Tamor Storage HydroElectric Project

Evolution of Tamor Storage HydroElectric Project

In 1985, the Japan International Cooperation Agency (JICA) proposed a substantial 696MW hydroelectric project on the Tamor River, involving the construction of a 153-meter tall dam. However, the government at that time did not express much interest in pursuing the project. Moving ahead to 2012, the Nepal Electricity Authority (NEA) filed an application with the Department of Electricity Development (DoED) following a study conducted by JICA. The aim was to obtain a survey license for the project.

Initially, the DoED showed reluctance, expressing concerns that the proposed hydropower project might adversely affect existing ventures such as the 38MW Kabeli A and 22MW Lower Hewakholawhich already held electricity generation licenses. In response to this, NEA adjusted its approach and applied for a survey license for the construction of a scaled-down 200MW project on the same Tamor River. This modified proposal was eventually approved. Subsequent studies conducted on the project hinted that it could be upgraded to generate a more substantial 762MW of electricity. In August 2013, the Department of Electricity Development extended a survey license to NEA, enabling various studies for the development of the 200MW project on the Tamor River. The subsequent findings suggested the project’s potential for an even higher capacity.

On January 19, 2020, a significant development occurred with the signing of a Memorandum of Understanding (MoU) between the Office of the Investment Board Nepal (OIBN), Power Construction Corporation of China (PCCCL), and Hydroelectricity Investment and Development Company Ltd. (HIDCL). The MoU outlined plans for a detailed feasibility study (DFS) for the Tamor Hydropower Project, which was now envisaged at a capacity of 756MW. This ambitious project was first identified in the master plan prepared by JICA in 1985. It is situated on the Lambhu Khola of the Tamor River, located at a Latitude of 27°03'11.9"N and Longitude of 87°32'56.5"E, spanning Tehrathum and Panchthar districts in Province 1. The project area, approximately 650 km east of Kathmandu, is accessible via Mechi Highway from Jhapa, Puspalal Highway from Panchthar, and Tamor Corridor from Dharan to Taplejung. Reservoir Area

The Tamor river basin originates in Mount Kanchanjunga and flows to form the Saptakoshi river, eventually merging with the Ganga River in India en route to the Indian Ocean. The Tamor Storage project holds significant potential, especially for Eastern Nepal, promising to reduce dependency on electricity from other provinces and contribute to local economic prosperity. NEA’s preliminary report suggests that the geographical location, social impact assessment, and environmental conditions are suitable for the construction of the project. However, the presence of two hydropower projects upstream poses a major obstacle, as these projects would likely be submerged if the Tamor Storage project moves forward.

According to Baburam Bhardwai who is a Chief Technical Officer (CTO) at Hydro Venture Pvt Ltd, “Tamor storage project (752 MW)is far more attractive and economicaly/financially viable multi-purpose project of Nepal. This project should have been implemented for generation, irrigation and recreation benefits long back. It is already late; sooner the better.” Civil engineer Kushal Basnet, in an article for myRepublica, highlighted that the generated power from the Tamor Hydropower Project could be exported to either India or Bangladesh. This export could be facilitated through a transmission line constructed from the project site to Inaruwa via the Kakarbhitta border, with the construction cost potentially lower due to the project’s proximity to the market.

Project Details

The Tamor Storage Hydroelectric Project, identified as a Storage type hydropower initiative with a capacity of 756 MW according to the NEA feasibility study in 2016, holds significant promise for the energy landscape in Nepal. Situated in Province 1 across Tehrathum and Panchthar districts, approximately 650 km east from Kathmandu, this venture is a focal point for sustainable energy development in the region. The closest town to the dam site is Myanglung Bazaar, accessible through a 20km drive on an earthen road.

Project Features (NEA Feasibility Study):

  1. Project Layout:

    • Rock Fill Dam: Positioned at the riverbed.
    • Chute Spillway: Incorporated for controlled water release.
    • Headrace Tunnels: Four tunnels designed to divert water from the dam to the powerhouse.
    • Penstock Pipe: Conveys water from the headrace tunnels to the underground powerhouse.
    • Underground Powerhouse: Located on the right bank, approximately 150m downstream of the dam toe.
    • Turbines: Four units with a total installed capacity of 756 MW (194 MW each).

