Cyclone Fani opens four new mouths in Chilika lake, increases salinity, wipes out fish

As Mayadhar Jena, 47, stepped into Chilika Lake to anchor his boat, he was visibly shocked. A new large mouth of the lake had opened up. There were already two mouths connecting the lake to the Bay of Bengal. “That’s why our fish catch has gone down,” he says. Jena is the sarpanch of the twin villages of Mirjapur-Parbatipur, located close to the mouths of the lake. Due to waves of intense energy lashed by the extreme severe cyclone, Fani, on May 3, four new mouths have opened up. Now there are six mouths.

Chilika is the largest brackish water lake in Asia. The salt content or salinity, comes from seawater that enters the lagoon from a small inlet that runs parallel to the sea and opens up at a place known as the mouth. Freshwater comes from 52 small and large rivers that drain into the lake, largely from Daya and Bhargavi rivers. The lake’s salinity varies—from 0 in the northern sector, where there is complete freshwater, to 33 in the mouth, which is complete saltwater.

This delicate salinity gradient between different parts of the lake supports a wide variety of ecosystems. “Any disturbance to this salinity gradient either by incursion of more freshwater, polluted water or seawater can be detrimental to the health and survival of myriad species of plants and animals that Chilika supports,” says Ajit Pattnaik, vice president of non-profit Wetlands International South Asia and former chief executive of the Chilika Development Authority (CDA).

For its wealth of biodiversity, Chilika was recognised as the first site in India under the Ramsar Convention on Wetlands of International Importance in 1981. But in 1993, it was included in the Montreux Record as a threatened ecosystem whose character was changing due to heavy influx of freshwater from the rivers upstream. Between 1975 and 2001, the water level in Chilika had risen by 1 metre to 1.5 metres, which was mostly due to freshwater ingress.

To counter this, CDA opened up a new mouth to the sea in 2001, successfully restoring its character. “We studied salinity levels, conducted hydrodynamics modelling and analysed how similar sites were restored in Japan to locate and characterise the inlets from the sea,” explains Pattnaik. The dredging of the new inlet and mouth increased fish production and gave a new lease of life to almost 0.2 million fisherfolk who are dependent on Chilika for survival. For example, between 1950s and 1980s, there was no water hyacinth in Chilika, but after the new inlet was opened the plant flourished, creating a positive cascading effect for aquatic species that live around hyacinths.

BUT SEVERE CYCLONES like Fani can easily foil such success stories. More mouths on the Chilika can affect the delicate balance of the ecosystem. For example, migration and re-production behaviour of around 95 per cent of finned and shell fish species depends on the salinity gradient of the lake. Species like mullets and sea bass get their sense of direction for migration from the salinity gradient. When there is a sudden decrease or increase in salt levels, fish numbers go down.

Salinity also depends upon seasons. During monsoon, when the lake’s freshwater content increases, fish migration towards more saline waters begins, and once this freshwater recedes and salinity gets restored, they return to the lake.

THE FOUR NEW mouths are towards the north of the original mouth which is around 2 km from Mirjapur. The first and second new mouths are around 2 to 4 km from the original mouth. The third and fourth mouths are towards the north. “These mouths will not close down and salinity even in the interiors of the lake will increase,” says Jena.

But officials counter Jena’s statement. “The mouths will close down in a matter of months due to the long range sediment transport along the coast from the southern part of the lake towards the north,” says Susanta Nanda, the chief executive of CDA. Such south to north sediment transport of almost 1 million cubic metre of materials along the littoral zone takes place all along the Indian coastline which gives the river deltas their unique shape. Littoral zone is the area closest to the shore where sunlight penetrates to the sediments at the bottom of the seafloor and allows aquatic plants to grow. The sediment transport usually plugs the mouths. Therefore, CDA had to create a regulatory lead channel of 1.2 km to infuse flow pressure from the lake side to counter the plugging of the mouth. In the past 19 years, the mouth has migrated 2 km up north because of these dynamic coastal processes.

Pattnaik says sediment transfer is crucial, but in the region where the new mouths are located, it is tedious making them thin. This has happened because of the accumulation of sediments near the original mouth which is blocking their transfer further north. This might make the process of closing down of the mouths slower than it should normally take. But Pattnaik believes that there is enough sediment transport to close down the mouths in one month as it happened during cyclone Phailin in 2013, when a new small mouth opened and was then closed.

