Hydrogen and oxygen isotope based transformation studies of surface water and groundwater in plains lakes and swamps
The interconversion between surface water and groundwater and the quantification of groundwater re-charge are important elements in the study of lake water cycle.In this paper,we collected lake water and groundw-ater samples from Yuandang Lake,tested their stable isotope compositions of hydrogen and oxygen and hydrochemi-cal compositions,analyzed their hydrochemical types using Piper's trilinear diagrams,and obtained the groundwa-ter flow fields of Yuandang Lake during the dry season(December 2022)and the rainy season(June 2023)from the measured groundwater in the boreholes,and analyzed the transformation relationship between surface water and groundwater qualitatively with the combination of the electrical conductivity(EC)and total dissolved solids(TDS),and quantified the amount of recharge from the isotope water balance equations.Qualitatively analyzed the transfor-mation relationship between surface water-groundwater,and quantitatively evaluated the amount of transformation between lake water,groundwater,river water and precipitation by combining isotopic water balance equations and linear end-element mixing models.The results showed that the hydrochemistry types of lake water and groundwater in the study area were both of the HCO3-·SO42-·Ca2+·Na+·Mg2+ type,and the lake water was recharged by groundwater in both the dry and rainy seasons,and linear regression equations were derived for the stable isotopes of lake water for hydrogen and oxygen in the dry and rainy seasons,with smaller slopes in the rainy season indica-ting that evaporation was more intense.The lake is mainly recharged by the inlet river water,shallow groundwater and precipitation,whose three recharge ratios are 59%,26%and 15%in the dry season and 23%,39%and 38%in the rainy season,respectively.The results of this paper provide a scientific evidence for the rational devel-opment and protection of the Yuandang Lake area and the Taihu Lake basin.
plains and lakesYuandang Lakehydrogen and oxygen isotopesHydrochemical characterizationisotope water balance modellinglinear end-element hybrid modelling