Clarification about release of excess water from Ranganadi Hydroelectric Plant in Arunachal Pradesh

Ranganadi Hydroelectric Plant is a run-off-the river plant with a very little storage. Upto a certain inflow due to rainfall in the upper reaches of the Ranganadi Plant, the reservoir can absorb the water. However, whenever there is very heavy rainfall in the upper reaches, the excess water beyond the capacity of the storage capacity is passed through the gates. The water coming through the gate is only due to heavy rainfall which cannot be retained and there is no contribution of the Ranganadi plant in this.

On the contrary, the Plant reduces flood quantum of the river by diverting 160 cumecs of water to adjacent Pare basin. Even in the absence of the Ranganadi plant, the same amount of water if not more would have flown in the river and reaches the downstream plains of Assam.

The Ranganadi River has many tributaries; many of them are in the downstream of the dam. So all the water flows through the river and reaches Assam. There is an incorrect perception that the flood in Lakhimpur is because of release of water from Ranganadi dam. Flood in Lakhimpur is not a new phenomenon and is happening much before the construction of this plant. It is purely due to heavy rainfall in the upper reaches of Lakhimpur only. Heavy rainfall in upper catchment has resulted in huge inflow in all the rivers of Greater Lakhimpur area in recent days.

On 5th June 2021, due to Flash Flood in the upstream reaches of Ranganadi, in a span of one hour, the water inflow at Ranganadi increased from 91 cumecs at 13.00 Hrs to 420 cumecs at 14.00 Hrs. After utilizing the full handling capacity of the reservoir, the remaining water was released into the river as per the “Standard Operating Procedure” (SOP) and observing full safety protocols and downstream warnings. The district administration was alerted instantly. Flood warning and alert system devised through the North East Space Application Station (NESAC), ISRO, The government of India is in use at the plant.

 

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