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Spatially distributed modelling of surface water-groundwater exchanges during overbank flood events – a case study at the Garonne River

Bernard-Jannin, Léonard and Brito, David and Sun, Xiaoling and Jauch, Eduardo and Neves, Ramiro and Sauvage, Sabine and Sanchez-Pérez, José-Miguel Spatially distributed modelling of surface water-groundwater exchanges during overbank flood events – a case study at the Garonne River. (2016) Advances in Water Resources, 94. 146-159. ISSN 0309-1708

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Official URL: http://dx.doi.org/10.1016/j.advwatres.2016.05.008

Abstract

Exchanges between surface water (SW) and groundwater (GW) are of considerable importance to flood- plain ecosystems and biogeochemical cycles. Flood events in particular are important for riparian water budget and element exchanges and processing. However SW-GW exchanges present complex spatial and temporal patterns and modelling can provide useful knowledge about the processes involved at the scale of the reach and its adjacent floodplain. This study used a physically-based, spatially-distributed mod- elling approach for studying SW-GW exchanges. The modelling in this study is based on the MOHID Land model, combining the modelling of surface water flow in 2D with the Saint-Venant equation and the modelling of unsaturated groundwater flow in 3D with the Richards’ equation. Overbank flow dur- ing floods was also integrated, as well as water exchanges between the two domains across the entire floodplain. Conservative transport simulations were also performed to study and validate the simulation of the mixing between surface water and groundwater. The model was applied to the well-monitored study site of Monbéqui (6.6 km ²) in the Garonne floodplain (south-west France) for a five-month period and was able to represent the hydrology of the study area. Infiltration (SW to GW) and exfiltration (SW to GW) were characterised over the five-month period. Results showed that infiltration and exfiltration exhibited strong spatiotemporal variations, and infiltration from overbank flow accounted for 88% of the total simulated infiltration, corresponding to large flood periods. The results confirmed that overbank flood events played a determinant role in floodplain water budget and SW-GW exchanges compared to smaller (below bankfull) flood events. The impact of floods on water budget appeared to be similar for flood events exceeding a threshold corresponding to the five-year return period event due to the study area’s topography. Simulation of overbank flow during flood events was an important feature in the ac- curate assessment of exchanges between surface water and groundwater in floodplain areas, especially when considering large flood events.

Item Type:Article
Additional Information:Thanks to Elsevier editor. The definitive version is available at http://www.sciencedirect.com/science/article/pii/S0309170816301373
HAL Id:hal-01348632
Audience (journal):International peer-reviewed journal
Uncontrolled Keywords:
Institution:French research institutions > Centre National de la Recherche Scientifique - CNRS (FRANCE)
Université de Toulouse > Institut National Polytechnique de Toulouse - INPT (FRANCE)
Université de Toulouse > Université Toulouse III - Paul Sabatier - UPS (FRANCE)
Other partners > Universidade Nova de Lisboa - UNL (PORTUGAL)
Laboratory name:
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Deposited By: Leonard BERNARD-JANIN
Deposited On:25 Jul 2016 10:02

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