The Upper Tamakoshi hydroelectric power station is a 456MW run-of-the-river project under construction on the Tamakoshi River in the Dolakha District, approximately 200km away from Kathmandu, Nepal.
Construction on the Upper Tamakoshi hydropower project was started in 2011 and was expected to be completed within six years. The project’s progress was, however, hampered due to an earthquake in April 2015. The facility is currently scheduled for commissioning by the end of 2019.
The developer and operator of the project is Upper Tamakoshi Hydropower Limited, an autonomous company established by Nepal Electricity Authority (NEA) in March 2007.
The Upper Tamakoshi hydropower station is expected to produce 2,281GWh of electricity a year.
Upper Tamakoshi hydropower plant make-up
Upper Tamakoshi comprises a 22m-high and 60m-long concrete dam, two 225m-long de-sanding basins, an 8.4km-long headrace tunnel with 32.14m² of cross-sectional area, and an underground powerhouse (142m-long, 13m-wide, and 25m-high) equipped with six Pelton turbine units.
The gross head height of the dam is 822m. Design flood and discharge capacities for the facility will be 885m³/s and 66m³/s, respectively.
Live storage capacity of the dam will be 1.2 million cubic metres. The 2.9km-long tailrace tunnel of the project will have a cross-sectional area of 35m².
Transmission and power purchase agreement
The power generated by the Upper Tamakoshi hydropower plant will be fed into the national grid through a 49km-long double circuit 220kV transmission line between Gongar and the Khimti power station.
The Nepal Electricity Authority (NEA) and Upper Tamakoshi Hydropower Limited signed a draft power purchase agreement (PPA) for the project in 2011. The NEA agreed to purchase the power output of the plant at a yearly average rate of NPR3.50 a unit.
Norconsult and Lahmeyer provided detailed project design, construction management and monitoring services for the project.
The civil works contract for the project was awarded to Sinohydro Corporation. Andritz Hydro was awarded the contract for the design, manufacturing, and supply of electromechanical equipment, including turbines and generators for the project.
KEC International was contracted for the supply and erection of transmission lines as well as the substation.
Texmaco, an engineering and infrastructure company based in India, was engaged for the hydro-mechanical works for the project.
The total construction cost of the project was estimated to be NPR35.29bn ($441m) in 2011. Loans were extended by Nepal’s Employees’ Provident Fund ($131.6m), Nepal Telecom ($78.97m), Citizen Investment Trust ($26.32m), and Rastriya Beema Sansthan (RBS, $26.32m) to finance the project.
The Government of Nepal committed to providing a loan of up to NPR11.08bn ($145.8m) for the project.
The project cost has been reportedly escalated by $41.8m due to the delay and disruption caused by the 2015 earthquake.