Guwahati, Oct. 28: Thousands of gallons of water from overflowing dams in Arunachal Pradesh and neighbouring Bhutan gushed down to the plains of Assam late last night, affecting thousands of people.

Diwali was a washout in the central districts of Lakhimpur and Sonitpur and Kamrup district in Lower Assam.

Lakhimpur and Sonitpur were buffeted by water from an overflowing dam in Arunachal Pradesh, while Kamrup was flooded after Bhutan released excess water from the Kurisu dam. The Arunachal dam belongs to the North Eastern Electric Power Corporation (Neepco).

The low-lying areas in north Lakhimpur sub-division, Nameri tiger reserve in Sonitpur district and Puthimari in Kamrup district were the worst hit.

Lakhimpur circle officer Hemkanta Pegu said 40,000 people were affected in 35 villages. Two wards of Lakhimpur town were also flooded.

“It started around 8 last evening. Heavy rain over the past three days and the water released from the Neepco dam in Arunachal Pradesh caused the flash floods. We are trying to help the people as best as we can,” he said.

The floods have worsened the breaches in the embankments caused in the June rainfall, mainly in Ujani Pohumara, Ujani Thamti and Bogolijan. “Repair of the breaches was supposed to start in December,” Pegu said.

Jatin Bora of Thamti said their Diwali was ruined. “What can we do?” he asked.

M.S. Jyrwa, general manager, Neepco, said the spill from the pondage (water held in a reservoir for a short period to supply to a hydel plant) at the 405MW Ranganadi project at Yazali in Lower Subansari district of Arunachal Pradesh, started around midday.

Speaking over phone from the project site, the official said there was no control over the excess water in such schemes. “The design of the pondage is such that the gates will automatically open to drain out water in excess of the capacity of the reservoir,” he said.

A similar disaster was unfolding in Puthimari in Kamalpur sub-division of Kamrup district around 11.30pm after Puthimari river overflowed following heavy rainfall and release of water from the Kurisu dam in Bhutan, bordering Baksa district.

Traffic went haywire on National Highway 31. This is the third wave of floods this year to have hit Puthimari, where work is on to repair breaches in embankments.