Temporal dynamics of catchment transit times from stable isotope data

Julian Klaus*, Kwok Pan CHUN, Kevin J. McGuire, Jeffrey J. McDonnell

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

48 Citations (Scopus)

Abstract

Time variant catchment transit time distributions are fundamental descriptors of catchment function but yet not fully understood, characterized, and modeled. Here we present a new approach for use with standard runoff and tracer data sets that is based on tracking of tracer and age information and time variant catchment mixing. Our new approach is able to deal with nonstationarity of flow paths and catchment mixing, and an irregular shape of the transit time distribution. The approach extracts information on catchment mixing from the stable isotope time series instead of prior assumptions of mixing or the shape of transit time distribution. We first demonstrate proof of concept of the approach with artificial data; the Nash-Sutcliffe efficiencies in tracer and instantaneous transit times were >0.9. The model provides very accurate estimates of time variant transit times when the boundary conditions and fluxes are fully known. We then tested the model with real rainfall-runoff flow and isotope tracer time series from the H.J. Andrews Watershed 10 (WS10) in Oregon. Model efficiencies were 0.37 for the 18O modeling for a 2 year time series; the efficiencies increased to 0.86 for the second year underlying the need of long time tracer time series with a long overlap of tracer input and output. The approach was able to determine time variant transit time of WS10 with field data and showed how it follows the storage dynamics and related changes in flow paths where wet periods with high flows resulted in clearly shorter transit times compared to dry low flow periods. Key Points: Approach for time variant catchment transit time Modeling irregular shape of transit time distributions by time variant mixing Modeling catchment transit time in WS10 of HJA Forest

Original languageEnglish
Pages (from-to)4208-4223
Number of pages16
JournalWater Resources Research
Volume51
Issue number6
DOIs
Publication statusPublished - 1 Jun 2015

Scopus Subject Areas

  • Water Science and Technology

User-Defined Keywords

  • catchment
  • runoff generation
  • stable isotopes
  • transit time

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