Fractal study on salinity distribution in the North Branch of Yangtze Estuary

摘要

In this paper, salinity characteristics in North Branch of Yangtze Estuary is studied based on Fractal Theory by analyzing the observed saline data. The inner rules of salt water and fresh water mixing system can be expressed by fractal characteristic values (fractal dimension D and fractal proportionality constant A). Larger fractal dimension D means more homogeneous saline vertical distribution and salt-fresh mixing degree is higher. Fractal proportionality constant A and salinity intrusion intensity have positive correlation. The following conclusions can be drawn. The salt-fresh water mixing degree and salinity intrusion intensity decrease from outside to inside in North Branch of Yangtze Estuary. The curve graph of daily salinity is similar with the tidal level. The maximum of salinity occurs near tidal flood and the minimum occurs near the tidal ebb. The mixture degree during the spring tide is larger than that during the neap tide. The salinity outside the estuary doesn't change much during one spring-neap tide cycle. The saltwater intrusion variation during spring-neap tide cycle is increasingly obvious from outside to inside in North Branch of Yangtze River.