.
 

The bird fauna of Chilika Lake is diverse, and includes 151 species belonging to 26 families (Table 2.3). The avifauna is predominated by 22 species of ducks and geese, 52 species of plovers and sandpipers belonging to 8 families, 14 species of gulls and terns, 13 species of eagles and 11 species of herons and egrets. Due in part to the importance of Chilika Lake for migratory species of Arctic and Central Asian waterfowl (e.g. flamingoes), the site is internationally important as one of two Indian wetland conservation sites designated under the Ramsar convention. Out of the 151 species, 92 species are considered by Dev (1992) as long-distance migrants, and the rest are considered resident or local migrants. Chilika is particularly important to migratory waterfowl as a wintering habitat, during which time both bird numbers, as well as a bird diversity, show seasonal peaks (Figure 2.9). Specific information concerning bird feeding requirements, habitat selection, protection and research requirements are summarized in Dev (1992).

 

Socio-economic Characteristics and Issues

Community Dependence on the Lake

 

Chilika Lake has 132 fishing villages with a total population of more than ten million not including the surrounding area which has about 273 villages. About 30% (33,300) of the fishing village population are active fishermen, although many others depend indirectly on the fisheries. The specific methods of fishing are a reflection of the particular caste characteristics of the community.
 

The complex mix of resources in and around the Lake, water, fish, land, forests and fauna, have an interrelated effect on community life. It is difficult to precisely arrive at a geographical area, and consequently, at the communities which should be included in a resource management plan for the Lake. More specifically, farm land, mostly paddy fields, is spread all around the Lake and irrigation water with pesticides like Thimet and Ecalux and fertilizers drain straight into the Lake. The forest area is spread over the entire western side up to 30 km distance, denudation of which for fuel and timber purposes add to the sedimentation of the Lake. Thus many communities, with very different socio-economic backgrounds, are one way or another linked to resources in and around the Lake.

Three distinct communities can be identified as having crucial linkages to the Lake and its resource management:

a.  the fishermen (traditional and non-traditional),

b. the farmers who live around the lake, and

c.  those who depend on the forest resources in the Lake catchment area for both their livelihood and to meet their fuel/timber requirements.

 

Traditional Fishermen : Their caste and status

The traditional fishermen are Harijans - the "Untouchables" and hence they occupy the lowest social position in the society. In addition, their poverty continues to reinforce this lower social position as, in the changing Indian village scenario, social status and economic power go hand in hand.

 

There are seven sub-castes of fishermen

Keuta (also known as Kaibarta or Khatia) - constitute 68% of the fishing population; generally fish only with nets.

Kandara - constitute 14% of the fishing population; operate traps like Dhaudi and Thattas for catching prawns and crabs;

Tiar - (also known as Ghadi) constitute 7%; generally use bamboo traps called bejas and menjhas;

Nolia - constitute 7%; Telegu fishermen who catch mainly marine fish and fish near the Lake mouth; use drag nets and cast nets;

Niary (Niaries) - constitute 2.3%; operate nets but do not use traps;

Gokha - constitute less than 1%; operate drag nets.
 

There is significant status differentiation between the subcastes primarily related to economic status. But between Khatia and Tiara there are only marginal differentiations. While Khatias claim that they occupy the highest position, others challenge this. Kondras are the lowest of the sub-castes.
 

The fishermen still live separately from the caste-Hindus. Some ten to fifteen years ago, the fishermen were not even permitted to enter the caste-Hindu villages and untouchability prevailed. Things have since changed significantly; the fishermen take baths in the village open pond where caste-Hindus also take baths and celebrate certain village temple festivals together. However, in a few places, some discriminations still prevail. For example, drinking water wells are separate, separate vessels are kept for them in the hotels, they have to carry the bridge for marriage, play traditional music, etc. Social awareness, education and economic development are crucial aspect which can enhance social status in the society.

