The Effects Of Sluice Impounded On Interaction Characteristics And Numerical Simulation Of River-Groundwater

There is a close hydraulic connection between surface water and groundwater.The interaction between them is one of the important links in the natural water cycle,which directly affects the water quantity and quality.In order to make rational use of river resources and effectively regulate river flow,sluice has become one of the most common artificial water conservancy projects.In this study,the Fuli section of Suihe River in Suzhou City,Anhui Province,is selected as the research object.The interaction of water quantity,hydrochemical characteristics and pollutant distribution and transformation of the upper river and groundwater in the reach of sluice are studied,and GMS(ground water modeling)is used as the numerical simulation software System)built a numerical model of groundwater in the study river section,and further explored the influence of river sluice on the interaction characteristics of river and groundwater.The main results of this study are as follows:(1)The water supply rate of the river to the groundwater of the upstream reaches is 15.36%?54.52%,the average supply rate is 0.7077 m3(d·m)-1,the supply rate to the groundwater of the sluice reaches is 43.18%?68.92%,the average supply rate is 0.7710 m3(d·m)-1,the average supply rate to the groundwater of the downstream reaches is-0.0089 m3(d·m)-1,the function of sluice retention makes the replenishment effect of river near the sluice strongest,and the annual interaction of surface groundwater in the lower reaches is only about 1/3 of that in other reaches.(2)From March to November,the hydrochemistry of river water evolves from SO4·Cl-Na type to HCO3·SO4-Na type,and the groundwater near the river evolves from HCO3-Ca type to HCO3-Na type.The hydrochemistry of river water is controlled by the weathering and evaporation of silicate rock,and the hydrochemistry of groundwater near the river is controlled by the weathering of carbonate rock and silicate rock.Because of the sluice action,the interaction between groundwater and river near sluice is strong,and its mixing makes the hydrochemical properties and dominant factors of the groundwater near the river closer to the river water;The water infiltration from the sluice to the upstream reaches is large due to the sluice retaining effect.Groundwater evolves into an oxidizing environment,which improves the solubility of minerals,and TDS increases,which makes the groundwater conducive to the dissolution of K+,Na+,SO42-,and dissolution of CO32-inhibits the occurrence of Ca2+and HCO3-.(3)The sluice has a great influence on the concentration distribution and change trend of the pollutants in the upper river and groundwater in the study area by affecting the infiltration intensity of different river reaches.The change of river water infiltration intensity affects the pH and redox potential of groundwater,and finally affects the occurrence of iron and manganese in the groundwater aquifer of the study area.Due to the sluice,the pollutant input of sluice and upstream reach to the groundwater near the river is the largest in the water storage period of March and April,while it is greatly reduced in the discharge period;in the downstream of sluice,the pollutant output of groundwater to the river is reversed in the discharge period of May to August.(4)Through the simulation analysis of the numerical model,it is found that the retaining effect of the sluice has a significant impact on the groundwater flow field around the river.The groundwater level in the upstream of the sluice rises,the velocity slows down,the groundwater level in the downstream of the sluice rises slowly,the velocity becomes faster,and the infiltration amount of the river increases by 6.30 X 103 m3/d,an increase of 62.44%;simulation analysis of solute transport with the river as the pollution source,due to the role of sluice retention,the maximum concentration of groundwater near the upstream of the sluice and the upstream reaches of the river after pollutant infiltration is 5.85 mg/L,an increase of 0.70 mg/L,and the longest distance of pollutant plume formed by infiltration is 482.8 m,an increase of 108.7 m.However,there is a low concentration area near the downstream of the sluice.