In a unique initiative, researchers from the Indian Institute of Technology Madras undertook a major project at the famous Chilika Lake in Odisha, the largest brackish water body of Asia and the first Ramsar site of India, to help in tripling the population of the Irrawaddy dolphins.
The intervention of IIT Madras also benefitted the over 2,00,000 fishermen living in 132 villages as it resulted in a seven-fold increase of fish catch. It also enabled tourists to co-exist with the lake ecosystem with minimal disturbance to the environment.
The fish production increased 7-fold and the population of highly threatened Irrawaddy dolphin increased. The enhancement of fishery resources and the increase of population of Irrawaddy dolphin promoted ecotourism which immensely benefitted the local fishers.
Chilika Lagoon is over 4,000 years old and spread over the Puri, Khurda and Ganjam districts of Odisha.
In 1981, Chilika Lake was the first Indian wetland designated under the Ramsar Convention on Wetlands of International Importance, an international treaty for the conservation of wetlands.
The highly productive ecosystem of the lake supports the livelihood for fishermen and also acts as a drainage for the Mahanadi river basin. The lake was in a degraded condition and included in the threatened list by Ramsar Convention in 1993. This warranted urgent action for restoration of the lake.
The geotechnical, hydraulic and satellite imagery studies showed the spit of Chilika is constantly changing.
The sand bar is widening, and the position of the mouth constantly shifting moving generally towards the northeast.
The mouth was about 1.5 km wide in 1780 and had decreased to half within forty years in 1820. The Chilika lake mouth, located originally near Sipakuda in 1800, has gradually shifted in the last 200 years towards the northern side to Arakhakuda in the state.
The sedimentation in the South and erosion in the North due to littoral drift is the major cause of continuous shift of the mouth towards the North.
The outer inlet channel of 18 km length was formed between Sipakuda village and Arakhakuda. The tidal exchange through this channel was not sufficient to maintain the quality of brackish water and overall brackish ecosystem of in the lake.
Highlighting the outcomes of this project, Prof R Sundaravadivelu, Institute Chair Professor, Department of Ocean Engineering, IIT Madras, who spearheaded the project, said, “The Chilika Lake was restored with a cost of Rs 10 crores by opening the mouth and other related works in six months’ time which has resulted in fish catch worth Rs 100 crore and revenue of Rs. 35 crore due to tourism every year.”
The Sipakuda mouth, that opened in March, 2000, has significantly improved the ecosystem. The tide levels at Satapada before the opening of the mouth was 10 cm, while this improved to 60 cm, which is the indication of more tidal inflow and stabilising the brackish water nature in the Chilika.
But as the mouth consistently migrating towards the North, another mouth at Gabakund opened naturally. In the process of migration, the Sipakuda mouth merged with Gabakund mouth in 2012 and the width was about 2700 m at the time of merging. Studies conducted indicate the need for further interventions inside the lake like the desiltation.
According to a press statement, IIT Madras developed the dredging methodology identifying the location of dredging along with disposal and selection of suitable dredger with minimum impact on the ecosystem.
Based on the outcome of this successful hydrological intervention by IIT Madras undertaken under the auspices of the Chilika Development Authority (CDA), the flood inundation and freshwater weeds are reduced. The hydrological intervention restored the lake ecosystem and ameliorated the biodiversity.