Application of snowmelt as an active and inexpensive dual isotope groundwater tracer

Binder, Martin; Tritschler, Felix; Burghardt, Diana; Klotzsch, Stephan; Dietrich, Peter; Liedl, Rudolf; Händel, Falk

Application of snowmelt as an active and inexpensive dual isotope groundwater tracer | Verwendung von Schneeschmelze als aktiver und kostengünstiger, zweifacher Isotopen-Grundwassertracer Utilisation de la fonte des neiges comme un traceur actif et peu coûteux des eaux souterraines à double isotope Aplicación de la nieve derretida Como un doble trazador activo y económico de los isótopos en el agua subterránea 融雪水作为活跃及廉价的双重同位素地下水示踪剂的应用 Aplicação de água de degelo como um duplo traçador isotópico de águas subterrâneas ativo e acessível

2019

The use of snowmelt as an inexpensive multi-component tracer solution for active aquifer characterization is investigated, creating a valid alternative to existing artificial water isotope labelling using enriched deuterium oxide (²H₂O) and water-¹⁸O (H₂¹⁸O). The approach directly takes advantage of natural differences between groundwater and precipitation. It is shown, at laboratory-scale and small field-scale, that a direct injection of snowmelt into a porous medium allows for the tracing of water flow and, therefore, for the determination of transport parameters based on the stable isotope signatures (δ²H and δ¹⁸O) and on the sum parameter electrical conductivity (EC). The differences in the isotope signature between the snowmelt and groundwater applied in this study were significant, with ∆(δ²H) = 61.0‰ and ∆(δ¹⁸O) = 8.2‰, while the EC difference was ~0.5 mS/cm. Stable isotope breakthrough was observed to be almost congruent to sodium chloride (laboratory tracer experiment) and to uranine (field-scale push-drift-pull test), clearly supporting the assumption of conservative transport. A crosscheck of the isotope data in δ²H-δ¹⁸O plots revealed no significant biases in the tests. On the other hand, the snowmelt’s EC breakthrough suffered from a slight retardation due to ion exchange and mineral reactions.

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