Bhutan’s Tala Dam Overtopped after unprecedented rainfall

Bhutan’s Tala Dam Overtopped after unprecedented rainfall

By South Asia Network on Dams Rivers and People on October 7, 2025

In a major scary incident, the Tala Dam on Wangchhu River in Chukha district of south Bhutan has overtopped for the first time ever, on Oct 5 following unprecedented rainfall in western Bhutan, prompting flood warnings for downstream areas in India’s north Bengal. Bhutan’s NCHM confirmed that DGPC reported that the dam gates failed to open, leading to river water flowing over the dam, considered most dangerous situation for any dam as dams are not designed for such an eventuality.

Following continuous rains on Oct  4 & 5, the Bhutan Ministry of Energy and Natural Resources reported that the Wangchhu river inflows dramatically surged from under 200 m3/sec at 4 AM on Oct 5 to around 1,260 m3/sec by 11 AM, causing water to spill over the dam at about 7 AM on Oct 5. At the time, two of the four radial gates were partially open, and the Tala powerhouse was generating at 1020 MW plus 10%. Druk Green Power Corporation (DGPC) said the situation remained the same as of 12:30 PM on Oct 5. By 8 pm, the overtopping continued. The Tala HEP resumed partial operation with one unit remaining under repair.

In a video report, DGPC MD Dasho Chhewang Rinzin said that power supply went off when the dam operators were trying to open the Tala dam gates in response to fast rising dam water level and they had by then partially opened two of the gates. This also shows that the alternate manual game opening mechanism either did not work or there was no time for that as the dam gate opening was started too late. This raises further question marks over the functioning of dam safety mechanisms.

Other Projects affected The projects adversely affected in Bhutan during the current phase include Succhhu, Punatsangchhu-II, Chukha and Dagachhu. The Mangdechhu, Basochhu and Kurichho HEPs remained in operation under careful watch. At the Nikachhu HEP, a blockage to access is reported, but no damage to project dam or power components is reported.

By 8 pm on Oct 5, water flow at the upstream (from Tala HEP) Chukha HEP reduced to 600 m3/sec, the Chukha project remained shut down due to intake choking. Dagachhu project remained shut down as a precautionary measure. Suchhu project remained offline due to transmission failure. Punatasangchhu-II HEP gates are open and is down due to high sedimentation.

No casualties have been reported, as overnight duty staff were evacuated in time. Bhutan’s National Centre for Hydrology and Meteorology (NCHM) has alerted West Bengal authorities to the potential impact. The area borders Toto Para, the home of the near-extinct indigenous Toto tribe. If the Tala dam collapses, it is feared to wipe out Toto Para, Hasimara, Madarihat, and a large part of Alipurduar district. The National Disaster Response Force (NDRF) said its team based in Alipurduar has been put on “highest alert”. All personnel on leave were recalled, while an additional 15 rescuers from RRC Siliguri are being deployed to reinforce ground response.

The alert comes as north Bengal continues to recover from landslides and flooding caused by heavy rains, which have killed at least 27 people and damaged roads and infrastructure. Officials warn that rivers could rise rapidly, increasing the risk of flash floods in the Dooars region.

The extent of the damage at the Tala HEP and further downstream will only be known once the floods subside and assessment is done. The Bhutan Govt and DGPC, it is hoped will commission an independent assessment of the whole event, particularly the safety aspect of the Tala dam, lessons to be learnt and implemented. - SANDRP