Influencing Mechanism of the Operation of Xiaolangdi Project on Flow/Sediment Variation Rules in Yellow River Delta

Using methods combining statistical data analysis with practice discussion,the flow/sediment data of Lijin hydrological station and the influencing mechanism of Xiaolangdi on flow/sediment variation were analyzed.The results show that: Flow/sediment regulation of Xiaolangdi changes the annual distribution,the beginning phase of flood season advancing to June and the ending phase extending to November,the difference between flood season and non-flood season are getting smaller,the annual distribution of flow/sediment are tending to uniform,but in general,the annual flow/sediment are less 27.4%,72.1%,when compared with that in natural conditions;by adjusting the flow/sediment allocation,the ratio of flow/sediment and incoming sediment coefficient tend to normalize and rationalize(0.01 t/m3,0.01 kg·s/m6),and the flow/sediment combination is improved obviously,which is very significant for maintaining the dynamic balance of the estuary sand spit mouth and coastal in Yellow River Delta(YRD);Xiaolangdi project makes the YRD maintain a certain flow and flood peak(3 000~4 000 m3/s) all the year-round,which restrains effectively the occurrence of flow-break,moreover,sediment composition remarkably coarsens.