Dying Padma, Teesta threaten biodiversity in Bangladesh
The arbitrary withdrawal of water upstream across the border by India is slowly but steadily killing Bangladesh’s two major rivers, the Padma and Teesta, which are considered integral parts of the country, according to river experts and researchers.
India is pushing Bangladesh into a dangerous situation by the arbitrary withdrawal of these two rivers, the negative impacts of which affect land and people down to the sea with the gradual elimination of biodiversity and destruction of river-based livelihoods, they said.
They came up with the observations after being aware of the findings of a recent study that the water flow in the river Padma has decreased by 26 per cent over the past four decades and that the river’s permanent water area has shrunk by 50 per cent during the dry season after the construction of the Farakka Barrage in India.
In March, the Rangpur divisional office of the Department of Fisheries revealed to New Age that about 90 per cent of fish and most of the other aquatic life that once made the waters of the Teesta, Dharla, and Brahmaputra rivers their abode have vanished over the past three decades after their flows were reduced because of interruptions upstream in India.
‘The existence of deltaic Bangladesh relies on an intricate network of rivers,’ said professor Tuhin Wadud, director of Riverine People, a knowledge-based civil society movement to restore and conserve rivers.
He explained that the Padma and Teesta are linked to the Meghna River, which flows into the sea.
‘In other words, the water pressure in the Meghna River is weakening, implying that the sea is advancing towards the inland,’ said Tuhin Wadud.
Water Development Board officials said in March that the water flows the Teesta gets, downstream of the Teesta Barrage at Gajoldoba in West Bengal, are mostly natural as India does not release any water through the barrage during the lean months, turning the river into a stream, broken by long stretches of sandy riverbeds, most of the time.
The WDB officials said that four canals were arbitrarily withdrawing water from the Teesta in West Bengal before the state government recently decided to dig two more canals to serve some 1 lakh farmers in Jalpaiguri and Cooch Behar.
A group of seven researchers from Bangladesh, Australia, and the United Kingdom conducted the study with the support of Rajshahi University and the University Grants Commission of Bangladesh.
The study findings were published in the Netherlands-based journal ‘Biodiversity and Conservation’ in January.
Shams M Galib, an associate professor in the fisheries department at Rajshahi University, coordinated the research team. He said that they had investigated the response of the fish fauna to hydrological, climate, and anthropogenic factors from 1982-2017 in the lower Ganges River, Bangladesh.
He said that the study was conducted on a 70-kilometre area of the Padma from Godagari in Rajshahi to Sarada in Charghat upazila. Fish species were collected at nine points in the area.
After the opening of the Farakka Barrage, the river flow during the dry season has reduced to 2,333 cubic metres per second in 2019. This is compared to 3,685 cubic metres per second in 1974, the report said.
The reason for the lower water flow is that an increased proportion of flow is diverted by the Farakka Barrage to the river Hooghly towards Kolkata.
According to the report, the permanent water area and the depth of the river have also significantly reduced from 140 square kilometres in 1984 to 70 square kilometres in 2019 and from 12.8 metres in 1985 to 11.1 metres in 2019, respectively.
The report showed that the freshwater supply had been reduced by up to 90 per cent. In addition, the average annual rainfall in the Padma basin area has decreased by 19.2 per cent.
In 1981, the annual average rainfall was 5.2 millimetres, while it was recorded at 4.2 millimetres in 2019. The air temperature increased from 25.1°C in 1981 to 26.2°C in 2019.
Due to the reduction in the river’s permanent area, water flow, and depth, nearly one-third of the native fish species available in 1982 disappeared, as the researchers found only 77 fish species in the river during a survey between 2007 and 2017.
In 1982, there were 133 fish species available in the Padma, the study said.
The report shows that about 60 per cent of the fish that have disappeared from the Padma are threatened with extinction in the country.
It was also observed that the Rajshahi City Corporation was the major source of water pollution, as eighteen major drains carrying untreated wastewater from the municipality and adjacent areas entered directly into the river.
To reduce the effects of many stressors on the Ganges downstream of the Farakka Barrage, the research recommended taking immediate action.
River researcher Mahbub Siddiqui told New Age that about eight crore people in the northern and southern regions were badly affected by the Farakka Barrage as Bangladesh was deprived of its guaranteed water share of 65 per cent.
He urged the government to sign the UN Watercourses Convention to get a fair share of river water as the Ganga water-sharing deal between India and Bangladesh expires in 2026.
Bangladesh used to get between 60,000 and 70,000 cusecs of water before India constructed the Farakka barrage over the Ganges in 1975, with 109 gates capable of diverting 40,000 cusecs of water, according to Rivers of Bangladesh, a book penned by M Inamul Haque, former chief engineer of the Bangladesh Water Development Board.
The Ganges water sharing treaty 1996 entitles Bangladesh to only 26,000 cusecs, said the book, adding that the Ganges river flows 130 km after entering Bangladesh in Kushtia before merging with the Jamuna near Goalondo.
The mixed flow of the Ganges and the Jamuna, of which the Teesta is a tributary, is known as the Padma, according to the book.
The Padma flows about 104 km and eventually merges with the Meghna, which flows into the sea, according to the book.
Once a mighty river, the Padma is reduced to a rather weak water body, said Tuhin Wadud, adding that water flows in the Teesta drop so low at times that it cannot be accounted for in a water level estimation.
‘India arbitrarily diverts water from transboundary rivers to meet its increased water demand, which is neither legal nor civilised,’ said Tuhin Wadud.