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  • Publication
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    Natural tracers to quantify seasonal variations of groundwater mixing in a complex alluvial aquifer (Pfynwald, Switzerland)
    (: Int Assoc Hydrological Sciences, 2000)
    Schurch, Marc
    ;
    ;
    Dassargues, Alain
    Dissolved sulphate, oxygen-18, deuterium and tritium have been used to quantify seasonal variations of groundwater mixing in a complex alluvial aquifer in the upper Rhone valley (Pfynwald, Wallis, Switzerland). The concentration of these four natural tracers reflects spatial and seasonal chemical variations of the alluvial Rhone aquifer. Further they represent mixing rates between weakly mineralized infiltrated Rhone River water and SO4-rich water flowing from the south valley side. The delta O-18 composition decreases from -14.03 parts per thousand at the south valley side to -14.85 parts per thousand near the Rhone River and follows the general groundwater flow pattern as well as the observed dissolved sulphate distribution. A positive correlation exists between the delta O-18 values and sulphate concentrations and can be represented by a linear regression. A two-component model has been applied to tritium concentrations to calculate groundwater mixing rates during high and low water-level periods.