Research On The Vertical Water Volume Interaction Between Surface Water And Groundwater Of The Baiyangdian Wetland

The interaction of surface water and groundwater in wetlands controls the hydrology and ecological environment of wetlands.The biggest problem currently facing is how to describe the interaction process and the estimation of exchange volume.A temperature tracing of a new method as a method,data acquisition has the advantage of low cost and continuous intensive monitoring of the temperature,and can more accurately describe the water flow path,seepage velocity,change trends and influencing factors,presents a new model for the study of ideas and interaction of surface water and groundwater.The hydrodynamic method is based on Darcy's law and has a wide range of applicability as a traditional method.Taking the Baiyangdian Wetland as research object,using real-time monitoring of water level and temperature data to analyze the temporal and spatial distribution of the wetland surface water and groundwater volume interaction,combining hydrodynamic method and temperature tracing method,discussing the factors affecting the wetland water exchange,and calculating the wetland surface water and groundwater exchange volume.Compare the difference and applicability of the calculation results of the hydrodynamic method and the temperature tracing method.The main results of the research are as follows:(1)The sedimentary lithology of the Baiyangdian Wetland is dominated by silty clay and silt,partially mixed with silt and fine sand.Monitoring point Kz longitudinal stronger spatial variability of the horizontal direction,and the vertical permeability coefficient of the sediment is about 4×10^-4?1.87×10^-2m/d.(2)The water level changes of the lake water and groundwater in the Baiyangdian Wetland are basically kept in sync throughout the year.The water level dynamics as a whole presents a seasonal state of"low summer and high winter",and the water level difference is maintained at±0.03m.Due to the influence of outside air temperature,heat conduction and heat convection,the groundwater temperature in summer is in the state of"up high down low",and in winter the groundwater temperature is in the state of"up low down high".The daily change of lake water temperature is the largest.As the following depth increases,the temperature variation gradually decreases and the phase shift increases.(3)Comparing and analyzing the interactive seepage velocity of the monitoring points in the study area during the monitoring period by the hydrodynamic method and the temperature tracing method,the flow exchange directions obtained by the two methods are basically the same.The closer the lake surface sediments to the lake water,the greater the hydraulic connection,the exchange The amount is also in the same order of magnitude.During the monitoring period,the exchange velocity between lake water and groundwater is about 1.4×10^-5m/d?9.86×10^-4m/d,and the groundwater is mainly supplied by surface water.(4)Through the comparative analysis of the two methods,it is found that the hydrodynamic method has a wide range of applicability when accurately measuring the permeability coefficient of the sediment;the temperature tracing method is only suitable for vertical water exchange,and the exchange capacity calculation result will be affected by the lateral temperature interference.The difference is that the amplitude and phase changes of the temperature signal cannot be observed in the deep place of the river bed,which is more suitable for shallow lakes with relatively flat wetland topography.