Flushing time of the Yangtze estuary by discharge is one of the importantfactors responsible for the transport of pollutants from various sources located along the Yangtzeestuary: Therefore, an objective of the presen...Flushing time of the Yangtze estuary by discharge is one of the importantfactors responsible for the transport of pollutants from various sources located along the Yangtzeestuary: Therefore, an objective of the present stud-y, which analysis flushing time in the case ofdifferent discharge is very helpful to evaluate the water environmental of the Yangtze estuary.Using a dissolved conservative material as a tracer in the water, a three-dimensionadvection-diffusion water exchange numerical model was used to study the flushing time by dischargeand the discharge dominated region of the Yangtze estuary. The initial tracer concentration is setto 0.0 in the numerical domain of the Yangtze estuary, and the concentration value is set to 1. 0 onthe inflow boundary. The tracer flux normal to the solid boundary is set to 0. 0. The flushing timeand the out limit of discharge dominated region can be calculated in terms of the tracerconcentration. Estuarine, Coastal and Ocean Model (ECOM) is used as the hydro-dynamic model. Theresult shows that the flushing time is approximately in inverse proportion to the discharge at theupper stream. The out limit is farther from the upper inflow boundary as discharge increases. Theout limit at the north branch is different from that of the south branch because the discharge intothe north branch is much less than that into the south branch. The data is qualitative similar tothe observed data, which show the three-dimensional advection-diffusion equation can be used toestimate the flushing time and the discharge dominated region of the Yangtze estuary.展开更多
Accurate determination of flushing time is crucial for maintaining sustainable production in fish culture zones （FCZs）, as it represents the physical self-purification capability via tidal exchange with clean water ...Accurate determination of flushing time is crucial for maintaining sustainable production in fish culture zones （FCZs）, as it represents the physical self-purification capability via tidal exchange with clean water in the outer sea. However, owing to the temporal and spatial complexity of the coastal flushing process, existing methods for determining flushing time may not be generally applicable. In this paper, a systematic method for determining the flushing time in FCZs is presented, in which bathymetry, runoff, tidal range and stratification are properly accounted for. We determine the flushing time via numerical tracer experiments, using robust 3D hydrodynamic and mass transport models. For FCZs located in sheltered and land-locked tidal inlets, the system boundary can be naturally defined at the connection with the open sea. For FCZs located in open＇waters, hydrodynamic tracking is first used to assess the extent of tidal excursion and thus delimit the initial boundary between clean water and polluted water. This general method is applied to all designated marine FCZs in Hong Kong for both the dry and wet seasons, including 20 sheltered FCZs （in semi-enclosed waters of Tolo Harbour, Mirs Bay, and Port Shelter） and 6 FCZs in open waters. Our results show that flushing time is the longest in inner Port Shelter （about 40 days in dry season）, and the shortest for the FCZs in open waters （less than one week in dry season）. In addition, the flushing time in dry season is commonly longer than that in wet season： 20%~40% for most well-sheltered FCZs; 2.6-4 times for the others. Our results indicate a positive correlation between the flushing time and distance to open boundary, supporting the view that the flushing time of a FCZ is closely related to its location. This study provides a solid basis for mariculture management such as the determination of carrying capacity of FCZs.展开更多
本文利用高分辨率数值模型,以2001年秋季为例,详细分析了影响坦帕湾水交换的三种因素:潮汐、河流和风。论文共设置了三组实验,驱动力分别为潮汐,潮汐和河流,潮汐、河流和风。模拟结果显示:只有潮汐作用时,由于坦帕湾潮汐较弱,潮程较短,...本文利用高分辨率数值模型,以2001年秋季为例,详细分析了影响坦帕湾水交换的三种因素:潮汐、河流和风。论文共设置了三组实验,驱动力分别为潮汐,潮汐和河流,潮汐、河流和风。模拟结果显示:只有潮汐作用时,由于坦帕湾潮汐较弱,潮程较短,坦帕湾与其临近海域的水交换主要发生在湾口附近;当潮汐和河流共同作用时,由于河流和湾口海水盐度的不同形成了水平密度梯度,在其产生的水平密度梯度力的作用下,坦帕湾形成了表层流向湾外、底层流向湾内的重力环流,从而加强了坦帕湾跟其临近海域的水交换;由湾内指向湾外方向(2001年秋季平均)的风应力加强了流向湾外的表层流,同时水位梯度力发生了反转,变成了由湾口指向湾顶,这加强了流向湾内的底层流,表层流和底层流的加强最终促进了坦帕湾跟其临近海域的水交换;在航道处,水深较深瑞利数较大,该处的重力环流较强,这使得相对于两侧的浅水区,航道处的水交换能力较强。此外,文章还分析了坦帕湾水交换的空间差异,在Old Tampa Bay的西侧和北侧,滞留时间最长,水交换能力最弱。为减少海洋生态灾害发生,今后应重点加强对该地区的生态环境保护。展开更多
A three-dimensional hydrodynamic model with the capability to deal with changing land water boundaries was developed based on ECOMSED in this study. The model was configured to numerically study the water flushing cha...A three-dimensional hydrodynamic model with the capability to deal with changing land water boundaries was developed based on ECOMSED in this study. The model was configured to numerically study the water flushing characteristics of Dahuofang Reservoir in China through the determination of spatially distributed residence times. The model successfully reproduced the intra-annual water level variations, as well as the temporal evolution and spatial distribution of water temperature. Through a series of numerical experiments, it can be concluded that （1） the water flushing of the reservoir is both temporally and spatially variable; and （2） inflows and withdrawals are the decisive factors influencing the water flushing characteristics. Heat fluxes are the controlling factors of the water flushing of a strong stratified reservoir. Wind has the weakest effect, but it still should be considered in determination of reservoir water flushing characteristics.展开更多
文摘Flushing time of the Yangtze estuary by discharge is one of the importantfactors responsible for the transport of pollutants from various sources located along the Yangtzeestuary: Therefore, an objective of the present stud-y, which analysis flushing time in the case ofdifferent discharge is very helpful to evaluate the water environmental of the Yangtze estuary.Using a dissolved conservative material as a tracer in the water, a three-dimensionadvection-diffusion water exchange numerical model was used to study the flushing time by dischargeand the discharge dominated region of the Yangtze estuary. The initial tracer concentration is setto 0.0 in the numerical domain of the Yangtze estuary, and the concentration value is set to 1. 0 onthe inflow boundary. The tracer flux normal to the solid boundary is set to 0. 0. The flushing timeand the out limit of discharge dominated region can be calculated in terms of the tracerconcentration. Estuarine, Coastal and Ocean Model (ECOM) is used as the hydro-dynamic model. Theresult shows that the flushing time is approximately in inverse proportion to the discharge at theupper stream. The out limit is farther from the upper inflow boundary as discharge increases. Theout limit at the north branch is different from that of the south branch because the discharge intothe north branch is much less than that into the south branch. The data is qualitative similar tothe observed data, which show the three-dimensional advection-diffusion equation can be used toestimate the flushing time and the discharge dominated region of the Yangtze estuary.