 

Forests

There is a large forest area both on the coastal side and around the lake which quote successfully is being covered by casuarina (near the sea shore), eucalyptus and cashew under both a SIDA-supported and the government's own social forestry programme. But the tribals and the local communities entirely depend upon the forest to meet their own fuel requirements and they also cut and sell it in the local market. Also, the tribals supply bamboo to the fishermen to make fishing tools and leaves to make leaf-plates. Some fisherwomen, while returning after selling the fish in the villages around, cut and bring home fuelwood. In some fishing communities, women spend five to seven hours almost everyday to bring leaves to meet their fuel requirement. Fuelwood is in short supply and hence it provides employment to a large number of families. The caste-Hindus cut and bring fuelwood in cart and cycle loads whereas the Harijans and the tribals bring in head-loads. The number of families live exclusively on the forest. It was stated by the people that they have to go deeper and deeper into the forest as forests are getting cleared and denuded. It contributes to floods and sedimentation in the Lake. Hence, the forest is significantly linked to the Lake and the fishing community in many ways. The linkage between poverty and environment is quite obvious, for they said that they had to depend upon the forest for their livelihood and that given an alternate income source they would change their occupation. These relationships need to be further understood.
 

Thus, there is a need to intensify the forest and soil conservation programme and provide alternative income generation and energy sources for those who depend upon the forest for both livelihood as well as to meet the local energy requirement. The proper energy planning is essential.


Agricultural Land

The area around the Lake, not covered by human settlements and forest, is under intense farming - mainly cashew in dry land and paddy cultivation in wetland. Water from these farms, carrying fertilizer and pesticide residues, drain straight into the Lake. Moreover, the farming community, which is the most powerful economically, socially and politically, has taken over by force the lands around the Lake which have become dry due to the shrinkage of the Lake, and is bringing them under agriculture or aquaculture. These farmers have also taken to fishing, money lending (to fishermen) and fish marketing. This has led, on the one hand, to conflict between the traditional and the neo-fishing communities and, on the other hand, to the dependence of the fishing community on the non-fishing communities making the latter more powerful. This enables them to control the pricing of fish in their favour which keeps the fishermen poorer.
 

It was mentioned that the farmers in the western area took to fishing because of failure of crops due to flooding in the last ten consecutive years. The fishermen who had generated some surplus capital invested in farmland because of less catch of fish. The farmers were anxious to get back to farming if flooding could be controlled and adequate measures are made to ensure irrigation but the fishermen would like to continue with farming. The more fishing and prawn culture has become commercialized, the more farmers have entered the fish business.
 

Thus, farming practices, the socio-economic profile of the farming communities and the dynamics of the relationship between the traditional fishing and the "neo" fishing communities are important areas of inquiry. Indepth socio-economic studies need to be undertaken.
 

The data regarding use of fertilizer and pesticide reflect that within a decade the use of fertilizer for agriculture purpose has become nearly double. Out of the NPK, the amount of nitrogen far exceeds the amount of potassium and prosperous, accounting for more than 80% of total fertilizer used. The run off into the lagoon during monsoon has undoubtedly enriching the bottom detritus leading to faster growth of aquatic vegetation.
 

Birds

 

The migratory birds during winter attract tourist, "birdwatchers". Poaching of the birds is encountered in few pockets. Here again, there is a linkage between poverty and nature. Hence, poaching needs to be studied from a socio-economic perspective and alternative employment potentials need to be identified for the poachers. An aspect which needs to be noted is that the fishermen are bird-lovers. The birds not only help them identify the location of fish but also bird abundance is associated with greater fish production and hence fish catch.

Chilika Lake is famous for the vast numbers of migratory waterfowl that flock there every winter, and the lake is reputed to support the largest concentration of migratory waterfowl in India (Scott, 1987; Ram et al., 1994). In the 1960s, the lake annually supported millions of ducks and thousands of geese in the winter months, butover the past two decades populations have declined considerably, although the numbers are still impressive (Scott, 1987). As with many reports about Chilika Lake, various sources provide quite different views, and species lits and total numbers vary considerably. Scott (1987) reports "over 150 species" and "no comprehensive counts have been made". Dean and Saltink (1991) report of 500,000 – 700,000 migratory birds annually, consisting of over 150 species. Bandyopadhyay and Gopal (1991) record about 150 species of which 97 are migrants, and that in 1989-90, when conditions were particularly suitable, about wo million migratory birds visited Chilika Lake. Ram et al. (1994) report of over 160 species, of which "atleast 97 species are migratory", but do not give total numbers, other than quoting Bahdyopadhyay and Gopal (1991). The Asian Waterfowl Census (Parennou & Mundkur, 1994) reports that in 1992, Chilika was comprehensively counted, and that there were indications that the area "supports up to a million waterbirds", although they recommend count augmented by aerial surveys. In all, they report a total of 103 waterbird species at Chilika.
 

