Estimation of hydropower potential of Kuru ganga at Bopathella

Abstract

In Sri Lanka, the power generating system is predominantly based on hydropower which has provided approximately 90% of the total demand in the recent past. The government of Sri Lanka is encouraging not only the development of large hydropower schemes, but also mini and micro hydropower systems.

Kuru Ganga mini hydropower project plans to exploit the head of 'Bopath Ella' waterfall which is located on Kuru Ganga, a tributary of the river Kalu Ganga. Gauged data at an adjacent catchment Deraniyagala on the river 'Seethawaka Ganga' were extrapolated to obtain streamflow at Bopath Ella, using rainfall, topography, land use and soil characteristics of the two watersheds. Missing streamflow data at the gauging station Deraniyagala was filled using a mathematical watershed model based on the Tank Model. Data extrapolated for Bopath Ella catchment was incorporated into a water balance model to compute the hydropower availability.

The daily flow duration curve at Bopath Ella was used to estimate the appropriate downstream water releases. Based on this, a suitable level of water release for maintenance of the waterfall aesthetics and the riparian environment was established. A simple computer spreadsheet was developed considering water balance at the weir pond estimating river flow for power generation. River inflows, rate of evaporation, water releases for riparian area sustenance etc, were considered in the water balance computations. Extractable power from the estimated streamflow at Bopath Ella was computed assuming a turbine capacity of 10 cumecs.