Abstract: In order to investigate the influence of reservoir sedimentation on the operation of Zhala hydropower station on Yuqu River of Tibet, we conducted overall physical river model test and researched the sediment accumulation process in an operation period of 50 years, the distribution and elevation of sediment deposition in front of discharge structures and water inlet of the power station, as well as the sediment characteristics through turbines. Research results suggest that in the end of the 50-year operation, the sediment of the reservoir area basically reaches scouring-deposition balance, with total deposition quantity reaching about66.45%of the reservoir capacity. The sedimentation elevation in front of the dam is almost equal to the elevation of water inlet bottom of bottom hole, posing little impact on sediment discharge through bottom hole. Moreover, apparent scouring funnel is formed in front of the power station inlet, indicating that sediment accumulation in approach channel has no obvious influence on water diversion of the power station. In initial impoundment period, the particle size of sediment through turbine is less than or equal to 0.1 mm, but in the end of the 50-year operation, coarse sediment (particle size larger than 0.1 mm) accounts for 3.2% of the total sediment through turbine. In the aim of reducing sedimentation and abrasion to the power units, we recommend to optimize the reservoir scheduling and to improve the sediment discharge efficiency in the next stage.

Key words: Tibet’s Zhala Hydropower Station, sediment deposition of reservoir, sediment deposition in approach channel of power station, sediment concentration, sediment through turbines, river model