Economic Analysis of Sediment Management Strategies for Techi Reservoir

Abstract

Since the Techi Reservoir was built in 1974 has no sediment management strategy The reservoir has lost 25% of its storage capacity due to sedimentation To find the most efficient sediment management strategy it is important to incorporate economic analysis in order to compare the costs and benefits of different strategies This study used the RESCON2 model to simulate reservoir life and economic benefits under different scenarios for three different strategies: flushing dredging and bypass method by calculating costs and simulating long-term effects in order to help decision-makers formulate the most appropriate management plans The different scenarios included changing the implementation scheduling of each method and parameters that affect the efficiency of the sediment management strategy In addition this study built a hydrological conceptual model to simulate how much time and what parameters are needed to bring the water level down to the level needed for flushing The RESCON2 simulation results show that only the flushing method will extend the reservoir’s life by more than 300 years Flushing also resulted in the highest aggregate net present value converted from the maximum water yield in the remaining storage capacity which came out to a total value of about 3 2 billion US dollars In addition the hydrological conceptual model shows that a fixed water level of 1315m and a flow of 57cms it will take at least 90 days to effectively reduce the water level to the specified level needed for flushing to occur This means that flushing is feasible but requires planning and preparation The aggregate net present value of dredging and bypass are about 2 3 billion and 2 billion US dollars Because the model results show that the amount of sediment able to be desilted by dredging is more than bypass and the cost of dredging is significantly lower than bypass due to the high construction costs needed for bypass the efficiency of dredging seems to be higher However this may not be the case in all scenarios The simulation result for bypass is the more conservative than dredging as there are more factors which must be assumed For instance the amount of desilting possible by bypass is determined by the operation time and the technology used to discharge the sediment Another aspect of this research that requires further discussion is the declining discount rate This research used a declining discount rate of 6% as recommended by the World Bank and Taiwan experts But it may be important to consider economics hydraulic engineering and climate change together to check that this is in fact an appropriate value

Date of Award	2019
Original language	English
Supervisor	Hsiao-Wen Wang (Supervisor)