Articles | Volume 30, issue 6
https://doi.org/10.5194/hess-30-1523-2026
https://doi.org/10.5194/hess-30-1523-2026
Research article
 | 
25 Mar 2026
Research article |  | 25 Mar 2026

Different tracer, different bias: using radon to reveal flow paths beyond the Window of Detection

Johanna Bacher, Julian Klaus, Adam S. Ward, Jasmine Krause, Catalina Segura, and Clarissa Glaser

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Cited articles

Atkinson, A. P., Cartwright, I., Gilfedder, B. S., Hofmann, H., Unland, N. P., Cendón, D. I., and Chisari, R.: A multi-tracer approach to quantifying groundwater inflows to an upland river; assessing the influence of variable groundwater chemistry, Hydrol. Process., 29, 1–12, https://doi.org/10.1002/hyp.10122, 2015. 
Bacher, J., Klaus, J., and Glaser, C.: OTIS-R, GitHub [code and data set], https://github.com/mortimerluka/OTIS-R (last access: 12 February 2026), 2025. 
Becker, P. S., Ward, A. S., Herzog, S. P., and Wondzell, S. M.: Testing hidden assumptions of representativeness in reach-scale studies of hyporheic exchange, Water Resour. Res., 59, https://doi.org/10.1029/2022WR032718, 2023. 
Bencala, K. E. and Walters, R. A.: Simulation of solute transport in a mountain pool-and-riffle stream: A transient storage model, Water Resour. Res., 19, 718–724, https://doi.org/10.1029/WR019i003p00718, 1983. 
Beven, K. and Binley, A.: The future of distributed models: Model calibration and uncertainty prediction, Hydrol. Process., 6, 279–298, https://doi.org/10.1002/hyp.3360060305, 1992. 
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Short summary
Understanding solute transport often relies on slug tracer experiments. These experiments are biassed toward capturing faster flow paths and miss longer timescales. We explore integrating a slug-injected tracer with naturally occurring radon to quantify flow paths across different timescales at the reach scale. We show that jointly calibrating a transient storage model with both tracers strengthens parameter constraints and improves solute transport estimates in future studies.
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