EGU2020-7713
https://doi.org/10.5194/egusphere-egu2020-7713
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Reconciliation of catchment travel times derived from tritium and deuterium

Julian Klaus1, Nicolas Rodriguez1,2, Laurent Pfister1,3, and Erwin Zehe2
Julian Klaus et al.
  • 1Department of Environmental Research and Innovation, Luxembourg Institute of Science and Technology (LIST), Luxembourg
  • 2Institut für Wasser und Gewässerentwicklung, Karlsruhe Institut für Technologie, Germany
  • 3Faculty of Science, Technology and Medicine, University of Luxembourg, Luxembourg

Catchment travel time distributions (TTDs) are an integrative measure of time-varying flow paths and hydrological processes, commonly derived from tracer data (e.g. 2-H, 3-H). Recently, it has been argued that the use of stable isotopes of O and H compared to tritium neglects the long tails of TTDs and thus truncates our vision on streamflow age. However, the reasons for the truncation of the TTD remain obscured by methodological and data limitations, including different mathematical models and sampling strategies. In this study, we apply composite SAS functions to a forested headwater catchment in Luxembourg, where the complexity of streamflow generation leads to flow paths with highly different TTDs. We calibrate the model with high-frequency (sub-daily) deuterium measurements, as well as nearly 30 tritium stream samples collected over a two-year period. We simulated TTDs based on each tracer individually and jointly. We found that, when using the two tracers in a coherent methodological framework, both tracers result in similar TTD and storage for the studied catchment. We found small differences in the TTDs that might be explained by calculation uncertainties, as well as by the limited sampling frequency for tritium. Using both stable and radioactive isotopes of H as tracers reduced uncertainties in the water age and storage calculations. While tritium and stable isotopes delivered redundant information about younger water, the use of both tracers leveraged the more specific information content of tritium on longer ages in the system. The two tracers had overall different information contents. We found that 30 tritium samples contained more bits of information than approximately 1000 deuterium samples, underlying the importance of complementing stable isotopes studies with tritium data.

How to cite: Klaus, J., Rodriguez, N., Pfister, L., and Zehe, E.: Reconciliation of catchment travel times derived from tritium and deuterium, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-7713, https://doi.org/10.5194/egusphere-egu2020-7713, 2020

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