The first migrants, usually Golden Plover Pluvialis fulva and Green Sandpiper Tringa ochropus, arrive in September when Nalaban Island is still submerged – they converge on the periphery of the Lake, near Balugaon. Ducks usually arrive by late September or early October and Nalaban usually surfaces by January (pers. Comm.Acharya, 1997). During the present survey, Nalaban had just barely surfaced, and consisted mainly of one large mudflat, with some ‘ridges’ with several decimeters elevation, and a few semi-artificial hillocks. The latter were observed to be mainly used by birds of prey and ibis.
 

Due to disturbances in areas in and around Chilika Lake, about 75% of all waterfowl (pers. Comm. Acharya, 1997) tend to converge on Nalaban Island, which has been gazetted as a bird sanctuary and forms a safe haven. This high concentration of birds can be observed during the winter, as much of the 1,500 hectare island. However, as there are no hides, observers could be seen from afar, and most birds species tended to keep at least 200-400 meters away. Flamingo’s were even more wary, staying at least 600-800 meters away from the observer.
 

In any case, it is obvious that Chilika Lake is of great importance to migratory birds, and in addition to supporting large to very large numbers of waterfowl, it also provides a refuge for certain rare and endangered species, such as the Spoon-billed Sandpiper Eurynorphynchus pygmaeus, Asian Dowitcher Limnodromus semipalmatus and Goliath Heron Ardea goliath. Birds of prey seen at Chilika include the Brahminy kite Haliastur indus, the Pariah Kite Milvus migrans, Crested Honey-buzzard Pernis ptilorhynchus, Black-shouldered Kite Elanus caerulens, Sparrow-hawk Accipiter nisus, White-bellied Sea-eagle Haliaeetus leucogaster, White-backed Volture Gyps bengalensis, Pale Harrier Circus macrourus, Pied Harrier Circus melanoleucos and Marsh Harrier Circus aeroginosus, but also rare species such as Palla’s Fish-eagle Haliaeetus leucoryphus and Osprey Pandion haliaetus.
 

Dolphins

 

The Irrawaddy Dolphin (Orcaella brevirostris), is a somewhat elusive species, found in various large rivers, bays and estuaries in South and Southeast Asia. It’s IUCN Red Data Book status (Groombridge, 1993) is ‘undetermined’, but suspected to be Rare, Vulnerable or Endangered and it is listed in CITES Appendix II. Irrawaddy Dolophins are found in Chilika Lake, but it’s status is somewhat uncertain as reports are conflicting. Ram et al (1994) report that this species was once abundant in the Lagoon but today it is endangered, although it can occasionally be seen near the Lake mouth. Others, however, are more optimistic. Dean and Saaltink (1991), for instance, report that 60-70 dolphin can regularly be seen in the channel between Satapada and the Bay of Bengal, while Patnaik (Principal Chief Conservator for Wildlife, MoEF Orissa State, pers. Comm.1997) report of a total population of 157 dolphins. The MoEF Research Scholar based at Chilika for 21/2 years, Ms Smita Acharya, reports that about 50-60 dolphins occur, mainly in the southern sector, which is the deepest part of the Lake (Acharya, pers. Comm., 1997). Fishermen at the Lake inlet confirmed that dolphins used to occur at the Lake mouth, but now were found only in the deepest part of the Lake.

Irrawaddy Dolphin in Chilika Lake are likely to be affected by the various recent changes in Chilika Lake, and their long-term survival appears threatened. The three most important factors affecting the species are: the apparent drastic decline in fish numbers (endangering their food supply, siltation, and decline in water quality. Most abundantly the Dolphins are spotted along the outer channel upto the Satapada. The detail ecology of the animal is not yet studied.
 

