4 min readGuwahatiNov 6, 2021 07:39 PM IST
First published on: Nov 6, 2021 at 06:44 PM IST
Even after a week, the waters of Kameng river, a major tributary of Brahmaputra river in Arunachal Pradesh’s East Kameng district, continued to remain black, muddy and unsuitable for use, authorities said.
“Satellite imagery has indicated some sort of a landslide/avalanche in the upper reaches of the river as the possible cause. While we still do not have the complete picture yet, it is fair enough to say that the riverine ecology is in a distressed situation and will need time to rejuvenate,” said Praivimal Abhishek Polumatla, DC, East Kameng district.
While experts agree that there was a likely avalanche which led to high turbidity, they are still trying to determine where it happened and what precipitated it | Express photo
The river changing colour was first reported on October 29, when locals found a large number of dead fish floating in the waters, which had turned black and muddy, near Seppa town.
The state’s public health engineering department ran tests and found that the water was reporting a high level of turbidity (suspended particulates in a liquid) leading to the change in colour. According to the department’s water analysis report, the turbidity level is in the range of 1,290 and 1,380 Nephelometric Turbidity Unit (NTU) — much higher than the permissible limit of 5 NTU. On the other hand, the level of dissolved oxygen has dropped to 2 mg/litre, lower than the acceptable level of 8-10 mg/litre, said Polumatla.
He said that this depletion in oxygen levels had led to the death of thousands of fish initially and now, several have swum away to other tributaries.
The Kameng river (called Jia Bhorelli in Assam) is a lifeline for many and has its source in a glacial lake near the Nyegi Kangsang, one of the highest mountains in Arunachal Pradesh.
While experts agree that there was a likely avalanche which led to high turbidity, they are still trying to determine where it happened and what precipitated it. On Friday, the district administration carried out an aerial survey of the river and found that there was intense erosion along the Warriyang Bung — a tributary of the river upstream in the Khenewa Circle — which had led to deposition of mud, debris, boulders and trees that the river carried downstream. However, they were unable to determine where the landslide had occurred.
“We did an aerial survey as far as we could go but the weather was not conducive as there was heavy cloud coverage. We will wait for a few days, if the weather clears, we may get a clearer picture,” said Dani Sulu, Secretary, State Disaster Management, Arunachal Pradesh.
The state government is in touch with multiple agencies, including the State Remote Sensing Application Centre in Itanagar, North Eastern Space Applications Centre in Shillong, Indian Space Research Organisation and Central Water Commission as well as independent researchers, to monitor the issue.
A release from the state disaster management department Monday said there were many glaciers upstream of Warriyang Bung and that they had “moved”. “However, it remains to be seen whether these glacial movements are normal or abnormal,” it added.
Chintan Sheth, an independent researcher who is assisting the state government with technical inputs, said he was exploring multiple triggers that may have led to the landslides and debris flow. “Some possibilities include temperature, rainfall data as well as ground displacement data. The National Centre for Seismology detected an earthquake close to the incident site on October 13. However, it is too early to implicate any trigger at the moment,” he said.
As of Saturday, the district administration restrictions under Section 144 of the Criminal Procedure Code (CrPC) — prohibiting people from venturing into the river and fishing, selling or consuming its fish — continues to be in place. The administration has also collected fish samples for food safety testing, and asked the villagers to remain vigilant in case of an outbreak of any disease.
“We are trying to gather as much evidence (before it is lost) to understand what happened to the riverine ecosystem and trying to see if there is anything we could do to accelerate the rejuvenation process,” said Polumatla.
The river changing colour was first reported on October 29, when locals found a large number of dead fish floating in the waters, which had turned black and muddy, near Seppa town | Express photo 
While experts agree that there was a likely avalanche which led to high turbidity, they are still trying to determine where it happened and what precipitated it | Express photo
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