Lower Apsuwa Hydropower Project (LAHPP) is a 54 MW run-of-river project located in Makalu and Silichong Rural Municipalities of Sankhuwasabha district in Koshi Province. Developed by Mizu Energy Limited, the project utilizes a net head of 619 m and a design discharge of 10.22 m³/s at Q40% exceedance.
Project Area
Headworks components are located in Silichong Rural Municipality while powerhouse components are located in Makalu Rural Municipality, between 27°30’49” to 27°33’35” N latitude and 87°10’48” to 87°14’00” E longitude. The area is about 50 km road distance to the north of Khandbari, the district headquarters of Sankhuwasabha. All the major project components of the headworks are located along the right bank of the Apsuwa Khola while the penstock alignment and powerhouse area are located on the right bank of the Arun River.
Tumlingtar Airport is the nearest airport from the project area. There are daily flights to this airport from Kathmandu.
Pukhuwa, near the powerhouse site, is electrified by the construction power of Arun-3 project. Pukhuwa is well connected with NTC cellular network which have both voice and data service. The village of Yangden near headworks have unreliable cellular network which is limited to voice only. There is no telecommunication network at the headworks site.
Hydrology
The catchment area of Apsuwa Khola at headworks extends over 202 km² with elevations from 1,562–6,881 m. Average flow at the intake is 16.8 m³/s, with a dependable flow of 10.22 m³/s. Floods are estimated at 328 m³/s (100-year return) for headworks. A minimum 10% environmental flow is allocated for downstream ecology.
Geology
The project area is located in the Lesser Himalaya, dominated by gneiss and schist. The 3.5 km headrace tunnel passes mainly through strong gneiss with localized weathered zones.
Project Configuration
Water is diverted from Apsuwa Khola through an intake and gravel trap, conveyed via a 2,498 m headrace tunnel, a 7 m × 26.7 m surge shaft, and a 1,524 m penstock to the underground powerhouse.
Powerhouse will be equipped with 3 Pelton turbines (18 MW each) and 2 generators (21.18 MVA). A 350 m tailrace cut-and-cover culvert returns water to the Apsuwa Khola.
This project will have switchyard with two 11/132 kV, 30 MVA transformers, and an 18 km long, 132 kV double-circuit transmission line connecting to Sitalpati substation of NEA.
Energy Generation
The project will generate about 341.69 GWh annually, including 119.58 GWh in dry season and 222.11 GWh in wet season.
Construction
Construction will be implemented under an EPC contract, the total construction period is estimated at 3.5 years.