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| Titel |
Understanding uncertainties when inferring mean transit times of water trough tracer-based lumped-parameter models in Andean tropical montane cloud forest catchments |
| VerfasserIn |
E. Timbe, D. Windhorst, P. Crespo, H.-G. Frede, J. Feyen, L. Breuer |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 18, no. 4 ; Nr. 18, no. 4 (2014-04-24), S.1503-1523 |
| Datensatznummer |
250120339
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| Publikation (Nr.) |
 copernicus.org/hess-18-1503-2014.pdf |
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| Zusammenfassung |
| 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
δ18O and δ2H 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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