生态清淤对于桥水库水质影响的数值模拟

Numerical simulation of the effects of the ecological dredging on water quality in Yuqiao Reservoir

以天津于桥水库为例,建立了考虑沉积物-水界面物质交换的二维水动力和营养物质输移模型,基于率定的参数模拟了不同水质背景条件下,水库库周清淤和全库清淤两种方案对水库中的氮、磷营养盐时空分布的影响。结果表明:模型能够可靠地模拟水库底泥氮、磷营养盐的动态释放及其与外界污染输入共同作用下水库的氮、磷营养盐的含量;底泥是于桥水库水体营养盐的重要来源,底泥清除后水库氮、磷营养盐含量均有所下降,但是不同方案的清淤效果存在差异。库周清淤对沿岸带的浅水区水体氮、磷有很好的改善作用,但对库区的整体改善效果不佳(<2%);而全库清淤后,整个库区水体的氮、磷含量均大幅下降(26%~48%),治理效果相对明显。

Yuqiao Reservoir in Tianjin City was taken as an example in this paper, a two-dimensional hydrodynamic and nutrient transport model considering substance exchange across the sediment-water interface was developed. The effects of two different scopes of dredging on the temporal and spatial distribution of nitrogen and phosphorus nutrients in the reservoir under different water quality background were simulated based on calibrated parameters. The results demonstrated that: the established model could reliably simulate the dynamic release of nitrogen and phosphorus nutrient from lake sediment and its content under the combined influence from sediment release and external pollutant input;sediment was an important source of nutrients in Yuqiao Reservoir. The content of nitrogen and phosphorus nutrient in the reservoir would decreased after dredging, but different dredging schemes varied markedly. Dredging around the reservoir contributed much to water quality of shallow coastal waters but had little effect (<2%) on the whole reservoir. Dredging the whole reservoir resulted in a significant decrease (26%~48%) of nitrogen and phosphorus nutrients in the reservoir which showed a relatively obvious improvement on water quality.