No migratory birds visited Sankhya Sagar this winter; connecting lakes Jadhav Sagar and Madhav Sagar also covered in green layer
Sankhya Sagar has virtually disappeared under the water hyacinths, blocking sunlight and reducing oxygen levels in the lake. Photo: Shuchita Jha / DTE An artificial lake in Madhya Pradesh’s Shivpuri district has virtually disappeared under a thick layer of an invasive aquatic plant, threatening the biodiversity of the water body. The Sankhya Sagar was declared a Ramsar site in July 2022.
The lake spreads across 248 hectares (612.82 acres) with a catchment of 37,522 ha and helps maintain the ecological balance of the Madhav National Park. As a Ramsar site, it is a wetland site designated internationally important by the United Nations Educational, Scientific and Cultural Organization.
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More than six months since the declaration of the lake as a Ramsar site, it is now covered in water hyacinth (Pontederia crassipes), an invasive species native to South Africa. The plant has naturalised itself in many other parts of the world.
While the plant has some uses too, when it covers the entire surface of a water body, it becomes a threat to aquatic biodiversity.
Macrophytes like water hyacinth can’t be outrightly placed in a harmful or useful category, said Ritesh Kumar, director of non-profit Wetlands International, South Asia. “Water hyacinth acts as a water purifier by removing heavy metals from water when present in small quantities.”
However, the plant is a prolific spreader and when it covers the entire surface of a water body, it does not allow sunlight to penetrate the water and also starts depleting oxygen. “This leads to death of aquatic animals and plants, which in turn decompose and further reduce oxygen levels,” Kumar added.
Sankhya Sagar supports significant populations of 19 indigenous fish species, which spawn and breed in its habitat, according to the website for Ramsar wetlands. The water body has a mix of riverine and palustrine (marsh) habitat fish populations, making them critical to maintaining the overall biodiversity of the region.
The fish species, in turn, support the population of piscivorous (fish-eating) birds. Waterfowls are also present here in large numbers. The lake is home to 73 species of birds and welcomes migratory birds during winter.
The lake is also home to marsh crocodiles. Marsh crocodile aka ‘Mugger’ (Crocodylus palustris) is a Schedule I reptilian species protected under the Indian Wild Life (Protection) Act, 1972. The reptiles were introduced in Jadhav Sagar in 1987 by the Madras Crocodile Bank.
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The water hyacinth has covered the lake in a green layer and is leading to the death of native species by depleting oxygen from the water, Uttam Sharma, chief conservator of forest for Madhav National Park, told media personnel.
“Aquatic life and fish are dying due to the water hyacinth, which the crocodiles prey on. Now the reptiles have to search for food outside the water body on the banks of the lake,” he said.
The northern side of the water body is a hilly area and several minor drains join it. The Maniyar river connects the Sankhya Sagar to another lake, Jadhav Sagar, which passes through the national park. A few major feeder drains from Jadhav Sagar join it on the eastern side.
The lake’s western side is downstream and has a dam line — a barrier to control water levels. The water flows through the spillway towards another waterbody, the Madhav Sagar lake. Both Jadhav Sagar and Madhav Sagar are also covered in water hyacinths.
The State Wetland Authority sent a proposal last year to the MP government for notifying both these lakes in Shivpuri under Wetland Rules 2017. After the notification, both these water bodies could apply to become Ramsar sites as well.
“The fact remains that even if we spend Rs 20 lakh and clean Sankhya Sagar, water hyacinth from the connecting water bodies will pollute the lake again. All these water bodies need to be cleaned to prevent the invasive plant from spreading,” added Sharma.
The presence of water hyacinth indicates that there are high nitrogen levels in the water, said Kumar. “It is a symptom of an underlying problem and how the water nutrients behave. It also indicates a lack of effective competing factors to prevent its growth.”
There was a noticeable lack of migratory birds at the lake this winter, thanks to the invasive plant. “Migratory birds otherwise fly to Sakhya Sagar, were not spotted throughout winters this year,” Abhay Jain, a lawyer working on environment issues in Shivpuri, told Down To Earth.
Collector and District Magistrate for Shivpuri Akshay Kumar Singh told DTE in a telephonic conversation that he has spoken to the local municipal corporation and the Chief Minister’s office to get the invasive plant cleared from the local streams and ponds of the city.
However, Sankhya Sagar falls under the forest department and can only be cleaned with the efforts of the director of Madhav National Park.
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Chattri Trust, headed by Rajya Sabha member Jyotiraditya Scindia, manages the Jadhav Sagar Lake. “The cleaning of the lake began a week ago and hopefully will be done in a month if the weather conditions are favourable,” Ashok Kumar Mohite, officer for the trust, told DTE.
“The weather is still cold, so the labourers are unwilling to work. Once the weather gets better, we will call them to clear out the lake. The lake was last cleaned in 1998 and once earlier in 1986. It is a laborious task and will take time,” said Mohite.
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