农村沟-塘系统水环境过程与格局优化研究——以风岭水库小流域为例

Rural ditch-pond wetland existed as small water conservancy projects in China for thousands of years, which play an important role in maintaining the process and function of water environment. There is increasing awareness that solutions to agricultural non-point source pollution and resulting impacts on downstream water bodies may require a watershed approach to management. The adjustment of land use structure will be carry out under the policy of industrial agriculture, which is the moment to using ditch-pond system to solve the problem of water environment. Reasonable structure of ditch-pond system that may be emulated in developed watersheds to enhance the efficacy of peak-flow attenuation and pollutant removal. This study will choose Fengling watershed as the study area, wherein the ditch-pond system have orderly management and fully ecological service function. This application describes use of simulation modeling to explore the relationship between ditch-pond system patterns and water environment in the watershed scale. Firstly, dynamic systems model and location weighted landscape contrast index were developed to modeling the process of water environment in pond. Secondly, based on the model above and graph theory, landscape network model will be developed in watershed. This model will simulate watershed hydrology, suspended sediment transport and nutrients removal and transformation. Finally, landscape patterns of ditch-pond system can be optimized in terms of both area and numbers of ponds and network characteristics based on the model for purposes of water conservation and agriculture sustainability. The study attempts to explore structure-process of ditch-pond system in landscape scale, which oriented new methodology for ditch-pond system. And the methods and results will be made to provide scientific guidance for regional agriculture planning and land use.

农村沟-塘湿地作为我国存在几千年的小水利工程，在维持水环境过程与功能方面发挥巨大作用。目前，在国家规模化农业政策的背景下，农村沟-塘湿地将面临被填平的威胁。为了深入认识沟-塘湿地在控制雨洪风险与面源污染方面的作用，本研究拟选择江苏省高-宝-邵伯湖区的风岭水库小流域，将沟-塘湿地作为一个系统，探究其水环境过程与格局之间的关系。研究将以单塘湿地水环境功能为基础，利用系统动力学模型分析单塘水环境变化过程；在此基础上从沟-塘网络系统角度，通过构建基于图论的景观网络水环境过程模型，揭示沟-塘网络格局与水文、水质之间的维持关系；并进一步对不同沟-塘网络情景下的水环境过程进行模拟，提出农村沟-塘系统格局优化的最佳方案，以期达到利用有限沟-塘湿地提高水资源利用率、控制农业营养盐输出的目的。因此，本研究的湿地系统认知对深化景观格局与过程研究具有重要理论价值；同时，能够为农村流域水环境保护和利用提供科学依据。

沟-塘系统在农业景观中起着重要的生态作用。在降雨过程中能够截留地表径流及面源污染物，在灌溉需水期又能为农田提供水资源及其所截留的营养物质。因此，在土地集约利用的背景下，合理布局沟塘系统显得尤为重要。本研究通过流域水文模拟和水质监测数据，分析沟-塘系统在流域尺度水文调节空间差异、营养物截留特征、水资源供需平衡空间异质性，在此基础上提出流域沟塘-系统优化方案。研究结果表明：1）区内水塘有615个，总面积达1.75km²，占整个研究区10.11%；2）沟-塘系统对农业面源污染的截留过程在不同作物种植期内差异显著。稻季降雨前水塘的水质比降雨后差，而麦季降雨前水塘的水质要优于降雨后；3）空间上隔离的水塘在水位变化上具有一致性，说明水塘与水塘之间存在水文连通性；4）流域水塘的水文调节量为1.3×106m3/年，水源涵养量为36.47×106m3/年，区内水稻需水总量为40.58×105m3/年。5）研究区内水塘水资源供给短缺的村组共有60个，水资源富余的村组有33个。