:: Welcome To Chilika Lagoon

Opening of a new mouth opposite to village Sipakuda :

As per the findings of the CWPRS, Pune, it was concluded that the salinity flux and tidal flux into the lagoon would not improve unless the location of the lagoon mouth get closer to the lagoon proper. Based on their three dimensional numerical model studies, they recommended that an experimental mouth with 100M width and 2.5M below the lowest lagoon water level must be dredged, so that the salinity flux into the lagoon would improve by 40% and the tidal flux would improve by 45%. This would rejuvenate the Lagoon ecosystem and the desired level of salinity i.e., 15 ppt during summer in northern sector can be achieved. Accordingly the opening to the sea was also accomplished opposite to the village Sipakuda on 23^rd September 2000. This was carried out as per the technical guidance of the CWPRS, Pune as well as Ocean Engineering Centre, IITM, Chennai. NIO Goa carried out the monitoring of the lagoon. After the desiltation, the monitoring of the lagoon is carried out to assess the impact of the desiltation by National Institute of Oceanography, Goa to assess the impact of the opening of the mouth on the lagoon eco system. The close monitoring of the lagoon is also carried out by CDA at an interval of thirty days.

IRS 1D LISS III IMAGE OF CHILIKA LAGOON
DATE-23^RD SEPTEMBER 2000

Phase-II of desiltation :

The major rivers like Daya, Bhargavi and Luna the distributaries of Mahanadi river system drain in to the lagoon in the northern sector. These river systems drain 4385 million cumec of fresh water into the lagoon. The bed sediments like clay, silt and pebbles, (the higher gravity particles) brought by the above rivers are deposited in the river mouth. Based on the model studies the Central Water and Power Research Station, Pune have further recommended that the area adjoining to Daya, Bhargabi outfall point is remaining fresh-water up to Barakudi, and is also totally infested with fresh water weed, which is also obstructing the free flow of water and sediment. Therefore, they have recommended extension of the dredge channel from Muggermukh to the river confluence point of the Daya and Bhargavi over a length of 22.6 kms. The extension work is now in progress and expected to be completed by August, 2003. It is predicted that the channel will have the following positive impacts :

1. The channel will facilitate free flow of fresh water from the rivers draining to the Chilika and will be helpful in maintaining the mouth. Due to efficient disposal of flood water, the water logging problem along the north-western periphery of the lagoon will reduce.

2. The channel will help in flushing-out of the sediment.

3. Due to the propagation of the salinity the fresh-water invasive species growing in the northern sector will reduce, and the water spread area of more than hundred square kilometres will become free from fresh waterweed. It will also facilitate the migration of Hilsa fish .

IMPACT OF THE DESILTATION AND NEW MOUTH ON CHILIKA ECOSYSTEM

The opening of the artificial mouth is considered as an historic and successful intervention in the history of the restoration of the eco system of the wetlands in India, which is evident from the following positive impacts, which are noticed after the desiltation of the outer channel as well as the opening of the new mouth.

Salinity :

The northern sector of the lagoon was remaining freshwater almost through out the year, but after the opening of the mouth, the salinity level of the northern sector improved appreciably to, 26.2, 21.2 & 31.2 ppt, at station no. 17,18 & 19 respectively, during the month of May’2001, against the average salinity level of 0.5 to 2.5 ppt recorded during the same period in past one decade.

Salinity Level (Pre-Monsoon-May-2000)before opening of N.M.

Auto-recruitment of fish, prawn & crab :

The gradual reduction in the salinity from the lagoon mouth to the lagoon interior after the opening of the mouth is providing the desirable sense of direction for the eurohaline forms to enter into the lagoon from the sea. This is facilitating the auto-recruitment of the fish, prawn and crab juvenile in to the lagoon.

Fish, prawn & crab landing :

As against the annual average fish landing of 1600 metric tons, recorded during the past six years, the fish landing during the year 2000-2001 improved to 4889.21 MTs. and the seven months landing after the opening of the new mouth i.e., from October 2000 to March 2001 alone was 3718.44 metric tons. During the year 2001-2002, the landing is recorded to be 11988.88 metric tones, which is a record production, and an all time high in the history of Chilika. During the year 2002-2003 inspite of a severe drought year, the total landing of fish and prawn was 10743.98 MT. The total prawn landing was 2,478.82 MT and Crab landing was recorded to be 149.81 MT which are considered as all time high in the record.

1. Annual Fish and Shrimp landing from Chilika Lake

The fish, prawn & crab landing (1993-94 to 2002-03) from Chilika lagoon :

Crab landing :

The crab landing was recorded to be 79 metric tons during 1985-86 but it decreased sharply to 3 metric tons during the year 1994-95. After the opening of the mouth i.e. during the year 2000-01 due to the abundant recruitment of the crab juvenile into the lagoon the crab landing touched 93.54 MTs, 111.07 MT in 2001-2002 and 149.81 MT during the year 2002-2003, which is the all time high for past one decade.

