Surface Water And Groundwater Exchange Occurring In Riverside Wetland Impacted By Water Sediment Regulation Scheme Via The Xiaolangdi Reservoir

The interaction between groundwater and surface water is a key aspect in the study of hydrological processes in wetlands.This paper takes the Yellow River Wuzhi wetland downstream of Xiaolangdi dam as the research object,and uses water chemistry and stable isotope tracing techniques to study the water chemistry characteristics and recharge sources of the water bodies in the riverine wetland downstream of the dam under the influence of reservoir water and sand regulation,to reveal the relationship between groundwater and surface water transformation and its mechanism,and to provide scientific basis for the management and sustainable use of water resources,protection of wetland ecosystems and water pollution prevention and control in the middle and lower reaches of the Yellow River.The following research results were obtained in this paper.（1）The cations of the water bodies in the study area are mainly Na⁺,Ca²⁺and Mg²⁺,and the anions are mainly HCO₃^-and SO₄^2-.the water chemistry types of river water are HCO₃·SO₄-Ca·Mg,HCO₃-Na·Mg·Ca and HCO₃-Ca·Mg·Na,and the water chemistry types of groundwater are mainly HCO₃-Ca·Mg·Na,HCO₃-Ca·Mg and HCO₃-Na·Mg.（2）From March to August 2021,the river water level in the study area is higher than the groundwater,and the recharge and discharge relationship during this period is that the river water recharges the groundwater,and the recharge effect is enhanced during the water and sand transfer.from September 2021 to February 2022,the groundwater level in the study area is higher than the river water,and the recharge and discharge relationship during this period is that the groundwater recharges the river water.（3）Both river water and groundwater in the study area are recharged by atmospheric precipitation,and river water is subject to stronger evaporation than groundwater.There are some differences in the isotopic distribution of water bodies in the study area,and the relationship between groundwater and river water recharge is weaker from March to June2021;the hydrogen and oxygen isotopic composition of river water is gradually enriched during the water-sand regulation period,and some groundwater isotopic data points are between the river water isotopic points and the local atmospheric precipitation line,indicating that groundwater is jointly influenced by river water and precipitation recharge;groundwater isotopes are more negative than river water from September 2021 to February 2022,and river water is jointly recharged by groundwater and atmospheric precipitation.（4）UsingδD andδ¹⁸O as tracers,the contribution of river water to shallow groundwater in the study area from March to June 2021 is 90.8%and the contribution of atmospheric precipitation to shallow groundwater is 9.2%using the end element mixing model;from June to July 2021（water and sand transfer period）the contribution of river water to shallow groundwater in the study area is 89.97%and the contribution of atmospheric precipitation to shallow groundwater The contribution rate of groundwater to river water in the study area from September 2021 to February 2022 is 11.12%,and the contribution rate of atmospheric precipitation to river water is 88.88%.