IIT Madras' dredging methodology helps Odisha's Chilika Lake to triple Irrawaddy Dolphin population

A research project by the Indian Institute of Technology (IIT) Madras has helped Odisha's Chilika lake, Asia's largest brackish water body, in tripling the population of the Irrawaddy dolphins. The searchers conducted geotechnical, hydraulic and satellite imagery studies and developed a dredging methodology with minimum impact on the lake ecosystem.

The process of dredging consists of the excavation (loosening or dislodging) of the material from the bottom, removal of the loosened material to the dredge vessel and ultimately transportation of the material to the placement area.

The intervention by the premier institute also benefitted the over 200,000 fishermen living in 132 villages as it resulted in a seven-fold increase of fish catch and tourists to co-exist with the lake ecosystem with minimal disturbance to the environment, the team claims.

"Chilika Lagoon is over 4,000 years old and spread over the Puri, Khurda and Ganjam districts of Odisha. The highly productive ecosystem of the lake supports the livelihood for fishermen and also acts as drainage for Mahanadi river basin," R Sundaravadivelu, Professor at Department of Ocean Engineering, IIT Madras said.

"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," he added.

"The geotechnical, hydraulic and satellite imagery studies showed the spit of Chilika is constantly changing. The sand bar has been widening, and the position of the mouth constantly shifting, moving generally towards the northeast. The mouth was described as being about 1.5 km wide in 1780 and had decreased to half within forty years in 1820."

"It also showed the Chilika lake mouth located originally near Sipakuda in 1800 has gradually shifted in the last 200 years towards the northern side to Arkhakuda," he said.

The IIT Madras team 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, the flood inundation and freshwater weeds are reduced. The hydrological intervention restored the lake ecosystem and ameliorated the biodiversity. The fish production increased 7-fold and the population of highly threatened Irrawaddy dolphin increased," Sundaravadivelu said.

"The enhancement of fishery resources and the increase of population of Irrawaddy dolphin promoted ecotourism which immensely benefitted the local fishers," he added.

Restored at a cost of Rs 10 crore by opening the mouth and other related works in six months’, the lake is now off the threatened list (Montreux record).

The Chilika Lake Authority has developed an Ecosystem Health Report Card and periodical monitoring of salinity, fish and dolphin, freshwater weeds, birds and other biological parameters are being carried out.