2. Annual Crab landing from Chilika Lake :

Re-appearance of threatened species :

After opening of the mouth, 6 species of fish ( Hilsa (Tenualosa) ilisha, Megalops cyprinoides, Elops machnata, Chanos chanos, Rhinomugil corsula, Rhabdosargus berda), and 2 species of prawn (Penaeus indicus & Metpenaeus monoceros) which had disappeared from the lagoon, reappeared. The total landing of this species during June and July 2000 was recorded to be 438 MT including 200 MT of Penaeus indicus which is higher than the last 6 years total annual landing of prawn from capture source.

Migration of fish :

After opening of the new mouth, the distance between the lagoon and the opening to the sea is decreased by 18 km (the distance between old mouth and new mouth) this is facilitating the migration of the catadramous and anadramous species in to the lagoon. The average salinity level of northern sector during summer improved to 15 ppt against the recorded salinity level of 2-5 ppt during past few decades.

Good practices :

The increase in the fishery resources facilitated the conducive atmosphere for the community to adopt self initiated good practices, like regulation of the mesh size, stopping of the juvenile poaching etc. It is a real experience to see that the community with the public address system on the boat is spreading the message for use of the net with big mesh size to spare the juvenile in side the lagoon. It is also paving the way for an effective channel of communication through consultation with the community who depend on the fishery resources of the lagoon and to adopt co-management strategies. The CDA and the local community are now able to understand the problem and able to formulate joint strategy through sharing and exchange of information. As an IEC activity at a regular interval, the information on wise use and good practices are communicated through the newsletter and pamphlets in local language by CDA.

Reduction of fresh water weed :

Due to fall in salinity and the increased load of sediment as well as the fertilizer residue from the crop fields surrounding the lagoon, the spread of the fresh water invasive species was going up. The weed spread area was 20 sq.km in 1972, which proliferated to 684.70 sq.km in May 2000, with a weed free area of only 351.51 sq.km. After the opening of the new mouth, the weed free area was computed to be 508.51 sq.km (May 2001 CDA) through the image-processing unit. So there was a reduction of 157.05-sq.km of the weed spread area. The monitoring of the aquatic weed is carried out by the use of image processing tool

this is being done under the direct supervision of the CE, CDA. One of the most positive finding is that the invasive species like water hyacinth is reducing which are replaced by the reed (Phragmites karka).

Formation of seagrass meadows :

Sea grasses are the sole marine representatives of the angiosperms. One of the most productive ecosystems on earth is the sea grass meadow. These are encountered in estuaries, lagoons, and shallow open shelves off the seacoast, which serve as nursery ground for a large number of fish and invertebrate species, and provide the critical habitat for dugongs and turtles. They also play an important role in the food web of inshore coastal areas. Prior to the opening of the new mouth of the lagoon, the most common sea grass species recorded was Halophila ovalis (paddle weed), which is more tolerant of low salinities and low light condition, than other sea grass species. The distribution of the above species was also poor and extremely patchy in the lagoon. Small beds of Ruppia maritima were observed to be common in the shallow waters of southern and central sectors in association with Halophila sp. mostly along the shoreline. After opening of the mouth the species, diversity of the sea grass is being observed to be improving as three new species of sea grasses. Halophila is also recorded for the first time in the deep waters from the creeks of the Krushna Prasad island with prolific growth during post monsoon months forming extensive meadows. The opening of the new mouth provided stable salinity regime with less fluctuations, improved water clarity, especially during post monsoon and summer months, which are perhaps the reason for the luxuriant growth and formation of sea grass meadows.

Expansion of Irrawaddy dolphin distribution :

Irrawady dolphin (Orcaella brevirostris) is considered as a flagship species of Chilika. Only two lagoon populations of Irrawady dolphins are known in the world; in Chilika lagoon, Orissa, India and Songkhla lagoon, Thailand (Beasley, 2001). Records of distribution are relatively few, although there are some areas of local abundance (Stacey and Arnold 1999). Before opening of the mouth most of the dolphins used to be sighted only along the inlet channel and in a limited portion of the central sector of the lagoon. After the opening of the mouth the Irrawady dolphins were observed to be well distributed in the central and the southern sector of the lagoon. This can be attributed due to the improvement in the water quality, food abundance and decrease of the area covered by weed after opening of the new mouth.

Distribution of Dolphins

Improvement of depth of the channel :

The flushing of the sediment into the sea is now conspicuous and the depth of the channel from Satapada to the new mouth is improving as the silt and clay from the outer channel is observed to be gradually, being flushed out through the new mouth. Due to scouring, the depth of the channel is recorded to have increased by 30-45 cm at different cross sections. The water level variation during the tidal cycle is also now conspicuous and at Satapada it is now 30cms.

Solution to the water logging problems of the Northern Sector and flood mitigation :

Due to efficient disposal of flood water during monsoon, the peripheral villages as well as the island villages were not affected by flood in 2001. The substantial improvement in the efflux also indicates the possibility of decrease in the water level of the lagoon during the monsoon period. The inadequate efflux through the old mouth was assigned as a reason for water logging in the paddy fields of the peripheral villages of Chilika in Kanas and Brahmagiri Community Development Blocks areas, leading to crop loss over more than 50,000 hectares of Khariff paddy crop.