A morphological study of a cascade system of hydropower dams is conducted, namely Middle Marsyangdi (MMHEP) and Marsyangdi (MHEP) in Nepal. These two plants provide more than 20% of the total energy. However, the upstream reservoir (MMHEP) has been suffering from significant sedimentation problem since its commissioning as it has lost more than half of its storage capacity just within 4 years of exploitation. Current study is mainly focused on modelling and analysis of sedimentation problems, particularly at MMHEP, that can be attributed to the consequences of ignoring the river planform and sediment inflow while selecting the reservoir site. Morphological process at MMHEP as well as downstream river reach and MHEP has been modelled using Delft3D model with Feedback Control Tool to simulate synchronized operation of two reservoirs in a cascade system. Effects of flushing operation as well as sensitivity of different sediment transport formulae on simulation results have been revealed and analyzed. The results show consistent model behavior and trends despite the complexity involved in morphological modelling with synchronized operation of two reservoirs in a cascade as well as data scarcity. Recommendation has been made for further improvement of the models based on proper data and information in future. For details please refer to the attached paper that was presented in ICOLD2019 (http://www.icold-cigb2019.ca/).
Figure 1. Sediment deposition near the intake area, observed during October 2009 (lower picture, Kayastha, 2010), deposition seen during drawdown for the dredging work in 2010 (upper right), and upper graph shows change in cross-section, located about 70 m upstream of the dam (Shrestha, 2012) |
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