Influence on sediment deposition and morphology evolution in Qingyanzi reach caused by the change of water silt conditions of TGP

The change of water silt condition and operation regulation will have a great influence on the deposition in Qingyanzi reach.The field data after the reservoir impounding and the previous studies of feasibility stage show that the locations of sediment deposition are not changed,while the quantity and area of deposition are reduced.In this work,a two-dimensional model that is calibrated by the field data after reservoir impounding is used to simulate the influence on the deposition caused by the changes in water silt condition.The calculation results show that the deposition in 1960s agrees with the previous studies,while the quaitity and area of deposition in 1990s are reduced and river pattern transformation is postponed until 1990s.Along with more reservioirs completed in the upstream,the deposition rate is further decreased relative to that in 1990s,but river pattern trasnformation still occurs.The changes in water silt conditions only cause a change in deposition rate,while the deposition location and the trend of morphology evolution are not changed.A navigation difficulty could still appear in the locations of main flow translocation with the lateral branch.