The project will be built on the Kotmale oya a tributary of the country’s longest river Mahaweli. The plant will be located upstream of the existing 201MW Kotmale reservoir, the uppermost impoundment of the Mahaweli cascade. The plant harnesses a gross head of 491m available between upper reaches of Kotmale oya and the existing Kotmale reservoir high water level. The main inflow of the Kotmale oya is to be augmented by diverting water from several streams in the same basin.

The project involves construction of the 35.5m high main dam, water conveying and access tunnels, surge and pressure shaft, steel lined penstock, underground power house cavern, and weirs and tunnels used for diversions. The electromechanical equipment includes two turbine generator units, each with a 75MW capacity.

The preliminary works to be commenced shortly includes construction of access roads to the main construction sites, housing, office complexes and recreational facilities for the construction staff, housing and infrastructure facilities for re-settlers, and the provision of electricity supply to the project area.

CEB has introduced a comprehensive environmental management programme in planning the project and it is scheduled to effect number of mitigatory measures to minimise the environmental impacts during and after the project implementation. The work has already begun with regard to the biodiversity assessment and the watershed management plan. The resettlement action plan has already been finalised.

Upper Kotmale – funded by Japan Bank for International Cooperation (JBIC) – is expected to generate 528GWh annually.