Morphological computation of a cascade system of dams using delft3d-fm coupled with a real-time control tool

This paper presents detailed hydraulic and morphological study of a cascade system of dams, located in Marsyangdi River in Nepal. Firstly, severe morphological problem in one of the dams, namely Middle Marsyangdi Hydropower Project (MMHPP), was studied. We revealed one of the key reasons of the problem, which is related to the ignorance of largeand meso-scale morphological feature of the river while selecting the site. Secondly, the sedimentation process at the reservoir was replicated using a two-dimensional morphological model, namely Delft3D-Flexible Mesh (D-FM) coupled with Real-Time Control (RTC) tool to simulate reservoir gate operation. We attempted to incorporate downstream dam in the model, namely Marsyangdi Hydropower Project (MHPP), to simulate synchronized operation and its morphological impact. The effect of synchronized operation of two dams was assessed by simulating different synthetic flushing scenarios. Sensitivity of two different sediment transport formulae (Ashida-Michiue and Engelund-Hansen) on the model results was assessed as well. Given a rapid modelling exercise of such complex system using D-FM, the results can be regarded as satisfactory. They showed consistent model behaviour and observed trend despite the complexity involved in morphological modelling with synchronized operation of two dams. The study can further be improved in case more data and information are available. The model can also be applied to optimize dam operation considering morphological and ecological impacts on downstream reach.