The delicate salinity gradient of the lake disrupted; locals claim Odisha government’s Chilika Development Authority (CDA) not monitoring new mouths regularly
The intense storm surge that had accompanied extremely severe cyclone Fani in early May 2019 had opened four new mouths in the Chilika Lake in Odisha. These were distinct from the main mouth of the lake where it opens into the sea.
While two of the new mouths closed down in April 2022, two others are still open, affecting the biodiversity of the lake and the livelihoods of the people dependent on it.
"Our fish catch has gone down by 30-40 per cent after Cyclone Fani,” Mayadhar Jena, a fisherman and the sarpanch of Mirjapura village, told Down To Earth. He, like many others in his village, has no other means of earning an income other than fishing.
Many of the villagers are now thinking of moving to other states in search of livelihoods. Around 60 men from the village already work in other states, especially in the cement factories of Surat, Gujarat.
In Arakhakuda village, which is closer to the new mouths, the situation is even more dire. “Our fish catch has gone down by 70-80 per cent after Cyclone Fani,” said Litusam Behera, a resident of the village.
“The main mouth of the lake is also closer to our village right now,” he added. The mouth has moved 2 kilometres northwards since Cyclone Fani made landfall between Chilika Lake and Puri.
The main occupation of the village is also fishing and they are now looking for other livelihoods such as labour work or migrating to other states, which is the trend in many villages in the area.
Both Jena and Behera claimed that the Odisha government’s Chilika Development Authority (CDA) has not been monitoring the new mouths regularly or informing them about the possible impacts of the excess sea water ingress into the lake.
“We do field monitoring of the sea mouth of the Chilika Lake every month. In 22 years, the mouth, with a length of 80 metres, that we had opened in 2001 has migrated 7.2 km towards the north. This process is happening pretty quickly due to coastal erosion,” RN Samal, scientific officer of CDA, told DTE.
“In 2008, another mouth opened up to the north of the main mouth, which we also monitor regularly. During each of the major cyclones that have hit Odisha in this period, new mouths have opened up but have also closed down in a matter of a month or so.”
The total area of the mouth needs to be 1,500 square metres for the salinity gradient to be maintained, according to Samal. Currently, the cumulative area of the three mouths is around the same value, he said.
Jena counters this by saying that “there is no way that putting together the areas of the three mouths can be anywhere close to 1,500 square metres. It is much more than that.”
Samal gives a different reason for the fish numbers going down along the mouth region of Chilika lake. “The fish catch has gone down due to overfishing by the local people, especially of juveniles, and has nothing to do with the new mouths,” he said.
Chilika is the largest brackish water lake in Asia with a rich biodiversity created and nurtured by a delicate salinity gradient. This gradient is maintained by the sea water flowing into it through the mouth and freshwater from 52 small rivers and rivulets flowing in from the other side of the lake.
The mouth of the Chilika Lake exhibits longshore sediment transport due to which the sand on the beach and close to the shore move due to a combined action of tides, waves and winds.
This has always made the mouth area of the lake volatile but such a sustained opening of new mouths has never happened before. This could be hampering the fish, prawn and crab numbers and diversity of the lake. Around 95 per cent of these species are dependent on the salinity gradient of the lake for their migration and reproduction behaviour.
In 1981, due to the significance of its biodiversity, the lake had become the first Indian wetland to be listed under the Ramsar Convention. Over the subsequent two decades, freshwater coming into the lake from the rivers increased, disturbing the salinity gradient. This degraded the ecosystem of Chilika and impacted the livelihoods of the local people.
In 1993, due to this degradation, the lake was listed under the Montreux Record as a threatened wetland ecosystem. Between 1975 and 2001, the water level in Chilika had risen by 1-1.5 metres, which was mostly due to freshwater ingress.
To address this, CDA opened up a new mouth towards the south of the old mouth in 2001. This caused the old mouth to close off and restored the salinity gradient. It also rejuvenated the ecosystem’s health and livelihoods of the fisherfolk dependent on it.
A proper study on the impacts of Cyclone Fani on the Chilika lake has still not been carried out, according to Samal.
“If the new mouths do not close down and sea water continues to enter the lake, it could be disastrous for the ecosystem as the biochemistry of Chilika would change,” Pradipta Muduli, scientific officer at Chilika Wetlands Research and Training Centre (WRTC) in Balugaon, which is part of CDA, had told DTE in May 2019.
“For instance, the species with low salinity tolerance like some of the macrophytes and weeds will die, which might affect other fish species dependent on them. This could also impact fish catch”, he had added.
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