  2. Climate:

    • Southwest Monsoon: Lasts from June to the end of September.
    • Altitude Influence: Climate strongly influenced by altitude changes over short distances.
    • Rainfall Distribution: Approximately 80% of rainfall occurs during the monsoon.

  3. Geology:

    • Thrusts: Identified upstream and downstream of the proposed Headworks and powerhouse location.
    • Shear Zones:
      • Thick Shear Zone: Located about 2 km upstream of the proposed dam axis.
      • Thin Shear Zone: Identified on the left bank of the Tamor River, around 80m upstream of the proposed dam axis.
      • Shear Zone Orientation: Strikes along N-S with an average slope of 200 due southwest.

  4. Hydrology:

    • Catchment Area: 5094 km².
    • Average Flow: 310 m³/s.
    • Design Flow: 657.4 m³/s.
    • Hydrological Stations (DHM):
      • Station 684: Majhitar.
      • Station 690: Mulghat.

Technical Components of the Hydropower Project:

  1. Diversion:

    • Three Inverted D type diversion tunnels.
    • Diameter: 11m.
    • Average Length: 1.5 km.
    • Diversion Discharge: 1667.67m³/sec per tunnel.
    • Earthen Cofferdam: Around 70m height.

  2. Dam:

    • Rock fill type with an impervious clay core.
    • Height: 210m.
    • Crest Elevation: 558 masl.
    • Crest Length: 550m.
    • Gate Controlled Chute Type Spillway: Elevation of 530 masl.

  3. Reservoir:

    • Full Supply Level: 550m.
    • Minimum Water Level: 492m.
    • Dead Storage Level: 475m.
    • Live Storage: 1900 MCM.

  4. Intake:

    • Four sloping intakes.
    • Minimum Operating Level: 492m.

  5. Waterway:

    • Headrace Tunnel: 6.5m diameter, around 1km long (four Inverted D type).
    • Vertical Shaft: Four, around 130m long.
    • Penstock Pipe: Four pipes, average length 100m, diameter 6m.

  6. Powerhouse:

    • Underground power station.
    • Location: 150m downstream of the dam toe.

  7. Turbine:

    • Four 194MW rated Vertical Axis Francis turbines.
    • Gross Head: 198m.
    • Rated Turbine Net Head: 169.73m.
    • Rated Discharge: 129.75m³/sec.
    • Centre Line of Turbine: 347m.
    • Tail Water Level: 352m.

  8. Tailrace:

    • Inverted D type Tailrace tunnel.
    • Diameter: 8m.
    • Discharge: Flow back to the Tamor River.

  9. Energy Generation:

    • Powerhouse operates 6 hours in dry season, 24 hours in the wet season.
    • Annual Electricity Generation: 3353.85 GWh.
    • Wet Season: 2248.1 GWh.
    • Dry Season: 1105.75 GWh.

  10. Power Evacuation:

  • 400 KV double circuit transmission line.
  • Power transmitted to proposed substation at Inaruwa, Sunsari district.
  • Transmission Line Length: Around 75km.

References

  1. Nepal in Data. “Tamor Storage Hydroelectric Project.” Link
  2. Investment Board Nepal. “Detailed Feasibility Study of Tamor Hydropower Project.” Link
  3. The Kathmandu Post. “NEA mulls building 762MW project on Tamor River.” Link
  4. My Republica. “Tamor Storage Hydro Project: A Game-Changer for Eastern Nepal.” Link
  5. Nepal Energy Forum. “Tamor Hydro Project Capacity Reduced to 200 MW.” Link
  6. Khatri Dickembs, and Vishnu Prasad Pandey. “Climate Change Impact on the Hydrological Characteristics of Tamor River Basin in Nepal Based on CMIP6 Models.” (2021)