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| Titel |
Modeling nutrient in-stream processes at the watershed scale using Nutrient Spiralling metrics |
| VerfasserIn |
R. Marcé, J. Armengol |
| 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 ; 13, no. 7 ; Nr. 13, no. 7 (2009-07-06), S.953-967 |
| Datensatznummer |
250011923
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| Publikation (Nr.) |
 copernicus.org/hess-13-953-2009.pdf |
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| Zusammenfassung |
One of the fundamental problems of using large-scale biogeochemical
models is the uncertainty involved in aggregating the components of
fine-scale deterministic models in watershed applications, and in
extrapolating the results of field-scale measurements to larger
spatial scales. Although spatial or temporal lumping may reduce the
problem, information obtained during fine-scale research may not apply
to lumped categories. Thus, the use of knowledge gained through
fine-scale studies to predict coarse-scale phenomena is not
straightforward. In this study, we used the nutrient uptake metrics
defined in the Nutrient Spiralling concept to formulate the equations
governing total phosphorus in-stream fate in a deterministic, watershed-scale
biogeochemical model. Once the model was calibrated, fitted phosphorus
retention metrics where put in context of global patterns of phosphorus
retention variability. For this purpose, we calculated power regressions
between phosphorus retention metrics, streamflow, and phosphorus concentration
in water using published data from 66 streams worldwide, including both
pristine and nutrient enriched streams.
Performance of the calibrated model confirmed that the Nutrient Spiralling
formulation is a convenient simplification of the biogeochemical
transformations involved in total phosphorus in-stream fate. Thus,
this approach may be helpful even for customary deterministic applications
working at short time steps. The calibrated phosphorus retention metrics
were comparable to field estimates from the study watershed, and showed high
coherence with global patterns of retention metrics from streams of the world.
In this sense, the fitted phosphorus retention metrics were similar to field
values measured in other nutrient enriched streams. Analysis of the bibliographical
data supports the view that nutrient enriched streams have lower phosphorus
retention efficiency than pristine streams, and that this efficiency loss
is maintained in a wide discharge range. This implies that both small and
larger streams may be impacted by human activities in terms of nutrient
retention capacity, suggesting that larger rivers located in human populated
areas can exert considerable influence on phosphorus exports from watersheds.
The role of biological activity in this efficiency loss showed by nutrient
enriched streams remained uncertain, because the phosphorus mass transfer
coefficient did not show consistent relationships with streamflow and phosphorus
concentration in water. The heterogeneity of the compiled data and the possible
role of additional inorganic processes on phosphorus in-stream dynamics may
explain this. We suggest that more research on phosphorus dynamics at the
reach scale is needed, specially in large, human impacted watercourses. |
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