Understanding mean transit times in Andean tropical montane cloud forest catchments: combining tracer data, lumped parameter models and uncertainty analysis.
Weekly samples from surface waters, springs, soil water and rainfall were collected in a 76.9 km2 mountain rain forest catchment and its tributaries in southern Ecuador. Time series of the stable water isotopes ? 18O and ? 2H were used to calculate mean transit times (MTTs) and the transit ti...
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Formato: | Artículos |
Lenguaje: | eng |
Publicado: |
2016
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Materias: | |
Acceso en línea: | http://repositorio.educacionsuperior.gob.ec/handle/28000/2791 |
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Sumario: | Weekly samples from surface waters, springs, soil
water and rainfall were collected in a 76.9 km2 mountain
rain forest catchment and its tributaries in southern Ecuador.
Time series of the stable water isotopes ?
18O and ?
2H were
used to calculate mean transit times (MTTs) and the transit
time distribution functions (TTDs) solving the convolution
method for seven lumped-parameter models. For each
model setup, the generalized likelihood uncertainty estimation
(GLUE) methodology was applied to find the best predictions,
behavioral solutions and parameter identifiability.
For the study basin, TTDs based on model types such as
the linear?piston flow for soil waters and the exponential?
piston flow for surface waters and springs performed better
than more versatile equations such as the gamma and the two
parallel linear reservoirs. Notwithstanding both approaches
yielded a better goodness of fit for most sites, but with considerable
larger uncertainty shown by GLUE. Among the
tested models, corresponding results were obtained for soil
waters with short MTTs (ranging from 2 to 9 weeks). For
waters with longer MTTs differences were found, suggesting
that for those cases the MTT should be based at least
on an intercomparison of several models. Under dominant
baseflow conditions long MTTs for stream water ? 2 yr were
detected, a phenomenon also observed for shallow springs.
Short MTTs for water in the top soil layer indicate a rapid
exchange of surface waters with deeper soil horizons. Differences
in travel times between soils suggest that there is
evidence of a land use effect on flow generation. |
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