On 29 September 1948, a large group of farmers had gathered on the banks of the Halda river. Their mission: to cut an oxbow bend of the river to save their cropland from flooding.
In the following hours, the farmers would cut the oxbow bend of the River Halda to straighten its flow but at a great cost. Clash with the police, who were there to stop the farmers from destroying the river, would leave scores dead. What they had not realised then was that their action that day would have far reaching consequences for one of the most unique natural breeding grounds in the world.
Around 80 years ago, an 8-kilometre stretch of the tidal River Halda with an oxbow bend was flowing through Purba Madarsha village in Chattogram's Hathazari. When it rained heavily, river water could not drain fast because of the bend, submerging vast areas of cropland on both riverbanks.
Villagers also had to travel an additional 8km to cross the river although the distance was only half a kilometre as the crow flies.
That is when they decided to cut the Barighona bend to straighten the river. But the local zamindar Ramakrishna Mahajan opposed it, as did the government, backed with scientific data.
As the locals were bent on having their way, the authorities imposed Section 144, a law prohibiting assembly of more than five persons, to tackle the situation. Flouting the order, locals started cutting the bend and in the ensuing melee the police shot dead at least 38 villagers – the official number of deaths was 10.
Such human interventions imperiling the Halda has been continuing for a long period – local villagers have changed the flow of the Halda by destroying at least 11 oxbow bends of the river between 1905 and 2002.
The Halda now flows in a much straighter way. The river's length has decreased by 25.25km to 97.75km from 123km.
Human destruction of river flow hurt fish habitats
Thus human pressure has hurt the river's ecology forever with the ultimate result of fish egg production falling steeply in the only natural carp breeding ground of the country.
According to the Department of Fisheries and the Chattogram University Halda River Research Laboratory, the number of eggs collected from Halda in 1945 was over 1.36 lakh kg, which dropped to 47,000kg in 2001, 21,000kg in 2012 and only 8,000kg in 2021.
However, good weather conditions still cause occasional blips in egg production. For instance, during the years when there was a lot of rainfall, favourable temperature and a minimum influx of saltwater in the waterbody, about 33,000kg of eggs were hauled in 2008, 23,000kg in 2018 and 25,536kg in 2020.
Experts say Halda is a unique river in the world because of its oxbow bends. These bends are the main habitats for carp fishes, where brood fishes lay eggs. People's destructive cutting of the bends have impacted marine life. Fish habitats have vanished, leading to damage to the world's best natural breeding ground for carps.
A study conducted by the Bangladesh Fisheries Research Institute identified the destruction of 11 oxbow bends over the last 100 years as one of the 10 human interventions to the destruction of the Halda's biodiversity. Dr Md Manzoorul Kibria, professor of zoology at Chattogram University, was in charge of the Fish Biology Analysis chapter of the research.
Manzoorul told The Business Standard, "Every year between the Bangla months of Chaitra and Ashar, hill water flows into the river after thunderstorms during a full moon and a new moon. And, river water in the oxbow bends becomes muddy and foamy. Mother carps lay eggs during this time if physicochemical factors are created there and temperature stays favourable at 25-28 degrees Celsius."
Salinity is also a killer
Salinity in the Halda has been increasing because of temperature and sea-level rises due to climate change.
This year, the spawning was very poor in the absence of natural phenomena like downpours, hilly torrents and thunderstorms. On top of that, the eggs were spoiled because of increased salinity and high temperature.
On 27 May, salinity in the river increased 77 times than normal after tidal water rushed into the Halda with an unusual height under the impact of cyclone Yaas. Salinity was 36.9 ppt (parts per thousand), while it is only 0.5 ppt during normal times, according to the Halda Resource Laboratory of Chattogram University.
According to Chattogram Wasa, the maximum salinity found in Halda was 400 ppm (parts per million) in 2004, which gradually increased to 4,000 ppm in May 2021. But, during cyclones, the amount of salinity increases abnormally, such as during cyclone Sidr in 2007 when salinity rose to 11,550 ppm.
Dr Manzoorul said, "The presence of Patalnagini snakes in the Halda is evidence of increased salinity in the river. This species is frequently being found by fishermen in the river. Besides, several species of marine shrimps, including Laila, are now present in the Halda."
Three upstream dams are holding one-third of the river water. On the other hand, Chattogram Wasa pumps 180 million litres of water from the river daily. Halda Parallel Project pumps 250 million litres of water during the irrigation season. But, the Kaptai Hydropower Station does not supply enough water. As a result, saline water easily enters the waterbody from the River Karnaphuli, he said.
Abdur Rahman Rana, director of the Center for People and the Environment, a research institute on climate change, said, "Temperature is rising because of climate change, which is above 30 degrees Celsius during spawning time. Irregular rain and a rise in temperature are responsible for the destruction of the spawning environment in the Halda."
