A section of weak rock collapsed inside a tunnel at the Tarbela Fifth Extension hydropower project on Monday, 9 November, letting water from an intake pit surge into the tunnel and the powerhouse under construction. Work on the expansion has been suspended indefinitely. Pakistan's Water and Power Development Authority, WAPDA, said all workers were evacuated safely and nobody was hurt or killed.
WAPDA said the failure happened while crews were excavating the second bench of a connecting tunnel. Officials at the site said about 1,000 cusecs of water already in the tunnel flowed out of the intake pit and flooded the construction area. WAPDA says the pit has since been drained, no more water is entering downstream work areas, and pumping of the powerhouse has begun. The authority rejected reports that the main tunnel had collapsed and said the main tunnel, the powerhouse, the tailrace culvert and the switchyard are undamaged. The deputy commissioner of Haripur, Waseem Ahmed, also dismissed social media claims that the dam had broken. Senior authorities have ordered an inquiry.
Releases and flood alert
As a precaution the Indus River System Authority decided to lower the Tarbela reservoir by six feet, from 1,496 to 1,490 feet. Releases were raised from 55,000 cusecs to about 144,200 and are expected to stay near 150,000 cusecs around the clock, far above the 55,000 cusecs the provinces currently need. The extra water is being stored at Chashma Barrage. The Khyber Pakhtunkhwa disaster management authority told the administrations of Haripur, Swabi and Nowshera to take precautions over the next 24 hours and watch riverbank settlements, and set up a helpline, 1700.
A project with a record of setbacks
The fifth extension converts a tunnel previously used only for irrigation into a power tunnel. It will add 1,530 MW through three 510 MW units, lifting Tarbela's installed capacity from 4,888 MW to 6,418 MW. The World Bank is providing 390 million dollars and the Asian Infrastructure Investment Bank 300 million. In June the World Bank approved another 300 million to cover overruns. A Chinese contractor won the 354.6 million dollar civil works contract in May 2021.
The project was meant to take five years, with first power in 2027. Planning Commission documents show repeated trouble. In August 2025 rising reservoir levels and inflows flooded parts of the site, a cofferdam collapsed and construction stopped, with unauthorised design changes named as a major cause. The estimated cost rose by more than 285 per cent, from Rs 82 billion to Rs 317 billion, and the commission estimated that the 30-year cost of generation could reach Rs 27 to 28 a unit, which could make the project economically unviable. In January this year, with physical progress at 56 per cent, WAPDA's chairman was told the first unit would start in April 2027.
Dewatering, inspection and repair could take several months, which puts that target at risk. WAPDA has not answered questions about a revised timeline or the cost of the damage.
