The catastrophic Bhotekoshi floods on August 26 damaged more than a dozen hydroelectric projects, compelling the Nepal Electricity Authority to run the country’s primary backup power station, the reservoir-based Kulekhani, round-the-clock during the peak rainy season.

The emergency run has brought the project under severe operational stress. Traditionally reserved exclusively for the dry winter months to balance the national grid, all three cascading powerhouses of the Kulekhani scheme are currently generating electricity continuously to offset the loss of more than 400 megawatts of power knocked offline in Rasuwa and Nuwakot districts.

“The catastrophic flood completely crippled several major power plants in the central region,” said Pralhad Raut, chief of the Kulekhani-I Hydropower Project. “Because over 400 megawatts of generation capacity suddenly went offline, the grid management ordered Kulekhani and other operational facilities to immediately step in and bridge the deficit.”

The continuous operation of the reservoir-based scheme is consuming water at a rapid rate. The Nepal Electricity Authority’s internal monitoring revealed that the water level in the Indra Sarobar reservoir is dropping by 20 to 25 centimetres daily due to continuous generation, while incoming streams replenish only 15 to 18 centimetres per day. As a result, the reservoir is seeing a net decline of 2-10 centimetres a day.

By 2 pm on Friday, the water level at Indra Sarobar, Kulekhani’s reservoir, reached 1,522.46 metres. The reservoir has a maximum structural capacity of 1,530 metres. However, structural limitations prevent the utility from filling the reservoir to its full capacity.

Following the devastating April 2015 earthquake, cracks were detected along the main dam. Detailed engineering inspections conducted by Japanese dam experts recommended maintaining a maximum safe operational threshold of 1,527 metres. Consequently, utility engineers exercise extreme caution once water levels reach this limit to prevent structural failure.

“Under normal circumstances, Kulekhani would never be operated continuously during the monsoon peak, and the reservoir would have filled to capacity by now,” said a senior official at Kulekhani-I, speaking on condition of anonymity. “However, the sudden loss of generation in Rasuwa and Nuwakot left the authority with no choice. We are running all three plants 24 hours a day despite the long-term risk to our winter reserves.”

The Kulekhani complex operates as a three-stage cascade system located in the Indrasarowar Rural Municipality in Makawanpur district. Water released from Kulekhani-I generates 60 megawatts, which then flows directly into Kulekhani-II to produce another 32 megawatts, and finally through Kulekhani-III to add 14 megawatts, delivering a combined total capacity of 106 megawatts to the national grid. Currently, one generator at Kulekhani-I is undergoing scheduled maintenance, while the remaining operational generator continues running at peak output to drive all three stations down the cascade.

The unseasonal depletion comes at a time when Kulekhani is already battling a severe decline in overall storage capacity. Heavy siltation and sediment buildup have eroded the reservoir’s operational lifespan for decades. According to recent technical assessments, the effective storage volume of the reservoir has shrunk dramatically due to continuous siltation.

When Kulekhani-I was commissioned in 1982, the reservoir possessed an active storage depth of 57 metres and a total capacity of 85.3 million cubic metres of water, producing up to 211.1 million units of electricity annually. However, devastating floods in July 1993 dumped millions of tonnes of debris into the reservoir, raising the lake bed by six metres overnight and permanently reducing the usable water depth to 50 metres.

Subsequent studies by Nepal Electricity Authority engineers confirm that the lake bed now holds over 170,000 cubic metres of accumulated silt, sand, and gravel. As a result, the usable water depth has dwindled to approximately 46 metres, and the total storage volume dropped to 59.99 million cubic metres five years ago. This capacity reduction has cut the annual energy generation potential by over 66.4 million units, down to just 144.7 million units.

Engineers warn that fully restoring the reservoir’s lost capacity would require draining Indra Sarobar completely to dredge the deep sediment—an expensive process that would disrupt grid stability for months.

Constructed at an initial cost of 12 million US dollars, the reservoir was designed with a structural lifespan of 50 years. With its usable water zone now restricted below 1,483 metres, the ongoing emergency discharge threatens to leave the country vulnerable to acute power shortages this winter.