Abstract
This paper presents a sediment management study through hydraulic flushing of a reservoir at a hydropower station in Kashmir, Pakistan. The study area is under the influence of monsoon rains and is part of a seismically active region along the northwestern zone of Eurasian plates. The earthquakes, glacial melts, rainfall events, along with some anthropogenic factors aggravate the sediment load in the streams. Since small reservoirs are sensitive to sedimentation, periodic flushing is required. The research methodology uses 1D river sediment model HEC-RAS to simulate a number of scenarios impacting the sedimentation rate and flushing efficiency and provision of a check dam upstream of the reservoir. Different flushing scenarios were formulated based on likely flows and assessed through three criterions: enhancing life of the power plant by keeping sediment level below the power intake level, preventing abrasion of turbines by the fine sediment particles and ensuring continued power plant operation after a flushing by checking that the flushed material does not block outflow from the tailrace. Results show that without flushing the dam would be filled up in 15years of operation under the normal flow conditions, whereas life of the reservoir will be enhanced manifold with regular flushing leading to a significant reduction in the quantity of sediment sizes that are likely to degrade the turbines. Simulated scenario of providing a check dam upstream of the reservoir revealed that it is helpful in mitigating the flood risk to the surrounding area.