Guwahati: The Subansiri Lower Hydroelectric Project (SLHEP) helped moderate a surge in the Subansiri River’s flow following heavy upstream rainfall. At the same time, an early flood warning system provided downstream communities with nearly six hours to prepare, officials said on Tuesday.
According to a statement issued by the project authorities, the Subansiri River’s discharge began rising sharply shortly after midnight on July 13, increasing from around 7,000 cubic metres per second (cumecs) due to heavy inflows from upstream.
The flood early warning systems installed at Daporijo on the Subansiri River and Tamen on the Kamala River detected the rising water levels and issued alerts nearly six hours before the flood peak.
Following the alerts, district administrations downstream were informed immediately, and warning sirens were sounded around midnight to caution residents living along the riverbanks about the expected rise in water levels.
Officials said the river discharge continued to increase through the morning, reaching a peak inflow of around 13,000 cumecs at 10:45 am on July 13.
As the Subansiri River’s estimated safe carrying capacity is around 7,000 cumecs, the Subansiri Lower Hydroelectric Project used its reservoir to moderate the flood surge. The project reduced the peak inflow to an outflow of approximately 12,000 cumecs at around 11 am, helping delay and lessen the intensity of the flood wave downstream.
The river later showed a receding trend, with discharge falling to around 7,500 cumecs by Monday evening. By 9:30 am on July 14, the river flow had further declined to 5,200 cumecs, according to project authorities.
Officials said the timely operation of the early warning system, coupled with the flood moderation measures at the project, enabled downstream communities to take precautionary measures before the peak flow reached them.
Project authorities also cited local television reports indicating that the advance warnings and controlled release of water helped reduce the impact of the high river discharge on downstream areas.
The Subansiri Lower Hydroelectric Project has been equipped with flood forecasting and early warning systems to improve preparedness and minimise risks for communities living along the downstream stretch of the river during periods of heavy rainfall.