Conceptual modelling to assess how the interplay of hydrological connectivity, catchment storage and tracer dynamics controls nonstationary water age estimates

Christian Birkel*, Chris Soulsby, Doerthe Tetzlaff

*Corresponding author for this work

Research output: Contribution to journalArticle

60 Citations (Scopus)
20 Downloads (Pure)

Abstract

Although catchment storage is an intrinsic control on the rainfall-runoff response of streams, direct measurement remains a major challenge. Coupled models that integrate long-term hydrometric and isotope tracer data are useful tools that can provide insights into the dynamics of catchment storage and the volumes of water involved. In this study, we use a tracer-aided hydrological model to characterize catchment storage as a dynamic control on system function related to streamflow generation, which also allows direct estimation of the nonstationarity of water ages. We show that in a wet Scottish upland catchment dominated by runoff generation from riparian peats (histosols) with high water storage, nonstationarity in water age distributions is only clearly detectable during more extreme wet and dry periods. This is explained by the frequency and longevity of hydrological connectivity and the associated relative importance of flow paths contributing younger or older waters to the stream. Generally, these saturated riparian soils represent large mixing zones that buffer the time variance of water age and integrate catchment-scale partial mixing processes. Although storage simulations depend on model performance, which is influenced by input variability and the degree of isotopic damping in the stream, a longer-term storage analysis of this model indicates a system that is only sensitive to more extreme hydroclimatic variability.

Original languageEnglish
Pages (from-to)2956-2969
Number of pages14
JournalHydrological Processes
Volume29
Issue number13
Early online date8 Jan 2015
DOIs
Publication statusPublished - Jun 2015

Fingerprint

connectivity
tracer
catchment
modeling
water
runoff
Histosol
buffer zone
water storage
age structure
damping
streamflow
isotope
rainfall
simulation
soil

Keywords

  • catchment storage
  • water age
  • rainfall-runoff model
  • tracers
  • stable isotopes
  • connectivity

ASJC Scopus subject areas

  • Water Science and Technology

Cite this

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title = "Conceptual modelling to assess how the interplay of hydrological connectivity, catchment storage and tracer dynamics controls nonstationary water age estimates",
abstract = "Although catchment storage is an intrinsic control on the rainfall-runoff response of streams, direct measurement remains a major challenge. Coupled models that integrate long-term hydrometric and isotope tracer data are useful tools that can provide insights into the dynamics of catchment storage and the volumes of water involved. In this study, we use a tracer-aided hydrological model to characterize catchment storage as a dynamic control on system function related to streamflow generation, which also allows direct estimation of the nonstationarity of water ages. We show that in a wet Scottish upland catchment dominated by runoff generation from riparian peats (histosols) with high water storage, nonstationarity in water age distributions is only clearly detectable during more extreme wet and dry periods. This is explained by the frequency and longevity of hydrological connectivity and the associated relative importance of flow paths contributing younger or older waters to the stream. Generally, these saturated riparian soils represent large mixing zones that buffer the time variance of water age and integrate catchment-scale partial mixing processes. Although storage simulations depend on model performance, which is influenced by input variability and the degree of isotopic damping in the stream, a longer-term storage analysis of this model indicates a system that is only sensitive to more extreme hydroclimatic variability.",
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author = "Christian Birkel and Chris Soulsby and Doerthe Tetzlaff",
note = "Acknowledgements We would like to gratefully acknowledge the data provided by SEPA, Iain Malcolm. Mark Speed, Susan Waldron and many MSS staff helped with sample collection and lab analysis. We thank the European Research Council (project GA 335910 VEWA) for funding and are grateful for the constructive comments provided by three anonymous reviewers.",
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AU - Birkel, Christian

AU - Soulsby, Chris

AU - Tetzlaff, Doerthe

N1 - Acknowledgements We would like to gratefully acknowledge the data provided by SEPA, Iain Malcolm. Mark Speed, Susan Waldron and many MSS staff helped with sample collection and lab analysis. We thank the European Research Council (project GA 335910 VEWA) for funding and are grateful for the constructive comments provided by three anonymous reviewers.

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