Présentations Colloques

    Session 5.05: Groundwater and Ecosystems – Hydrological role of forests and wetlands
    Ros (orateur)
    Groundwater-surface water interaction and related groundwater dependant ecosystems - case study of the Natura 2000 wetlands of the Crau plain (SE France)
    According to the European Water Framework Directive (2000 60 EC) and groundwater directive (2006 18 EC), groundwater and surface water dependent ecosystems have to be protected. Thus, management protocols need to be implemented at the watershed scale in order to reduce water uptakes, e.g. for agriculture, and to restore the required volumes toward ecosystems. In the Crau plain (SE France), grassland production depends essentially on traditional flooded irrigation practices, with water derived from the Durance river. The large amount of irrigation return flow represents nearly 70% of the Crau aquifer recharge. This large-scale artificial recharge thus becomes essential for some directly connected wetlands. In the present global change context, pressure on the Durance River resource is rising. Therefore, it is imperative to quantify water requirements of wetlands directly or indirectly supplied by Durance River and to find the optimal balance between water saving and ecosystem demand.**The present study constitutes a preliminary diagnosis about groundwater resurgences of the Crau aquifer, named laurons . Outflows of these poorly known springs provide water to a remarkable wetland ecosystem, maintaining numerous habitats for biological species including glacial relics. These wetlands are classified as Special Protection Area (Natura 2000). The overall objective of the study is to estimate the importance of these laurons in maintaining the ecosystem of the Crau wetlands and to model their evolution according to the hydrodynamic changes in groundwater flows especially in response to irrigation. The proposed multi-criteria analysis aims to determine the hydrodynamics and hydrochemical characteristics of these laurons (water budget, flow-rates and directions, physicochemical parameters and major ions), and their connections with the aquifer using geochemical tracers (stable isotopes in water and radon). This analysis will provide new insights on the surface water - groundwater interactions necessary for the preservation of these fragile ecosystems.**


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