钱塘江是杭州市的重要饮用水源,长期以来咸潮入侵对杭州市饮用水安全构成威胁。采用二维数学模型对闻家堰到仓前河段的水动力和盐度进行了数值模拟,复演了大中小潮情况下水动力和盐度的变化过程,着重分析了地形下切对咸潮入侵程度的影响。结果表明:闸口站断面、七堡站断面平均下切分别为1.64,1.12 m时,可导致闸口站、七堡站大潮潮差分别增加22,9 cm,涨憩后0.5盐度线上移3.7 km,七堡站大潮盐度峰值上升17%。地形下切导致七堡断面凸岸边滩处盐度变化大于深泓线附近,因此,地形下切导致的盐度峰值增大对凸岸处取水口造成的影响较凹岸处更大。

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.