苏北平原灌区沟渠网络水系连通性对水环境过程影响机制与调控研究

Ditch networks are complex and the direction of water flow is not defined on Subei Plain. The ditches do not always connect because of human regulation. So, the ecological function of ditch networks does not work well. Overfertilization also causes the water pollution. By considering the connectivity and water movement characteristics of ditches, this project aims to propose hydrological and water quality modeling method that can reflect the characteristics of water movement in this region. The model will prodict water quality when ditch networks connectivity is changed. High resolution remote sensing information, GIS technology and model method can be used in this project. Ditch connectivity will be identified from static and dynamic condition by 2 years field data. Based on module modeling method, ditch network connectivity and water movement identification will be added in the exsiting model. The modified model can be described the characteristics of water flow and route. The water quality model will be established by the result of isotopic tracing technique of non-piont pollution and the method of energy symbol language. Multi-objective scheduling rules will be studied and expressed by considering hydrological and water quality model as constraint condition. This project can provide high-quality routing network input for hdrological modeling in the Subei plain region and improve the precision of modeling. It can also provider theoretical basis of water connectivity project.

苏北平原灌区沟渠网络密集、水流运动复杂、人为调控强烈，导致水系连而不通，通而不畅，沟渠生态功能得不到充分发挥。加之区内过度施肥现象普遍，使得农村沟渠水污染严重。本研究拟从平原区汇流特征、沟渠连通性的表达机制出发，研究能够体现沟渠连通性特征的水文水质过程模型，探索如何通过改变水系连通性来达到提升水环境的目的。研究拟利用高分遥感信息、GIS技术和模型模拟方法，以连续2年野外调查数据为支撑，从静态和动态两方面揭示沟渠网络连通性；利用模块化建模方法，将水流关系识别及沟渠网络连通性嵌入到已有模型中，建立能够体现该区域水流运动特点的汇流网络水文模型；并借助面源污染示踪结果及能量语言方法，构建沟渠网络水质模型；在此基础上，将水文水质模型作为约束条件，建立基于水量水质多目标调度规则。该研究可为平原灌区沟渠网络水环境过程模拟提供更现实的汇流网络输入，提高模型模拟精度，为区域水系连通实践提供理论依据。

平原河网地区地势平坦，河网复杂，水流迂回，容易造成排污不畅，不利于污染物的迁移扩散。本项目选取典型的平原河网区域——苏北灌区作为研究区，研究区内从城市到农村，水质状况逐步变好，水文连通性指标在空间上整体呈逐步增大的趋势；水文连通性对水质综合指数在空间上的解释程度达到了63.74%，解释效果良好，说明水文连通性与水质在空间上存在相互关系，影响水质综合指数较大的水系连通性指标分别为沟渠网络环度与沟渠节点连接比；使用HEC-RAS水动力模型模拟河道内流量值与实测数据吻合度较高，模拟结果较好。基于水文水动力模拟结果进行水质模拟，总氮的模拟值与实测值之间的误差在20%以内，总磷模拟值与实测值之间的误差在30%以内。在此基础上，分析各种水文连通情境下各区域内的水质变化程度，从中选出基于水文连通差异下的水质优化方案，结果发现增大流量及增加沟渠均会改善研究区内水环境质量。研究结果可为区域水质提升可供理论支撑和科学依据。