A numerical modeling study to predict the residence time of a conservative tracer in Oujiang estuary was given in this paper. An integrated hydrodynamic-dispersion model was used to predict the average residence time in the estuary for various tidal range and river discharge conditions. The estuary from Meiao to the river mouth was divided into eight segments. Five representative river discharges and three tidal ranges were selected to give the computational conditions in the numerical simulations. Respectively, the residence time of each segment under different conditions was calculated to investigate the influences of drainage, tidal range and initial condition. The numerical results show that in Oujiang estuary the general regression relationships between the residence time and river discharge are power function,and linear function between the residence time and tidal range. Because of much greater variance of river discharge than tidal range, synthetically, the residence time is mainly affected by drainage. The initial condition affects the average residence time significantly. The average residence time for low tidal level is much greater than that for high tidal level.%利用平面二维数学模型对瓯江下游守恒性污染物质滞留时间的空间变化及其对于径流、潮差、初始排放时刻的响应进行了研究.研究将瓯江梅岙至口门河段分为8个子区域分别进行数值试验.数学模型上、下游边界分别采用径流量和潮位控制.上游径流量选取5个代表性流量,下游选取大、中、小潮及混合潮型进行组合研究滞留时间的基本变化规律.研究认为,瓯江下游河段污染物质滞留时间与径流量呈现极好的幂函数关系,与潮差呈现良好的线性函数关系.由于径流量的变幅远大于潮差的变化,综合而言,滞留时间主要是径流量的函数.污染物的排放时刻对其在河口里的平均停留时间影响巨大,低潮位时刻排放,污染物在河口的平均停留时间大为增加.
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