Dams and irrigation deplete water
Salda is a hilly village in Batnatali union of Manikchhari upazila of Khagrachhari. The River Halda is named after the village as it originates from a hilly flow there. It enters the district at Fatikchhari upazila at its north-eastern corner. Dhurung is the main tributary of Halda. The two streams would rapidly drain the upstream water causing a crisis in that region.
To mitigate water crisis of local farmers and bring surrounding barren agricultural land under cultivation, the Ministry of Local Government Rural Development and Cooperatives constructed a rubber dam 4.50 metres high and 12 millimetres wide on the River Halda at Bhujpur in Fatikchhari in the fiscal 2010-11. But this dam has now become another cause of the river's destruction.
A year later, another rubber dam was built on the Harualchhari canal 10km off Bhujpur, which is directly connected to the river. At the same time, a concrete dam was placed at the fast-flowing tributary Dhurung.
Because of these dams, at least six-kilometre upstream of the Halda remains dry for four months every year. Besides, the normal flow of water has been disrupted with the installation of 18 sluice gates in 19 connecting canals of the river, which hold about 35% of its river water.
Factory and residential wastes from Oxygen to Kulgaon areas in the Chattogram city go into the river through the Khandakiya canal.
Researchers say the environment and biodiversity of the river is now on the verge of collapse.
Dr Manzoorul said, "Rubber dam in Bhujpur holds 20% of Halda river water. Besides, about 15% more water is unable to flow downstream through Harwalchhari and Dhurung canals. Due to the dam, the presence of benthos, the staple food of carp fishes like Rui and Kalbaush, has almost vanished from a 20km area of the river. As a result, the presence of Kalbaush is only 3%, Rui 6%, Mrigel 20%, and Catla 70% in the river."
Ainun Nishat, professor emeritus of Brac University, said, "Fishes swim upstream when there is a thunderstorm after the Bangla month of Chaitra. Later, when the weather is favourable, the female lays eggs and the male fish releases sperm. The fertilisation happens with water turbulation. But fish habitats have been destroyed with the sluice gates."
Local resident Mostafizur Rahman Chowdhury said, "Local tea gardens are benefiting due to the rubber dam in Bhujpur. But the river has seriously been affected by the dam and local farmers have suffered a lot because of it. When the rubber dam is inflated for more than three metres, the flow of water downstream is completely stopped."
Will Halda survive?
The uncoordinated development projects of various government agencies such as rubber dams, dumping of sandbags and blocks, and sluice gates have brought this river to its death throes.
Besides, various industries along the river and the 100-megawatt power plant in Hathazari are also contributing to the river's pollution.
Prof Ainun Nishat said, "I think the Halda should be given a few years. Already salinity has increased anew. Nature has the power of rejuvenating. I think five years from now, the fish will go more upstream to lay eggs, and gradually they will try to adjust to the water."
He also suggested removing upstream rubber dams and releasing more water from Kaptai Lake to reduce salinity in the Halda.
In recent years, the government has taken different initiatives to save the river.
On 22 December last year, the government declared the Halda River as Bangabandhu Fisheries Heritage and imposed 12 restrictions.
The restrictions include: no fish or aquatic animals can be caught or hunted from the Halda river. The oxbow bends of the river cannot be straightened under any circumstances. No new rubber and concrete dams can be built on the river and its connecting canals. Water cannot be extracted by setting up new water treatment plants and irrigation projects without the permission of the Bangabandhu Fisheries Heritage Supervision Committee. Industries and other establishments cannot discharge any garbage into the river and fishes cannot be caught during the breeding season (February to July) in 17 canals connected to it.
Earlier, in 2015, an office order of the Ministry of Fisheries and Livestock decided to restore the Garduara bend of the Halda and keep the other bends intact. However, no initiative has been taken yet.
The district fisheries office implemented a project called the Halda River Natural Fish Breeding Restoration Project at a cost of Tk14 crore from 2006 to 2014.
It is meant to support the fishermen during the no-fishing period in the Halda. Under the project, in 2010, about 2,000 fishermen were given a loan of Tk10,000 per person for one and a half years. In 2011, they were given 40kg of rice for two months. The support continued until 2015. From 2013 to 2015, an average of 60kg of rice was given to each family every year.
In 2007, a 20km stretch of the River Halda from Sattarghat to Madunaghat had been declared a sanctuary.
The government has stopped tobacco cultivation on more than 100 acres of land on both banks of the river in Manikchari and helped the farmers with aid.
Dr Md Manzoorul Kibria said, "All types of fishing have been banned in Halda since 2010. Earlier, there was a balanced presence of all the fishes in the river. We need to ensure community-based fishing management to protect fishes and ensure balance."