Algae lends Subernarekha a bright green hue near Mango in Jamshedpur on Tuesday. Picture by Bhola Prasad
Subernarekha, the lifeline of Singhbhum, is under threat. Again.
This time it is not killer hyacinths, but algal blooming — technically known as eutrophication — that is sapping the river of its dissolved oxygen (DO).
A bright green carpet, running 10km between Kapali Ghat (near Domuhani) and Sankosai after Mango Bridge, is what the river looks like now. Environmentalists dubbed the situation alarming and said depleting DO level would gradually snuff out aquatic life.
K.K. Sharma, a green crusader and head of zoology at Jamshedpur Co-operative College, said Subernarekha was once a treasure trove of freshwater fish like eel, rohu and katla.
“Today, algae are multiplying fast on the water surface. The bloom blocks sunlight and air from penetrating water, thereby snapping the river’s oxygen supply. We believe that the current DO level in Subernarekha is around 4ppm (parts per million). If this level drops, fish will die,” Sharma said.
Concerned over the situation, Yugantar Bharati — an NGO championing the cause of environment — collected water samples from 10 places between Domuhani and Mango Bridge to check the level of dissolved oxygen and other parameters like concentration of phosphates, nitrates and heavy metal like lead, turbidity and biochemical oxygen demand.
“We have sent the samples to laboratories in Ranchi and Calcutta. We expect reports in the next two weeks,” said a functionary of the NGO.
Sharma explained that algae thrived in nutrient-rich water. “Phosphates and nitrates are their favourite food source,” he said.
Director of Institute of Environmental Management and Studies N.K. Nag added that stagnation of water was responsible for such algal blooming. “It converts aerobic water into anaerobic water and makes it unfit for use.”
According to Nag, the blanket of algae must be cleaned as early as possible or else the situation will aggravate by summer. “The very existence of the river will be at stake if the growth of algae goes unchecked,” he warned.
Unconfirmed reports said dead fish were seen floating in the river in Laxmi Nagar near Sankosai last week.
In 2011, water hyacinths — jal kumbi in local parlance — had mushroomed on the river surface. The unbridled growth choked aquatic life and turned the river into a breeding haven for mosquitoes.
Sources said regular discharge of domestic, industrial and agricultural wastes into the river were arresting its flow, which is the root of the problem. Environment experts suggested that water from Chandil reservoir and the check dam at Mango should be released into Subernarekha at regular intervals to prevent stagnation.
Regional officer of Jharkhand State Pollution Control Board R.N. Chaudhury promised to look into the matter.
“Last year, we carried out tests and found the level of dissolved oxygen in the river was alright. We are aware of the algal blooming and will carry out a fresh survey to determine the level of dissolved oxygen for further action,” he said.
What should be done to save the river?