岸线变化和海平面抬升对珠江河口水体交换的影响

Influence of coastline change and sea-level rise on water exchange in the Pearl River Estuary

水体交换能力是评价河口水域自净能力的一个指标。为研究岸线变化下珠江河口水体交换能力的变化情况以及海平面抬升对其的影响,建立珠江河口二维水动力-保守物质运输模型,并将模型模拟的水位、流速、流向结果与实测数据进行对比。运用欧拉法,分别计算洪枯季、高低潮位下不同年代岸线变化和海平面抬升不同高度时珠江河口水体滞留时间的变化情况。结果表明:岸线围垦对珠江河口各水域水体交换的影响不尽相同,如从20世纪70年代—2010年,伶仃洋水域的平均水体滞留时间先保持几乎不变后略微减小,而黄茅海和磨刀门水域则因状况而异;海平面抬升不利于水体交换,珠江各水域平均水体滞留时间随海平面抬升而增长,且枯季增加的时间大于洪季。

Water exchangeability is an indicator for evaluating the self-purification ability of estuary.To study the influence of shoreline changes and sea level rise on water exchange in the Pearl River Estuary,we establish a two-dimensional hydrodynamic-conservative mass transport model,compare the results of water level and flow direction simulated by the model with the measured data,and use the Euler method to calculate the water residence time variation of the Pearl River Estuary due to coastline changes and sea-level rise under the condition of wet and dry seasons and high and low tides.The results show that the impact of shoreline changes on water exchange in the Pearl River Estuary is different,for example from the 1970 s to 2010,the average water residence time of the Lingding Bay first remains almost unchanged and then decreases slightly,while the water average water residence time of the Huangmao Bay and Modao Bay vary depending on the situation.Sea level rise is not conducive to water exchange,the water residence time increases with the rise of sea level,and the time increases in the dry season is longer than that in the wet season.