Responses of river sedimentation to water-sediment conditions in Inner Mongolia reach of upper Yellow River

The Inner Mongolia reaches of the upper Yellow River is facing the situation of severe sediment deposition caused by complicated factors. The sediment deposition processes of those reaches were calculated using sediment balance method which takes into account the sand blew from the deserts on both bank and the incoming sediment from the branches. The key affecting factors were analyzed by correlation analysis method. The results show that since 1952 the BYGL-TDG reaches in Inner Mongolia underwent the processes of accumulative sediment deposition,then relative balance,and accumulative sediment deposition again. The total sedimentation is 14. 230 2 × 108m3,of which the sedimentation quantity in July to October accounted for 81. 9% and that in the reaches from SHHK to TDG accounted for 83. 3%. The main affecting factor for the scouring and sedimentation of the reaches from BYGL to SHHK is the incoming water-sediment combination and the sand blew from the deserts. The critical conditions of non-scouring are the incoming sediment coefficient less than 0. 007 kg·s·m- 6. The main affecting factor for the scouring and sediment deposition of the reaches from SHHK to TDG is the incoming sediment from the ten hyperconcentrated tributaries on the south bank. The critical conditions to maintain non-sedimentation status are the comprehensive incoming sediment coefficient less than 0. 005 kg·s·m- 6,and the incoming sediment from the tributaries less than 0. 1 × 108 t. In general,the incoming sediment from the ten hyperconcentrated tributaries contributes the most to the sediment deposition.