Chamkharchhu III and IV will require construcion in protected areas and therefore is less prioritsed
Among the four hydropower projects designed in a cascading system along the Chamkharchhu, two have been prioritised.
While the construction of the 770MW Chamkharchhu-I is expected to begin soon, the Department of Hydropower and Power Systems is in the process of undertaking the preparation of the Detailed Project Report (DPR) of Chamkharchhu-II.
According to the draft environment and social management framework of Chamkharchhu-II, the project has been previously studied by the department through a reconnaissance study in 2011. A pre-feasibility report (PFS) was finalised in 2015.
Based on the findings and recommendations of the final DPR, the project will be proposed for development through Druk Green Power Corporation (DGPC).
The 590MW Chamkharchhu-II will be developed as part of a proposed cascade system. The Chamkharchhu-I HPP (770 MW) is the most downstream project in the country.
The Chamkharchhu-II diversion site will be located approximately 21km upstream of the first project. In addition, three other future projects are considered for the complete cascade.
The PFS of the 364MW Chamkharchhu-IV has already been conducted while no detailed study was conducted on the Chamkharchhu-III, which has the potential of generating 1,250MW of power.
However, the latter two projects are of lesser priority as it will require construction inside protected areas or biological corridors.
The recommended layout of the Chamkharchhu-II, according to the PFS, is a run-off the river scheme with an annual generation of 2420GWh. It comprises a gated intake dam 30m high, 8.9km head-race tunnel, underground powerhouse, and 0.3km tailrace tunnel.
The Chamkharchhu-II diversion dam axis is located near Shingkhar village and the proposed power house is near Nimzhong village.
River diversion is planned on the left bank, while the project is developed on the right bank
The draft framework also stated that the existing roads to Nimzhong and Shingkhar will be upgraded and will connect the powerhouse and dam site.
“The environmental impact on land, water, flora and fauna of the Chamkharchhu-II HPP is expected to be significant across the various project sites,” the report states.
A significant reduction in river flows would occur in areas further downstream. The primary areas of influence would be the upstream catchment area, the water storage area, the dam site, the tunnel corridors, plant room location, and the immediate area downstream of the dam and upstream of the power house.
Given the mountainous area and undulating landscape that is fairly untouched and pristine, the report states that erosion and sedimentation issues would need to be evaluated and managed in all areas during the construction, operation and maintenance.
As a result of influx in the workforce and changes to local livelihoods, it is stated that the project may indirectly increase pressures on forests and other natural resources.
The proposed project will also require land acquisition and possibly a small number of relocations. Given the sparse population in the project areas and the deep gorge of the reservoir area, these impacts are expected to be minimal according to impact screening of the pre-feasibility study. The 2015 study identified 26 households that could be affected.
The department is however in the process of identifying other social, cultural and environmental impacts that have not been documented.