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| Titel |
Uncertainties in simulating river/groundwater exchanges over the Upper Rhine Graben hydrosystem |
| VerfasserIn |
Jean-Pierre Vergnes, Florence Habets |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250092033
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| Publikation (Nr.) |
 EGU/EGU2014-6358.pdf |
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| Zusammenfassung |
| The Upper Rhine alluvial aquifer is an important transboundary water resource which is
particularly vulnerable to pollution from the rivers due to anthropogenic activities. A realistic
simulation of the groundwater-river exchanges is therefore of crucial importance for an
effective management of water resources. Characterization of these fluxes in term of quantity
and spatio-temporal variability depends on choices made to represent the river water stage
in the model as well as on the hydrogeological parameters. Recently, a coupled
surface-subsurface model has been applied to the whole aquifer basin (Thierion et al., 2012).
The present study aims at improving the estimation of the river/groundwater exchange, and
thus, of the hydrodynamic of the alluvial aquifer, and at getting an idea of the associated
uncertainty by performing a set of simulations that best take advantage of the different kinds
of observed data.
The general modeling strategy is based on the Eau-Dyssée modeling platform which couples
existing specialized models to address water resources quantity and quality in small to
regional scale river basins. In this study, Eau-Dyssée includes the ISBA surface scheme that
estimates the water balance, the RAPID river routing model and the SAM hydrogeological
model. In addition, the QtoZ module (Saleh et al., 2011) is used to calculate the river stage
from simulated river discharges, which is then used to calculate the exchanges between
aquifer units and river, according to three different approaches that are compared: a control
experiment with constant river water stage, a rating curves approach derived from
observed river discharges and river stages, and the Manning’s formula, for which
Manning’s parameters are defined according to geomorphological parameterizations
and topographic data based on Digital Elevation Model (DEM). Supplementary
sensitivity tests are also performed by using different hydrogeological parameter
datasets (porosity and transmissivity). Two sources of DEM were used for this part.
Additionally, sensitivity to the time step of the estimation (daily versus monthly) was
studied.
The evaluation is made against observed water levels and river discharges collected both from
the french and german riversides of the alluvial plain. A heavy network of water table depth
observations is also available to evaluate the simulated piezometric heads. Preliminary results
show that the primary source of errors when simulating river stage – and hence
groundwater-river interactions – is the uncertainties associated with the topographic data used
to define the riverbed elevation. It confirms the need to access to more accurate DEM for
estimating riverbed elevation and studying groundwater-river interactions, at least at regional
scale.
References
Saleh, F., Flipo, N., Habets, F., Ducharne, A., Oudin, L., Viennot, P., Ledoux, E. Modeling
the impact of in-stream water level fluctuations on stream-aquifer interactions at the regional
scale (2011)Journal of Hydrology, 400 (3-4) pp 490-500
Thierion C., Longuevergne L., Habets F. Ledoux E., Ackerer P., Majdalani S., Leblois E.,
Lecluse S., Martin E, Queguiner S., Viennot P., Assessing the water balance of
the Upper Rhine Graben hydrosystem, Journal of Hydrology 424-425 , pp. 68-83 |
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