13 Sep 2016

Supporting new hydropower plant construction in Bhutan with Reservoir Sedimentation Study

To harness Bhutan’s hydropower resources, Druk Green Power Corporation Ltd (DGPC), a public corporation of Bhutan, has commissioned DHI India to carry out reservoir sedimentation studies for a proposed construction of the new Dorjilung hydropower plant.

Construction of the new hydropower plant will take place on Kurichhu River at an elevation of 768m, with initial reservoir length of 6.8km, and depth of full reservoir level at 850m. The features of this proposed construction requires careful planning of design, operation and mechanism, including an essential need to understand sediment characteristics, its inflow, distribution and probable impact on the reservoir capacity.

Reservoir tip of Kurichhu river © DHI

Using data provided by DGPC, and DHI’s MIKE Powered by DHI software suite, a numerical modelling study of the conditions of the reservoir was determined. Data contributed by DGPC is analysed, synthesised and validated, as well as corrected before using as inputs for the study. This ensures that results from the study is an accurate assessment of real conditions of the reservoir.

MIKE 21C simulation result for Sediment Concentration Near Intake © DHI

Among the findings gleaned from the study was the assessment of the loss of reservoir storage over time, time taken to reach equilibrium level, optimal flushing strategy as well as the necessity of a separate desilting basin. With MIKE 11 and MIKE 21C, 1-D and 2-D study of the reservoir was carried to provide a comprehensive understanding of the reservoir in order for optimal operations of the proposed hydropower plant.

‘The study helps in the understanding of the sedimentation pattern of the reservoir over the years. It gives an insight of the efficacy of flushing and provides an estimate of the safe discharge for reservoir acting as a desilting basin. With the study, the different key levels of hydropower plant like fixing crest level and intake level can be finalised to ensure optimal operation of the hydropower plant.’ – Rajesh Kumar Mahana, Senior Water Resources Engineer, DHI