基于河湖连通性的升金湖湿地地表水-地下水转换机制研究

Shengjin Lake wetland is typical Yangtze-connected lake wetlands in Anhui province, Due to the complex interactions between rivers and lake, it provide a wide habitats to variety of biological. The original water cycle model was broken by water conservancy construction. Therefore, it is a serious problem to analysis the conversion mechanism between groundwater and surface water based on the connection of rivers and lakes. In this project, environmental isotopes and water chemistry as the main means, based on field sampling, to tested and analyzed spatio-temporal variations that the chemical element and environmental isotopes (δD, δ18O and 3H) in different water bodies(river, lake, wetland and groundwater). The relationship between recharge and discharge of the river, lakes and wetlands was study by isotope mixing model, and then to reveal hydrological cycle and the mechanism of surface water and groundwater. By comparing of chemical characteristic and isotopic values in the both sides of Huangpen gate, to analysis the connection of the Yangtze River, lakes and wetlands on the quality and quantity. By studying the exchange relationship of quantity and quality between groundwater and surface water, provide a theoretical basis for river and lake water connectivity strategy implementation, improve water resources overall configuration, strengthen the ecological environment quality and flood -control.

安徽升金湖湿地是典型的通江湖泊湿地，复杂的江湖关系创造了丰富多彩的生物栖息地及生物多样性。修建控水闸（黄湓闸）改变了河湖水系原有的连通状况，河、湖和湿地不同水体之间水力联系是评价河湖水系连通性的重要依据，定量研究河湖交汇区地表水-地下水之间的转换机制是亟需解决的问题之一。项目拟以环境同位素和水化学方法为主要手段，采集河湖交汇区不同区段、不同水体水样，测试其环境同位素(δD、δ18O 和3H) 和化学元素成分；以分析河湖水系水质和水量的连通性为主要目的，①分析化学元素主成分和时空分布特征,评价控水闸对河湖水质连通性的影响；②分析环境同位素的时空分布特征，并结合同位素混合模型，探讨不同水体之间的补排关系，揭示地表水和地下水的转换机制及其的水文循环特征；③评价长江、湖泊和湿地水体质和量上的连通性。该项目拟为河湖水系连通战略实施，提高水资源统筹配置能力，加强生态环境质量和防洪保安能力提供理论基础。

围绕人工修筑控水闸坝对河湖水系连通性影响这一研究热点，本项目选择了升金湖河湖交汇区作为研究区，通过收集不同水位站逐日水位数据，采集长江、湖泊、闸控两侧河道、地下水等不同水体在不同季节的水样，测试其环境同位素(δD、δ18O 、δ15N-NO3-和δ18O-NO3-) 和化学离子（TP、TN、NO3-、NH4+和NO2-等）含量。研究结果表明，在现有闸坝控水条件下，枯水期升金湖面积有所增大，最大增幅可达30.98 km2，而在高水位时升金湖面积有所减小，最大减幅约10 km2。通过对比分析发现闸控两侧水体TP、TN等化学离子含量以及δD、δ18O值均存在明显差异，并和控水闸运作方式有很大关系，并且通过同位素径流分割模型，得出地表、地下水补排关系受河湖水位变化的影响。此外，项目还通过分析河湖交汇区地表水、地下水δ18O、δD值的空间变化，结合同位素径流分割模型，得出长江、湖泊对河湖过渡带地下水的补给范围和补给比率，探讨了河湖交汇区地表、地下水体之间的转换机理。