Response Characteristics of Horizontal Salinity Front to Runoff in the Yangtze River Estuary

Abstract:

Based on the monthly average discharge calculated from measured runoff from 1950 to 2018 at the Datong Station in the Yangtze River Estuary， the two-dimensional hydrodynamic and salinity transport model was established by MIKE21 to investigate the effect of runoff change on the position and intensity of horizontal salinity fronts in the four branches of the Yangtze River Estuary after the Three Gorges Project was completed. The numerical results show that： the annual average salinity increases in the mouth of the Yangtze River Estuary and the increase is the most obvious in the South Passage. Except the North Channel， all salinity fronts have a double frontal structure. There is a linear relationship between the position of the salinity front and the runoff， and the change of position at the first front is more obvious than that at the second front. The relationship between the intensity of each front and the runoff is a quadratic function. The coefficient of the quadratic term is positive at the first front and negative at the second front.