Visualization Experimental Study On The Interaction Between Surface Water And Groundwater In Wetland

Wetland is a long-standing natural ecosystem with abundant water resources.Wetland hydrological cycle is an important link of energy,material and information transmission between surface water and groundwater in wetland.Water exchange and water quality evolution are key factors to maintain the health and stability of wetland ecosystem.Due to the complex stratum structure of the wetland,various forms of surface runoff such as open channel flow and sheet flow coexist with the underground water flow in sponge layer,forming a unique law of runoff generation,confluence and water flow movement,which leads to the complicated water circulation process between surface water and groundwater,making the traditional field test,indoor model test and numerical simulation unable to accurately reflect the interaction between surface water and groundwater in the wetland.In this paper,based on the principle of transparent soil,a visual model of wetland structure is constructed,and the internal flow field of wetland under different experimental conditions is obtained by particle image velocimetry(PIV).Through digital image processing technology,the flow characteristics of water flow in wetland are revealed.The main research contents and achievements are as follows:(1)Collect the research data of scholars on the application of transparent soil,and summarize the existing research results,and finally select the transparent soil material suitable for simulating wetlands.The solid particle material is hydrogel particles,and the pore fluid matching its refractive index is distilled water.The saturated transparent soil is prepared according to the mass ratio of 1:200,and samples are taken for penetration test,direct shear test and consolidation test.(2)Using transparent soil to build a visual model of wetland structure,PIV technology is used to record the images of water movement law,velocity field change and siltation in the process of changing rainfall and river position,and digital image processing technology is used to process and analyze the images.The results show that surface water is mainly used to replenish groundwater in the wet season.Rainfall is the main factor affecting the groundwater recharge system by surface water in wetland.With the increase of rainfall(the position of the river remains unchanged),the greater the infiltration rate of water inflow,the shorter the time for surface water recharge to the groundwater system.The secondary factor affect that groundwater recharge system by surface water in wetland is the location of the riv.When the river location is different(the rainfall is the same),the infiltration rate of water in the river area is high than that in other areas of wetland,and the maximum rate is in the middle area of the river,where the water is replenished to the groundwater system first.In the process of groundwater recharge from wetland surface water,siltation will occur.Changing the river position will affect the location of siltation area,and the rainfall will affect the area of siltation area.The greater the rainfall,the smaller the siltation area will be.(3)By changing groundwater pressure,the process of groundwater recharge to surface water is analyzed.The results show that groundwater recharge to surface water is the main method in low water period,the infiltration rate of groundwater recharge increases in turn,the area of silting area becomes smaller,and the distance of groundwater recharge increases in turn in the same time,the groundwater recharge distance under 0.4 MPa is 1.3 times of that under 0.2 MPa,and the groundwater recharge distance under 0.6 MPa is 1.7 times of that under 0.2 MPa.