The effects of river regime changes in the Changjiang Estuary on hydrodynamics and salinity intrusion in the past 60 years Ⅱ. Hydrodynamics

In this paper, with the digitized data of 1950s and 1970s and measured date of 2012, model grids were designed. Considering the effects of runoff, tide and wind stress, a 3D numerical model of Changjiang Estuary was built to simulate and analyze the tide, residual water transport, water flux and split ratio in bifurcations and the effects of river regime changes on them. The changes of the maximum tidal range occurs mainly in the North Branch, the tidal range of middle reaches of the North Branch decreased from 1950s to 1970s, and increased from 1970s to 2012.In 1950s, the residual water transport was greater in the North Channel than in the South Channel,transported toward the upper reaches in the lower reaches of the North Branch and its value was low in the upper reaches of the North Branch. In 1970s, the residual water transport was greater in the South Channel than in the North Channel, transported toward the lower reaches in the upper reaches of the North Branch and its value was low in the lower reaches of the North Branch. In 2012, the residual transport was equivalent in the North Channel and the South Channel,transported toward the upper reaches in the North Branch. The flood, ebb and net water split ratio during spring and neap tide in the North and South Branch, and the North and South Channel in the three times was given and the reason of change was analyzed based on the change of river regime.