基于GSFLOW的镜湖湿地地表水与地下水耦合数值模拟

Numerical simulation of coupling surface water and groundwater based on GSFLOW for the Jinghu Wetland

湿地地表径流包括明渠流和片流等多种形式,且存在海绵状土壤层,其地表水-地下水耦合模拟困难。针对湿地片流和海绵层模拟不准确的问题,以绍兴镜湖国家城市湿地公园为研究对象,考虑湿地多年植物生长沉积形成的独特海绵层,基于GSFLOW模型构建湿地地表水与地下水耦合数值模型,通过二维扩散方程模拟湿地片流、一维圣维南方程模拟湿地明渠流,使用竖管法测量湿地海绵层渗透系数,利用模拟区水文站的监测数据率定模型参数并对模拟结果进行验证,应用校正后模型模拟湿地地表水与地下水的水量交互过程,并对研究区进行水均衡分析。研究结果表明:考虑湿地海绵层的湿地地表水与地下水耦合模型能较为真实地反映湿地水文特性,湿地以地表水补给地下水为主,补给量随降雨量变化。研究建立的湿地地表水与地下水耦合模型合理可靠,对湿地水文分析有良好的应用价值。

Surface runoff in wetland includes various forms such as open channel flow and sheet flow,and wetland exists the spongy soil layer.Therefore,it is difficult to carry out coupling simulation of wetland surface water and groundwater.In view of the shortcomings of the coupling numerical simulation of the current wetland surface water and groundwater,researches are conducted to solve the problem of accurate simulation of wetland sheet flow and sponge layer.The Shaoxing Jinghu National Urban Wetland Park is taken as the research object,and the unique sponge layer formed by the growth and deposition of wetland plants for many years is considered. A coupling numerical model for surface water and groundwater in wetland is constructed based on the GSFLOW model. The wetland sheet flow is simulated by the 2D diffusion equation and the wetland open channel flow is simulated by the 1D Saint Venant equation. The coefficient of permeability of the wetland spongy layer is measured by using the straight standpipes. The model parameters are calibrated and the model simulation results are verified by using the monitoring data of the hydrological station in the simulation area. The calibrated model was used to simulate the interaction process of wetland surface water and groundwater, and the water balance analysis is carried out in the study area. The results show that the coupling model of wetland surface water and groundwater considering the wetland sponge layer can reflect the hydrological characteristics of wetlands more realistically. The groundwater in wetland is mainly recharged from surface water, and the recharge varies with rainfall. The coupling model of wetland surface water and groundwater established in this paper is reasonable and reliable, and is of important application value for wetland hydrological analysis.