钱塘江河口盐度数值模拟

NUMERICAL SIMULATION OF SALINITY IN QIANTANG RIVER ESTUARY

强潮河口盐水入侵对饮用水源地危害极大。基于平面二维水动力盐度模型,对典型强潮河口—钱塘江的水动力及盐水入侵过程进行了数值模拟研究。结果表明枯水径流时盐度变化与潮位过程曲线类似,潮差对盐度大小影响显著,径流量的增加将逐渐减小其相似程度。当流量增加到一定程度后,继续增加的一定径流量所产生的抑咸效果减弱,水资源有效利用率降低,此时允许水源地盐度超标并改从蓄淡避咸水库取水可有效节约水资源。盐度平面分布显示,盐水入侵在强潮河口弯道处受涨潮流主流线影响明显,靠近主流线一岸的盐度大于对岸,单从盐水入侵角度考虑,强潮河口弯道段的取水口应设置在远离涨潮流主流线一岸。钱塘江河口盐度数值模拟对于研究减轻盐水入侵对水源地危害的措施具有指导意义。

Saltwater intrusion into macrotidal estuary is harmful to the water quality of the drinking water source. Based on a two-dimensional hydrodynamic salinity model, the progresses of hydrodynamic and saltwater intrusion of typical macrotidal Qiantang River estuary were numerically simulated. It is found that salinity curve has a similar characteristic to the tide level curve at low water runoff, and the tidal range has a great impact on the salinity. However, increase of run-off reduces the similarity gradually. Once the run-off exceeds a certain amount, the impact on saltwater intrusion suppression by run-off increase is reduced, thus the effective rate of water resource utilization is reduced too. Meanwhile, chose a freshwater reservoir instead of Qiantang River as the water source, which could effectively save the water resource. Two-dimensional distribution of salinity shows that rising-tide mainstream line has a great effect on the saltwater intrusion in the bend of a macrotidal estuary. The river bank near the mainstream line has greater salinity than the other parts. Therefore, considering only saltwater intrusion, freshwater intake in river band of a macrotidal estuary should be located away from rising-tide mainstream. The Qiantang River salinity numerical simulation could provide a guide for research on reducing damage by saltwater intrusion to drinking-water source.