汾河水库水动力及水质数值模拟

汾河水库是万家寨引黄工程的调节水库和山西省最大的地表水饮用水源地，其上游河段的COD和TN有超标现象，故确定库区污染物的输移扩散规律并提出相应的保护措施对保证水库水质安全至关重要。以工程技术资料、DEM模型、遥感及GPS实测信息为基础，采用GIS技术将汾河水库边界和地形进行数字化处理；通过实测数据进行参数率定与模型验证，确定汾河水库的水动力模型和水质模型；将模型进行耦合联用，以汾河水库的水动力为基础，选取COD和TN进行数值模拟，计算污染物在不同进水浓度时库区污染物超标面积，以库区污染物超标面积百分比来表征水库受污染程度。模拟结果表明:风场是影响水库水动力的主要因素；在静风和主导风力作用下污染物分别沿地形和沿下风向堤岸扩散；污染物超标面积百分比与进水污染物浓度限值呈二次函数关系。

Simulation of hydrodynamics and water quality for Fenhe reservoir

The Fenhe reservoir is the regulating reservoir of the Yellow River diversion project and the biggest surface drinking water sources project of Shanxi Province, and the COD (chemical oxygen demand) and TN (total nitrogen) in the upper reaches of the reservoir are beyond the standards. For ensuring the water quality safety of the reservoir, it’s crucial to determine the law of pollutants’ transport and diffusion and put forward relative protection measures. Based on the engineering data, the DEM model and the meseared information obtained from the remote sensing (RS) and global position system (GPS), the digital processing of the boundary and terrain for Fenhe reservoir by geographic information system (GIS) has been finished; using the measured data to calibrate parameters and verify the model, the hydrodynamic model and a water quality model for Fenhe reservoir have been developed; and on the basis of the hydrodynamics of Fenhe reservoir, we couple the two models, select the characteristic values of COD and TN to numerically simulate and calculate the reservoir’s area where the pollutants are over standards under different pollution concentrations during inflowing. The percentage of the area (Ae) where pollutants are over standards has been taken as a mark of the pollution degrees in the reservoir. It is found that the wind is the main factor influencing the reservoir’s hydrodynamics. Under no-wind conditions, the COD and TN spread along the terrain; under wind conditions, the pollutants spread to the bank along the wind direction. There exists a quadratic function relationship between the Ae and the pollution concentration of influent. The research results will provide an important support for the water quality management of the reservoir. Through the control of the water pollutant concentration, the improvement of the reservoir dynamics and the reduction of the endogenous will be favorable to solving the problems of the water quality in the Fenhe reservoir.