Physical Characteristics and Issues

Geomorphic Features and Coastal Processes

 

Many of the current management issues within Chilika relate to its status as a lagoon ecosystem. A general overview of lagoon ecology is provided by Barnes (1980) who compared a large number of lagoon ecosystems around the world. Lagoons are highly dynamic, ephemeral aquatic systems, which once formed, persist for time periods of between hundreds and thousands

of years. The lagoon lifespan is believed to be positively correlated with size. Thus large lagoons like Chilika may persist for considerably longer than 1000 years. Barnes (1980) makes the point that lagoon biology can only be understood within the framework of lagoon formation, evolution, and subsequent decline.
 

Lagoons are usually formed when a portion of the sea is enclosed by offshore or lognshore barriers. Sand is a common barrier material which can form into a spit which extends across inlets or bays of the sea, thereby forming a lagoon. Lagoons are shallow systems with maximum depths rarely in excell of 10m. Because of their shallowness, lagoons are ralatively easily converted into swamps, marshes and ultimately land by plant colonisation and encroachment (except in more saline lagoons). Many of these successional trends are currently operating within Chilika Lake.
 

Chilika Lake is a classical tidal lagoon, created by a beach barrier berm that developed by the accretion of coastal sediments following the stabilization of sea levels some 3,000-4,000 years ago. It differs from some lagoons because of the large influx of fresh water, particularly during the mornsoon season, which gives the lagoon a brackish characteristics.
 

Geomorphic features are shown on Figure 2.1. The lagoon owes its existence to three principle geomorphic features :

  • The weathered hills that anchor the southwestern limit of the lagoon;

  • The delta of the Mahanadi Riever to the northeast : and,
     The barrier berm.

The weathered (denudational) hills are comprised of hard, metamorphic rocks, that trend from the coast toward the northesast. Prior to the emergence of the contemporary shoreline, it is likely that the seaward extremity of these hills jutted into the bay of Bengal forming a promontory and a large embayment on the leeside of the prevailing southwest monsoons. The rock promontory was subsequently encaptured by sediments, leaving a cliff facing the sea in an area presently referred to as the Palur Hills.
 

Although monsoon winds also blow from the northeast, wind and wave records, together with the alignment of coastal features, indicated the prevailing direction of winds, waves and sediment transport along the coast is from south to north. Based on an analysis of ship-based wave observations, the National Institute of Oceanography (NIO), estimated the net coastal sediment transport is about 1.5 x 10 6 m 3 per year, with the majority of this movement taking place in the months of March to October. A reversal in the direction of transport occurs in the months of November to February (Chandramohan et al, 1989).
 

This northerly sediment transport, which ranks as high as any location in the world, delivered coastal sediments from the south, past the Palur Hills, pushing them into the bay which was later to become the existing lagoon. It is likely the coastal sediments would have initially been transported in a more northerly direction than at present, following the alignment of the rocky hills into the bay. The sediments formed barrier islands under the combined interactive processes of wave refraction,, wind (aeolian) transport, and emergence of the rocky hills. An sediments accreted, and the barrier formations increased in size, the alignment of the barrier features swung more to the northeast, seeking to be parallel to the incident southerly waves.
 

Concurrently, the delta of the Mahanadi River prograded into the Bay of Bengal distributing sediments to the coast via a classical "birds-foot" delta, comprised of multiple distributary channels that nature uses to discharge excessive sediments more efficiently to deep water. Two distributary channels, the Daya and Bhargavi, presently discharge into Chilika Lake.
 

Some of the sediments delivered to the coast by the Mahanadi River would have been transported southward, eventually intermingling with the sediments from the south, participating in the coastal processes, and forming barrier berms and coastal dunes.
 

Fine sediments from the Mahanadi and other rivers may have laid down a layer of silt and clay over which the existing fine to medium sized sands have formed as the barrier spit. Vankatarathnam (1970) makes reference to observing an exposed clay base north of the inlet following beach erosion associated with the southeast monsoon season.
 

Sediments delivered to the lake thorought the Daya and Bhargavi Rivers, after the coastal barrier was developed, infilled about 400 km 2 of the lake leaving between 900 to 1,200 km2 of water surface area at present. Thw water surface area at a particular time depends upon the prevailing water level. Landsat imagery indicates the mouth of the Daya River was about 30 km north of its present position following stabilization of sea levels (ORSAC pers, comm.).
 

