Spatially distributed tracer-aided runoff modelling and dynamics of storage and water ages in a permafrost-influenced catchment
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Abstract. Permafrost strongly controls hydrological processes in cold regions. Our
understanding of how changes in seasonal and perennial frozen ground
disposition and linked storage dynamics affect runoff generation processes
remains limited. Storage dynamics and water redistribution are influenced by
the seasonal variability and spatial heterogeneity of frozen ground, snow
accumulation and melt. Stable isotopes are potentially useful for quantifying the
dynamics of water sources, flow paths and ages, yet few studies have employed
isotope data in permafrost-influenced catchments. Here, we applied the
conceptual model STARR (the Spatially distributed Tracer-Aided Rainfall–Runoff model), which facilitates fully distributed simulations of hydrological
storage dynamics and runoff processes, isotopic composition and water ages.
We adapted this model for a subarctic catchment in Yukon Territory, Canada,
with a time-variable implementation of field capacity to include the
influence of thaw dynamics. A multi-criteria calibration based on stream
flow, snow water equivalent and isotopes was applied to 3Â years of data.
The integration of isotope data in the spatially distributed model provided
the basis for quantifying spatio-temporal dynamics of water storage and ages,
emphasizing the importance of thaw layer dynamics in mixing and damping the
melt signal. By using the model conceptualization of spatially and temporally
variable storage, this study demonstrates the ability of tracer-aided
modelling to capture thaw layer dynamics that cause mixing and damping of the
isotopic melt signal.
