NUMERICAL STUDY ON THE SALTWATER SPILLING OVER FROM THE NORTH BRANCH IN THE CHANGJIANG ESTUARY

摘要

The quantitative relationship of runoff and tidal range to the saltwater spilling over (SSO) from the North Branch as a particular saltwater intrusion phenomena in the Changjiang Estuary is obtained by using the 3D numerical model ECOM-si for the first time. The diurnal and semimonthly net transectional water mass flux (NTWF) at the upper reaches of the North Branch is numerically calculated and analyzed for the intensity of SSO. The diurnal NTWF is obtained in the form of 533.l×exp(0.361×Isso)-533.1 (Isso≥0) and 226.0×Isso (Isso ＜0), in which Isso (index of SSO) is defined as TR -1.58 × exp(0.2457 ×RF/10000), where TR is the tidal range with the unit of meter at the Qinglong Harbor, and RF is the runoff with the unit of m3s-l. The Isso has the same sign as the diurnal NTWF. The semimonthly NTWF is obtained in the form of 701.89×ln(-RF/10000 + 6.2)-553.54. It decreases with the increasing of runoff and declines to zero when the runoff reaches 40000 m3s-l. So the diurnal and semimonthly NTWF can be given by using these formulae and the observed data derived from the Datong Station (runoff) and Qinglong Harbor Station (tidal range).