Attempts have been made to calculate the loss of water area since the turn of the century. However, this data may be questionable because of the sensitivity of the water area to the water level, and also, as pointed out by Dean and Saaltink (1991), area has been lost to prawn culture operations.

Documentation reviewed, estimated the present rate of siltation in Chilika Lake is 735,000m 3 annually, based on some underfined empirical formulae. There are 42 point sources of sediment loading, 5 of which are larger rivers or streams, The extent of flocculation occurring in the system is not known, whereby clay material aggregates into largerr, more settleable, particles upon contact with saline water. Data on the density of settled solids in the lake bottom was not seen in documents reviewed.

The barrier berm, or spit, associated with Chilika Lake is about 60 km long with an average width of 150 m. The southern portion is generally wider and higher than the northern section where the inlet is presently located .
 

Backshore dunes are well developed along the southern half of the spit reaching heights of 9 to 15 m above the beach in two or three parallel series. Along the northern half there is generally just a single dune, which is less developed toward the outlet.

The beach along the foreshore of the spit is comprised of fine to medium sized sand, 0.25 to 0.5 mm diameter. The beach slope is variable depending upon activity, tending to be steeper , at a slope of about IV (vertical): 6H (horizonatal), during the period of June to October, and somewhat flatter, IV: 8H to IV:12H, during November to February. The offshore slope, below low tide, is IV:50H, or flatter.

Although not described in any documentation reviewed, the coastal dynamics will be greatly affected by major cyclones in the area. Large waves, coupled with a rise in the sea level sometimes exceeding 2 m, result in substantial erosion of the beach profiles and overtopping of the spit at one or more locations. Shifts in the location of the inlet would be associated with major storms that breach the spit.
 

The inlet to a lagoon is a product of interaction between waves, currents and sediments. O'Brien (1971) was the first to point that dynamic equilibrium develops at inlets with the cross-sectional area of an inlet being related to the tidal prism, or volume of water exchanged on a tidal cycle. The tidal prism is approximately the product of the surface area of the lagoon times the tide level fluctuation. The tidal prism, and the cross-sectional area of the inlet, decrease with a reduction in lagoon surface area. The tidal fluctuation in Chilika Lagoon is about 0.2 to 2.4 m. Chilika Lagoon also receives the benefit of the Mahanadi River flows in Keeping the tidal inlet open. The lagoon level increases by up to 2 m, by one report, during the monsoon season.
 

Usually, the but not always, the location of an inlet migrates in the direction of the shore transport of littoral sediments. Incident waves generate longshore currents which convey sedimants. The sediments lengthen the spit and encroach on the inlet channels. Sediments driven into the channel are either carried inshore to form a bar, or channel shallows or are swept offshore to a bar which acts as a sediment transport link between the downcoast and upcoast sides of the inlet.

As the inlet migrates the channel connected to the inlet lengthens. This is the case for Chilika Lake where the inlet is connected to the lake through a 25 km long channel. Quite ofter the inlet migrates to a point where flow resistance in the channel is too great and hydraulic forces act to open a new inlet with a shorter connecting channel, such that the process of migration, and subsequent breaching, commence again. Alternatively, multiple breaks can occur in the spit during a storm event, which will be closed leaving a single inlet during more quiescent periods.
 

The location of the inlet to Chilika Lagoon exhibits the effect of the prevailing northerly littoral sediment transport, and a large bar is located offshore on the inlet mouth. Historical records show the inlet has been located in the same general area, within about 10 km, since at least 1914. Estimates of the location of the inlet relative to the village of Arhhakuda are as follows :

1914 - 6 km NE
1965 - 8 km NE
1986 - 41/2 km NE
1991 - 51/2 km NE

The historical records indicate multiple inlets have opened, on occasion, and siltaion had temporarily reduced the inlet cross-section.

Although not substantiated by historical records, the bathymeetry seaward of the spit opposite Satapada, some 20 km south of the present inlet, would indicate the inlet to the lake was located at this location for many years. The 5 and 10 m depth contours show a concave outward fan, typical of a subaqueous point source discharge of sediments, attached to a submarine ridge extending north from the fan.

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