Runoff Limit in the Yangtze River Estuary during Flood Season

The issue about extending area of Yangtze River Diluted Water is widely concerned. Through introducing the concept of runoff limit, a zone with tide level difference (hammed tide level) compared when there is an annual maximum runoff discharge with no runoff discharge in Datong is presented. Based on a 1-d hydraulic numerical model, water level boundary conditions in Xuliujing are acquired for 2-d tide current numerical model. Furtherly, 2-d model is verified by the hydrologic data observed in flood season. The results show the runoff limit is mostly limited within west of 123 degrees E, and there is a northeast expanding trend of the outer contour of runoff limit. Moreover, contributed to low flow diversion ratio of north branch, hammed tide level of tide wave in north branch is slightly influenced by runoff compared with south branch.