Abstract:

Saltwater intrusion in Qiantang River has threatened the drinking water safety of Hangzhou city especially when upstream runoff descends. The topography varies fiercely as upstream runoff changes with different seasons and years. To reveal the influence of topographical descending on saltwater intrusion in Qiantang River we built a model to simulate the variation of hydrodynamics and salinity in the reach from Wenjiayan to Cangqian in the presence of spring tide, moderate tide and neap tide, and employed finite volume method to discrete the space. The result shows that the computation values of tidal level and salinity are consistent with the measured data. When the section of Zhakou station descends 1.6m and Qibao station 1.1m in average, the tidal range increases 22cm at Zhakou and 9cm at Qibao. The salinity line (0.5) moves 3.7km upwards and the maximum salinity at Qibao increases 17%. The salinity at the convex bank of Qibao section changes more strongly than that in the adjacent of thalweg, therefore the increment of salinity caused by topographical descending exerts more influence on water intakes at convex bank than those at concave bank.

Key words: topographical descending, saltwater intrusion, tidal level, salinity, Qiantang River, numerical simulation