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| Titel |
A channel transmission losses model for different dryland rivers |
| VerfasserIn |
A. C. Costa, A. Bronstert, J. C. Araújo |
| 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 ; 16, no. 4 ; Nr. 16, no. 4 (2012-04-03), S.1111-1135 |
| Datensatznummer |
250013253
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| Publikation (Nr.) |
 copernicus.org/hess-16-1111-2012.pdf |
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| Zusammenfassung |
| Channel transmission losses in drylands take place normally in extensive
alluvial channels or streambeds underlain by fractured rocks. They can play
an important role in streamflow rates, groundwater recharge, freshwater
supply and channel-associated ecosystems. We aim to develop a
process-oriented, semi-distributed channel transmission losses model, using
process formulations which are suitable for data-scarce dryland environments
and applicable to both hydraulically disconnected losing streams and
hydraulically connected losing(/gaining) streams. This approach should be
able to cover a large variation in climate and hydro-geologic controls,
which are typically found in dryland regions of the Earth. Our model was
first evaluated for a losing/gaining, hydraulically connected 30 km reach of
the Middle Jaguaribe River (MJR), Ceará, Brazil, which drains a
catchment area of 20 000 km2. Secondly, we applied it to a small
losing, hydraulically disconnected 1.5 km channel reach in the Walnut Gulch
Experimental Watershed (WGEW), Arizona, USA. The model was able to predict
reliably the streamflow volume and peak for both case studies without using
any parameter calibration procedure. We have shown that the evaluation of
the hypotheses on the dominant hydrological processes was fundamental for
reducing structural model uncertainties and improving the streamflow
prediction. For instance, in the case of the large river reach (MJR), it was
shown that both lateral stream-aquifer water fluxes and groundwater flow in
the underlying alluvium parallel to the river course are necessary to
predict streamflow volume and channel transmission losses, the former
process being more relevant than the latter. Regarding model uncertainty, it
was shown that the approaches, which were applied for the unsaturated zone
processes (highly nonlinear with elaborate numerical solutions), are much
more sensitive to parameter variability than those approaches which were
used for the saturated zone (mathematically simple water budgeting in
aquifer columns, including backwater effects). In case of the
MJR-application, we have seen that structural uncertainties due to the
limited knowledge of the subsurface saturated system interactions
(i.e. groundwater coupling with channel water; possible groundwater flow parallel
to the river) were more relevant than those related to the subsurface
parameter variability. In case of the WEGW application we have seen that the
non-linearity involved in the unsaturated flow processes in disconnected
dryland river systems (controlled by the unsaturated zone) generally contain
far more model uncertainties than do connected systems controlled by the
saturated flow. Therefore, the degree of aridity of a dryland river may be
an indicator of potential model uncertainty and subsequent attainable
predictability of the system. |
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