感潮河段盐度和缺氧水体时空分布规律研究

感潮河段水体的物质输运规律及其时空分布不仅受径流、潮汐动力的双重影响,还受水闸调度等人类活动的影响.针对水闸调度影响下感潮河段复杂的水动力学及其伴随的物质输运过程,提出一种新的算盘式网格结构,建立了水动力学和物质输送的三维数学模型,考察了在径流、潮汐及水闸调度综合作用下,感潮河段水流密度分层的特点,并对水体中溶解氧和盐度的时空分布规律及其影响因素进行研究.结果发现,数值模拟计算结果与观测值吻合良好,表明所建立的三维数值模型可以很好地预测感潮河段的水流运动和物质输运规律.研究表明,感潮河段的缺氧水体首先出现在盐水楔的前端,在盐-淡水分层强度、盐水停留时间及水闸调度的综合作用下,出现溶解氧浓度持续降低的趋势,并导致缺氧水体范围从河口上游向下游扩展,随水闸的放流缺氧水体被冲刷的现象.

Temporal and spatial distribution of salinity and hypoxia in a tidal river

The mass transport and its temporal and spatial distributions in the tidal rivers are not only influenced by the river flow and tide, but also affected by human activities, such as the operation of barrage gate. Based on the abacus type grid system, a three-dimensional hydrodynamic and mass transport numerical model was constructed with the combined effects of tide, river flow and barrage gate operation. This model was applied to study the feature of density stratification, the temporal and spatial distribution of salinity and dissolved oxygen concentration as well as impact factors in a tidal river. The result of computing results agree well with the observed data, indicating that the three-dimensional model has the capability to simulate the hydrodynamics and mass transport in the tidal river. It is found that the hypoxic water body took place initially at the front of the salt wedge. Under the comprehensive influences of salinity stratification strength, residence time of sea water and the barrage gate operation, the trend of a continuously decreasing dissolved oxygen concentration began to arise, which was followed by the extention of hypoxic water body from upstream to downstream of the estuary and subsequently the flush of hypoxic water body caused by the open barrage gate.