平原河网区水系连通改善水环境效果评估

河流水系是城市重要的资源和环境载体,经济社会快速发展的同时,城市发展与水环境保护之间的矛盾日益突出,尤其是平原河网地区,由于地貌条件制约,城市河道水环境改善难度大。城市水系的可持续发展将直接关系到城市乃至整个社会的健康发展,贯彻现代水系治理思路,通过水系连通促进水环境的改善成为城市治水的重要一环。论文选择常熟市城区作为研究区,以引水实验与水量水质模型作为技术支撑,找出水系连通改善水环境的关键问题,基于此整合水系结构连通性与水力连通性概念,提出水系连通度评价方法。引水实验成果表明,骨干河道水流交换通畅,重要河道水质在引水实验中改善率平均在20%~30%,但主城区河道存在连通受阻。河道连通性的提升与水利工程的合理调度对于以水环境改善为目标的连通体系有着重要影响,以本文两个连通情景为例,河道的整治使得结构连通性增强,河道水质平均改善率提升至30%~50%。从连通性指数的变化来看,结构性连通的提升提高了调水效率,极大地促进了水力连通与水质改善。论文建立的水系连通改善水环境的方法体系能够为水系连通决策提供理论依据,对我国城市水系连通实践提供参考。

Evaluation of water environment improvement by interconnected river network in plain area

River water system is an important resource and environmental carrier of the city. The contradiction between urban development and water environment protection is becoming more and more prominent in recent years, especially in the plain river network area. Due to geographical constraints, the improvement of urban river water environment is challenging. The sustainable development of urban water system will be directly related to the healthy development of cities and the whole society. Therefore implement modern water system management theory and promote water environment improvement through the interconnected river system has become an important step of urban water management. In this paper, the urban area of Changshu city is selected as the research area. The water transfer experiment and the hydraulic model are applied as technical support to formulate river interconnected schemes for the sake of water environment enhancement. Based on the concept of structural connectivity and functional connectivity, the river network connectivity assessment method is proposed. In the water transfer experiment, flow exchange in major rivers is satisfied and water quality of indexes is increased 20%-30% in average. Yet the river connectivity in the central downtown is limited which leads to less flow access. The improvement of river channel connectivity and the reasonable dispatching of water conservancy project have important influence on the connectivity system. Taking the scenario simulations in the paper as an example,channel regulation projects increase river connectivity and give rise to water quality about 30%-50%. The change of connectivity index also prove that structural connectivity greatly enhances water transfer efficiency, and promotes better flow distribution and water environment. The establishing methodology of interconnected water system to improve water environment can provide theoretical basis for water system connectivity decision, and provide reference for urban water system connectivity in China.