A modelling study of residence time in a macro-tidal estuary
A modelling study of residence time in a macro-tidal estuary
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DOI：
10.1016/j.ecss.2006.08.023
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发表时间：
2007-02
影响因子：
2.8
通讯作者：
D. Yuan;B. Lin;R. Falconer
中科院分区：
文献类型：
--
作者：
D. Yuan;B. Lin;R. Falconer
本文概述了一项数值模拟研究，以预测保守示踪剂在大潮汐河口，即英国默西河口的平均停留时间。采用水动力-弥散综合模型预测了不同潮位和淡水流量条件下的平均停留时间。通过6组实测水动力资料对数值模型进行了验证，模型预测的水位和盐度与现场实测基本吻合。数值模拟结果表明，在默西河口，潮位和河流流量对预测的平均停留时间有显著影响。平均停留时间的值也与剩余潮流的强度密切相关。这是由于在退潮期间，河口上游和河口内很大一部分干涸，因此大量的示踪物质通过深通道输送。淡水流量的增加导致沿主河道的剩余电流强度显著增加，从而减少了平均停留时间。对于较大的河口而言，预测的整体示踪剂在整个河口的停留时间相对较短，在不同的潮位和淡水流量组合下，停留时间从不到1天到4天不等。当潮差和淡水流量均较小时，则局部示踪剂在河口上游的停留时间明显长于河口中下游的预测值。
This paper outlines a numerical modelling study to predict the average residence time of a conservative tracer in a macro-tidal estuary, namely the Mersey Estuary, UK. An integrated hydrodynamic-dispersion model was used to predict the average residence time in the estuary for various tidal level and freshwater discharge conditions. The numerical model was verified against six sets of field measured hydrodynamic data, with the model-predicted water elevations and salinity levels generally agreeing well with the field measurements. The numerical model results show that in the Mersey Estuary both the tidal level and river discharge affect significantly the predicted average residence time. The value of the average residence time is also shown to be closely linked to the intensity of the residual tidal current. This is due to the fact that a large proportion of the Upper and Inner Estuary dries out during low tides, thus a significant amount of the tracer material is transported through the deep channels. An increase in the freshwater discharge causes a considerable increase in the intensity of the residual current along the main channels and thus a reduction in the average residence time. The predicted overall tracer residence time for the whole estuary is relatively short for a relatively large estuary, ranging from less than 1 day to 4 days for various tidal level and freshwater flow combinations. When the tidal range and freshwater discharge are both small, then the local tracer residence time in the upper part of the estuary can be significantly longer than the values predicted for the middle and lower reaches of the estuary.