Evaluating the impact of river restoration on the local groundwater and ecological system: a case study in NE Flanders
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Date
2011
Authors
Rogiers, Bart
Lermytte, Johan
De Bie, Els
Batelaan, Okke
Journal Title
Journal ISSN
Volume Title
Publisher
University of Liege, Belgium
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Rights Holder
Abstract
River restoration changes the interaction between groundwater and surface water. Therefore, it is expected
to have an impact on ecosystems at the interface between groundwater and surface water. Quantifying and generalizing
the level of change of this interaction for different hydrogeological environments is scientifically and practically
challenging. In this paper we investigated the impact of different restoration measures and the effect on the interaction of
the temporal resolution of the groundwater modeling methodology. The interaction is analysed in the water bodies and
wetlands in the valley of the Zwarte Beek, one of the most valuable nature reserves of Flanders. In the past, several
changes have been made to the river and drainage system. These adaptations are now considered to be bottlenecks in
maintaining a good ecological and hydrological status of its water dependent biotopes. Hence, in the context of the EU
Water Framework Directive, it is necessary to (at least partly) restore the initial natural situation. The measures proposed
include the reinstatement of old meanders and the removal of a weir. By removing the weir, fish migration is again
possible. Reconnecting old meanders increases the habitat diversity. We used transient groundwater modeling to evaluate
the impact on the groundwater system of the wetlands. Results indicate that a peat layer, present in most of the wetland,
minimizes the effects of the restoration on the groundwater table. The largest changes are confined to the areas near the
old meanders and the weir. Steady-state situations do not allow a calculation of average lowest and highest groundwater
levels, which are essential for simulating ecological site conditions. Hence, transient simulations with 14 days time steps
are required to detect a considerably greater range of groundwater fluctuation than indicated by the seasonal simulation.
It is shown that the river restoration project thus resulted in an improvement of the structure of the watercourse rather than
the rewetting of the valley. We concluded also that high resolution transient groundwater modeling is an essential step
towards river restoration and ecohydrological predictions.
Description
Keywords
Belgium, Water, Groundwater, River restoration, Conceptual modelling
Citation
Rogiers, B., Lermytte, J., De Bie, E. and Batelaan, O., 2011. Evaluating the impact of river restoration on the local groundwater and ecological system: a case study in NE Flanders. Geologica Belgica, 14 (3-4), 265-276.