Présentations Colloques

Flash Poster
8.09
Session 8.09: Hydrogeoecology: a focus on groundwater ecology
Kozel Ronald
Linkage of ecological and hydrodynamic aquifer parameters
Ecological issues represent a supplementary tool for the characterization of groundwater resources and may furthermore contribute to identify hydrodynamic processes and to act as water quality indicators. Consequently, the Swiss Water Protection Ordinance not only defines microbiological and chemical water quality standards but also ecological objectives for groundwater. The ordinance states that biocenoses in groundwater should be in a “natural state adapted to the habitat” and “characteristic of groundwater that is not or only slightly polluted”. However, today experts are still looking for approaches to carry out such assessments.**In this context, two studies have recently been performed in the framework of the NAQUA National Groundwater Monitoring for testing both microbiological and faunal approaches to obtain better understanding of regional groundwater ecology in Switzerland as well as its correlation with hydrogeological information. Sampling at 50 representative monitoring sites for microbiological parameters – specifically for total cell count, measured by flow-cytometry – provided typical ranges of bacterial density between 10e3 and 10e6 cells per mL. Selected springs were sampled for faunal assemblages, resulting in up to 10 individuals per m3 of discharge. Assemblages found at the sites showed a high diversity, with a total of 40 species. Results of both abundance and species composition indicate that global aquifer vulnerability and surface water influence may play a more important role than spatial or seasonal variations. Highly vulnerable karst aquifers were dominated by a high abundance of stygophilic species while less vulnerable systems which are more protected from surface water infiltration were represented by stygobiontic species. **The degree of surface water influence and groundwater vulnerability could thus be directly derived from both ecological parameters and the stygophiles stygobionts-ratio. The findings are consistent with intrinsic aquifer parameters, such as spring discharge variability, and are in agreement with physico-chemical as well as other microbiological data from the sites. Both approaches seem to represent a potential for defining the ecological state of the groundwater biocenosis and indicating aquifers hydrodynamics, vulnerability and groundwater quality.**
Switzerland