The Tanahu hydropower project achieved a significant milestone at the end of last year with the successful initiation of the river diversion around the dam site. The project, situated approximately 150km west of Kathmandu, boasts a storage-type hydropower design, aiming for a planned installed capacity of 140MW and an estimated energy generation of 585.7GWh within its first decade.

The project’s concrete gravity dam, standing at 140m, will be the largest of its kind in the country, accompanied by a storage reservoir with a total volume of approximately 295 million m3.

The river diversion ceremony on November 6, 2023, marked a key juncture in the Tanahu hydropower project's progress. Hydro experts from Tractebel, in collaboration with Canadian-based Manitoba Hydro International, played a crucial role in various aspects of the initiative, including the preparation of tender documents, tender evaluation, construction supervision, design checks, and advisory services during project operation and maintenance.

Construction of the Tanahu hydropower project commenced in 2018, and it is anticipated to be commissioned in 2026.

As of now, the Seti River, en route from the Annapurna Massif to the Bay of Bengal, has been successfully diverted around the dam foundation pit. Once the dam is completed according to schedule, the diversion tunnels will be permanently sealed. The dam is envisioned to create a substantial reservoir, serving as a buffer for the fluctuating river flow, ranging from tens of m3/sec during the dry season to several thousand m3/sec during the monsoon season from July to October.

Designed to operate at peak efficiency during the driest months of the year, the Tanahu hydropower project aims to generate renewable electrical energy year-round for several hours per day. This is expected to play a pivotal role in enhancing Nepal's seasonal energy security, concurrently reducing reliance on imported energy sources.

Recognizing the project's national significance, Dr. Frank Zollner, Acting Project Manager, Tractebel in Germany, stated: "The Tanahu project is characterized by its multidisciplinary nature, with a large gravity dam, several kilometers of tunnel systems, and an underground power plant of considerable size. The river diversion represents an important milestone, benefiting not only Tractebel and its partners but also Nepal, one of our most important markets for hydropower development. The renewable, sustained energy provided by Tanahu will greatly benefit the Nepalese people and economy, stabilizing the national grid and contributing to economic growth through energy exports to neighboring countries such as India."

by waterpowermagazine