“At present, the salinity levels have increased but they are comparable to the levels observed during the same period last year,” says Pradipta Muduli, scientific officer at Chilika Wetlands Research and Training Centre (WRTC) in Balugaon, which is part of CDA. Scientists at WRTC monitor salinity, water quality, oceanography, microbiology and species diversity at 33 locations every month. Research is also being conducted at the centre on some specific parameters like heavy metal contamination in fish and petroleum hydrocarbon levels of lake water where there are regular patrols of motor boats.

CYCLONE PHAILIN HAD a different impact on Chilika. Unlike Fani, which was characterised by its extraordinary wind speed, Phailin carried a lot of rain with it. Muduli and his team had carried out hydro-logical and biochemical analyses after Phailin to study its impact. The study found that a lot of freshwater came into the lake and decreased its salinity level. This killed most of the seaweed in the area but everything returned to normal within a few months. But Fani’s case is different. “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 bio-chemistry of Chilika would change,” says Muduli. 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, says Muduli.

Fani, which made landfall close to Puri, also destroyed the tree cover along coastal Odisha and even in the interiors. This includes both natural forests and plantations like coconut, areca nut, cashew nut and casuarina. Along the stretch from Puri to Konark in Balukhand Wildlife Sanctuary, home to the Olive Ridley turtles and blackbucks, tree cover has been decimated. This has pushed many animals out of forest area towards human habitations. The district forest officer has now issued a notification asking people not to get into conflict with animals. Though officials have not made an exact estimate yet, there are reports that Fani damaged and uprooted up to eight million trees in the sanctuary.

“Plantation techniques have to be changed in an era of global warming where severe storms and heavy flooding will become more common,” says Dinabandhu Sahoo, director of Institute of Bioresources and Sustainable Development in Imphal. Massive loss of tree cover also increases the chances of excessive heating of the land and disturbance in moisture and wind regulation could lead to heat traps and heat waves. “Heat waves have become more common after the super cyclone in 1999,” observes Pattnaik.

Fani was the worst tropical storm to hit the Odisha coast in the last 20 years, killing 69 people and destroying infrastructure worth R12,000 crores, according to preliminary estimates. The Odisha government, with the help of regular forecasts from the India Meteorological Department, accomplished a great job of evacuating 1.2 million people along the coast. This timely action saved many lives, but the more difficult task is to resurrect the livelihood of the affected people.

Take for instance the plight of Tanumali, 58, a rice farmer in Thengipada village, located on the road from Bhubaneswar to Puri. He lost his house in the 1999 super cyclone and rebuilt it after great toil. He lost it again in the floods last year. He had saved some money so he could rebuilt his house. And now Fani has destroyed his house yet again. His family of eight has been living with no food and electricity since May 3. Nobody from the government has come to enquire about their condition. “It will take at least 50 years for the people of Puri district to recover from the impact of Fani,” says Jagannath Bhoi, a coconut farmer in Sarangajodi village while walking through his farm where 90 per cent of the coconut trees have been plundered.

Another blow is the destruction of boats of fishing communities. Of the 236 registered boats in Mirjapur, 160 have been damaged. It will cost up to R2 lakh for each boat to be repaired. “I don’t know how we can come out of this without help,” says Kumud Behara, 32, a fisherfolk from Mirjapur.

Fani’s long-term impact on the environment and livelihoods of the people needs to be studied, especially as the Bay of Bengal is most likely to experience more severe cyclones in the future due to global warming and slowing local wind speeds.

But research on the long-term impacts of extreme weather events on environment and livelihoods is hard to find. So officials have no idea whether to rebuild or to rehabilitate. “Long-term studies need to be conducted to know what is really happening and whether this is because of climate change,” says R K Dey, additional principal conservator of forests, Union ministry of environment, forest and climate change, eastern regional office, Bhubaneswar. “Everyone starts doing research on one part of the problem, but then it gets lost as there is no one to take a larger perspective. Nobody is serious about doing research on climate change,” he concludes.

(This article was first published in Down To Earth's print edition dated June 16-30, 2019)

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