Residence time of the Danshuei River estuary, Taiwan
Residence time of the Danshuei River estuary, Taiwan
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DOI：
10.1016/j.ecss.2004.01.013
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发表时间：
2004-07
影响因子：
2.8
通讯作者：
Chi-Fang Wang;M. Hsu;A. Kuo
中科院分区：
文献类型：
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作者：
Chi-Fang Wang;M. Hsu;A. Kuo
在本研究中，河口的停留时间定义为最初存在的水包在系统中停留的平均时间，然后被冲走。采用横向积分二维水动力富营养化模型（HEM-2D），通过一系列数值实验计算了丹水河的停留时间。结果表明，在平均河流量至零河流量条件下，停留时间约为1 ~ 2天，与大多数生物地球化学过程的时间尺度相比，停留时间很短。开发了一种程序，以量化潮汐、河流排放和密度诱导循环这三种主要物理传输机制中每一种对冲刷的个人贡献。结果表明，在一般情况下，潮汐冲淤对丹水河河口冲淤的影响最大，密度诱导环流的影响不大。当河流流量低于其长期平均值时，潮汐输运贡献了50%以上的冲刷。并对潮棱柱法、修正潮棱柱法和淡水分馏法在该河口的适用性进行了探讨。相对较短的停留时间可能是导致浮游植物生物量低而营养浓度极高的限制因素之一，并导致很大一部分污染物在河口以外的沿海水域发挥作用。
The residence time of an estuary is defined in this study as the average time the initially existing water parcels reside in the system before they are flushed out. The residence time of the Danshuei River is calculated through a series of numerical experiments using a laterally integrated two-dimensional hydrodynamic eutrophication model (HEM-2D). The results show that the residence time is on the order of 1–2 days under the mean river flow to zero river flow condition, which is very short compared with most time scales of biogeochemical processes. A procedure is developed to quantify individual contribution to flushing by each of the three major physical transport mechanisms: tide, river discharge, and the density induced circulation. The results indicated that, in general conditions, tidal flushing exerts the greatest influence to the flushing of the Danshuei River estuary, while the density induced circulation hardly contributes any. Tidal transport contributes more than 50% of the flushing when river discharge is below its long-term mean. The suitability of applying the tidal prism method, the modified tidal prism methods, and the fraction of freshwater method in this estuary is also investigated. The relatively short residence time is likely to be one of the limiting factors that result in low phytoplankton biomass in spite of extremely high nutrient concentrations, and causes a significant fraction of pollutants to exert their effects in the coastal waters outside the estuary.