Abstract
Abstract. Rohrschollen Island is an artificial island of the large Upper Rhine river whose geometry and hydrological dynamics are the result of engineering works during the 19th and 20th centuries. Before its channelization, the Rhine river was characterized by an intense hydromorphological activity which maintained a high level of biodiversity along the fluvial corridor. This functionality considerably decreased during the two last centuries. In 2012, a restoration project was launched to reactivate typical alluvial processes, including bedload transport, lateral channel dynamics, and surface–subsurface water exchanges. An integrated hydrological model has been applied to the area of Rohrschollen Island to assess the efficiency of the restoration regarding surface and subsurface flows. This model is calibrated using measured piezometric heads. Simulated patterns of water exchanges between the surface and subsurface compartments of the island are checked against the information derived from thermal infrared (TIR) imaging. The simulated results are then used to better understand the evolutions of the infiltration–exfiltration zones over time and space and to determine the physical controls of surface–subsurface interactions on the hydrographic network of Rohrschollen Island. The use of integrated hydrological modeling has proven to be an efficient approach to assess the efficiency of restoration actions regarding surface and subsurface flows.
Highlights
Interactions between surface and subsurface flow processes are key components of the continental hydrological cycle (Winter et al, 1998; Sophocleous, 2002), which have received particular attention in the last decades partly because of their substantial impact on the overall response of hydrologic systems (Boano et al, 2014; Brunner et al, 2017, and citations )
As the pre-restored island is not well documented in terms of hydraulic data, we considered a scenario where the pre-restored island is similar to the current situation with the exception that the newly excavated channel connecting Rohrschollen Island’s BGW and the Rhine river is absent
As the interactions between surface and subsurface compartments of the hydrosystem have a strong impact on hydrological, biogeochemical, and ecological processes, it makes sense to rely upon integrated hydrological modeling when addressing the question of restoration efficiency
Summary
Interactions between surface and subsurface flow processes are key components of the continental hydrological cycle (Winter et al, 1998; Sophocleous, 2002), which have received particular attention in the last decades partly because of their substantial impact on the overall response of hydrologic systems (Boano et al, 2014; Brunner et al, 2017, and citations ). Several studies have recently highlighted the hydrological interactions between surface and subsurface that have a major impact on the biogeochemical and ecological responses of hydrosystems (e.g., Stegen et al, 2016, 2018; Danczak et al, 2016; Partington et al, 2017) These interactions, which are partly driven by the geomorphological structure and the channel dynamics (Namour et al, 2015), influence flow pathways, water mixing, residence time in the hyporheic zone along streambeds, and the overall ecological functioning (Schmitt et al, 2011). This study is limited to the analysis of the short-term response (to flood events that are pulse stresses) of a transient hydrosystem via a highly resolved model in time and space
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