基金supported by the Hong Kong Jockey Club Charities Trust (Project Waterman)in part by a grant from the University Grants Committee of the Hong Kong Special Administrative Region (HKSAR),China (Project No. AoE/P-04/04) to the Area of Excellence in Marine Environment Research and Innovative Technology (MERIT)+1 种基金The support from the National Science Fund for Distinguished Young Scholars (Grant No. 50925932)the National Natural Science Foundation of China (Grant No.41001348)
文摘Accurate determination of flushing time is crucial for maintaining sustainable production in fish culture zones （FCZs）, as it represents the physical self-purification capability via tidal exchange with clean water in the outer sea. However, owing to the temporal and spatial complexity of the coastal flushing process, existing methods for determining flushing time may not be generally applicable. In this paper, a systematic method for determining the flushing time in FCZs is presented, in which bathymetry, runoff, tidal range and stratification are properly accounted for. We determine the flushing time via numerical tracer experiments, using robust 3D hydrodynamic and mass transport models. For FCZs located in sheltered and land-locked tidal inlets, the system boundary can be naturally defined at the connection with the open sea. For FCZs located in open＇waters, hydrodynamic tracking is first used to assess the extent of tidal excursion and thus delimit the initial boundary between clean water and polluted water. This general method is applied to all designated marine FCZs in Hong Kong for both the dry and wet seasons, including 20 sheltered FCZs （in semi-enclosed waters of Tolo Harbour, Mirs Bay, and Port Shelter） and 6 FCZs in open waters. Our results show that flushing time is the longest in inner Port Shelter （about 40 days in dry season）, and the shortest for the FCZs in open waters （less than one week in dry season）. In addition, the flushing time in dry season is commonly longer than that in wet season： 20%~40% for most well-sheltered FCZs; 2.6-4 times for the others. Our results indicate a positive correlation between the flushing time and distance to open boundary, supporting the view that the flushing time of a FCZ is closely related to its location. This study provides a solid basis for mariculture management such as the determination of carrying capacity of FCZs.
文摘本文利用高分辨率数值模型,以2001年秋季为例,详细分析了影响坦帕湾水交换的三种因素:潮汐、河流和风。论文共设置了三组实验,驱动力分别为潮汐,潮汐和河流,潮汐、河流和风。模拟结果显示:只有潮汐作用时,由于坦帕湾潮汐较弱,潮程较短,坦帕湾与其临近海域的水交换主要发生在湾口附近;当潮汐和河流共同作用时,由于河流和湾口海水盐度的不同形成了水平密度梯度,在其产生的水平密度梯度力的作用下,坦帕湾形成了表层流向湾外、底层流向湾内的重力环流,从而加强了坦帕湾跟其临近海域的水交换;由湾内指向湾外方向(2001年秋季平均)的风应力加强了流向湾外的表层流,同时水位梯度力发生了反转,变成了由湾口指向湾顶,这加强了流向湾内的底层流,表层流和底层流的加强最终促进了坦帕湾跟其临近海域的水交换;在航道处,水深较深瑞利数较大,该处的重力环流较强,这使得相对于两侧的浅水区,航道处的水交换能力较强。此外,文章还分析了坦帕湾水交换的空间差异,在Old Tampa Bay的西侧和北侧,滞留时间最长,水交换能力最弱。为减少海洋生态灾害发生,今后应重点加强对该地区的生态环境保护。
文摘A three-dimensional hydrodynamic model with the capability to deal with changing land water boundaries was developed based on ECOMSED in this study. The model was configured to numerically study the water flushing characteristics of Dahuofang Reservoir in China through the determination of spatially distributed residence times. The model successfully reproduced the intra-annual water level variations, as well as the temporal evolution and spatial distribution of water temperature. Through a series of numerical experiments, it can be concluded that （1） the water flushing of the reservoir is both temporally and spatially variable; and （2） inflows and withdrawals are the decisive factors influencing the water flushing characteristics. Heat fluxes are the controlling factors of the water flushing of a strong stratified reservoir. Wind has the weakest effect, but it still should be considered in determination of reservoir water flushing characteristics.
