Based on measured data of the Wanjiazhai Reservoir in different periods, the characteristics of the spatial and temporal distribution of sedimentation in the reservoir area were preliminarily analyzed and the impact of reservoir operation on this distribution was discussed. Primary conclusions are as followed: in terms of temporal distribution, sedimentation continuously accumulated over the period from 2000 to 2017, with the sediment deposition ratio dramatically decreasing between 2011 and 2017; in terms of spatial distribution, the sedimentation in the reservoir area was mainly concentrated downstream of the WD54 section, with the highest concentration being downstream of the WD23 section. The characteristics of sedimentation distribution in the reservoir area were closely related to inflow and sediment conditions and reservoir operation water level. When the water level was lower than 952 m, the sediment deposition ratio was lower than 0. To further improve the sediment deposition form in the reservoir area, lowering water level and ejecting the sediment are recommended in a timely manner.

Sediment discharge method has great impact on the service life and comprehensive benefits of the reservoirs in sediment-laden river. In this paper, the actual operation process of Wanjiazhai Reservoir in 2018 was taken as the research object to analyze changes in runoff and sediment process and erosion and deposition in the reservoir area, and to explore possible influencing factors for reservoir sediment discharge. According to the results, the erosion in the reservoir area of Wanjiazhai Reservoir in 2018 was 112.6 million t, the erosion period was concentrated in August and September, and the erosion positions were concentrated at the elevation of 935-966 m; the deposition morphology in the reservoir area changed obviously after twice sediment flushing in 2018, and the channel has been subject to deepening and widening accompanied by reservoir bank collapse; there is a negative correlation between the outflow sediment concentration/sediment discharge ratio of the reservoir and the reservoir water level.