水文情势变化下汉江中下游流域湿地系统功能结构及生态响应机制

Han River is the longest tributary of the Yangtze River. The Middle Route of South-to-north Water Diversion Project is a significant strategic project to implement the optimal allocation of water resources in China and to solve the water shortage problem in the north. It also improves the flood-control standard of the middle and lower of Han River and ensures regional water security. Under the combined effects of human and nature, the dramatic variation of hydrological processes in the middle and lower of Han River will inevitably lead to changes in wetland structure, processes and functions. This provides conditions to study the impacts of hydrological environmental change on wetland ecosystem evolution and provides experimental conditions for the study of river wetland succession. This project focuses on the middle and lower of Han River Basin from Danjiangkou Reservoir Dam. The aim is to analyze the spatial-temporal distribution and variation trends of major hydrological factors synthetically under the influence of hydraulic engineering, such as the Middle Route of South-to-north Water Diversion Project, the Water Diversion Project from Yangtze River to Han River, and the Midstream Cascade Drainage Engineering. Then it is to inquire the influence of man-made, natural succession and regional land-use change on the evolution of the middle and lower of Han River wetlands and reveal the driving factors of river and lake wetland evolution. The project is also to reveal the relationship between wetland processes and ecological response based on the watershed spatial properties, to propose programs of wetland ecological protection and watershed water resource adaptive management based on hydrology-ecologic response mechanism and to provide a theoretical basis for eco-hydrological regulation of hydraulic engineering.

汉江是长江最长的支流，南水北调中线工程是实施我国水资源优化配置，解决北方缺水问题的重大战略工程；同时也提高了汉江中下游的防洪标准，可保障区域水安全。在人为与自然双重影响下汉江中下游河段形成的剧烈水文变化过程，必然会引起湿地结构、过程和功能的变化，为研究水文环境变化对湿地生态系统的演化影响研究提供了条件，为研究河流湿地演替过程提供实验条件。本项目以丹江口水库坝下的汉江中下游流域为研究区域，综合分析中线调水工程和“引江济汉”和中游梯级渠化工程等水利工程影响下的汉江中下游主要水文要素时空分布规律及变化趋势，探讨人为调控与自然演替及区域土地利用方式变化等对汉江中下游湿地演化的影响作用，揭示河湖湿地演变的驱动因子；揭示基于流域空间属性的汉江中下游湿地过程与生态响应关系，提出基于水文-生态响应机制的汉江中下游湿地生态保护和流域水资源适应性管理方案，为水利工程的生态水文调控提供理论依据。

汉江流域是南水北调中线工程的水源地，战略地位显著。随着梯级枢纽水利工程修建，汉江中下游流域水文过程发生了剧烈变化，其变化必然会引起湿地结构、过程和功能变化。本项目以汉江中下游为研究区域，分析中线调水、梯级渠化等多重水利工程影响下汉江中下游水文情势变化，探讨流域湿地生态对水文情势变化的响应机制，并综合分析区域土地利用变化对汉江中下游湿地演化影响，揭示湿地生态过程与水文响应关系，提出基于水文-生态响应机制的汉江中下游湿地保护和流域水资源适应性调控方案，为流域生态水文调控、水资源管理提供理论依据。.主要研究成果：（1）研究了典型河段湿地结构特征及景观格局变化，分析了水文要素与景观格局指数之间的关系，研究表明汉江中游湿地景观指数对枯水期水文要素的响应更敏感；（2）开展了汉江中下游重点河段湿地生物多样性研究，探讨了湿地植物分布及多样性演替影响，结果表明汉江中下游干流湿地植被随高程不同呈现不同的植被结构组成；（3）研究了多重水利设施对汉江中下游水文情势的影响；运用泥沙鉴别因子法分析了汉江中游水沙关系变化的驱动力。结果表明丹江口水库及梯级水库的修建对水文情势的改变很大；（4）利用小波改进后GEP模型预测了河流流量；建立了汉江中下游河道的一维水动力模型，将流域水文改变、生态需水评估与模型模拟结合起来，寻找一个对中下游河流湿地生态更优的水库出库流量；建立了汉江中游河道的MIKE 21水动力模型，分析了不同水文时长及泥沙公式在人为干扰较大流域的适用性；（5）完成了汉江流域SWAT分布式水文模型的本地化构建，研究了径流对气候及土地利用变化的响应关系。结果表明流域未来降水量变化会对区域水资源变化产生重要影响，洲滩林地和草地面积增加，使径流量呈下降趋势；（6）基于关键时期-区域协同分析针对性制定了汉江流域湿地保护与水资源适应性调控策略。结果表明基于关键时期-区域协同分析能有效提高流域生态流量调控的针对性及环境经济效益。