Challenge: To assess and define the vulnerability of the aquifer, establish sustainable exploitation conditions, and determine protection perimeters.
Solution: INTERA conducted hydrogeological and hydrodispersive modelling for the lower Romanche alluvial plain in support of ensuring the long-term security and quality of water resources for both public consumption and industrial use. To address the aquifer’s complex geological structure, characterised by a complex fluvio-glacial structure with significant variations in alluvial deposit thickness and bedrock slope, we developed a detailed 3D geological model using Leapfrog to produce elevation contact surfaces between geological layers and model 3-D volumes for each layer. A FEFLOW groundwater model was developed with multiscale spatial discretisation, required to accurately model small-scale catchment fields and large-scale regional flows. The aquifer's interaction with the surface hydrographic network also posed challenges. We developed a HEC-RAS hydraulic surface water model to simulate transient groundwater flow and account for temporal variations in boundary conditions. This model allowed FEFLOW to implement flexible and accurate temporal variations in surface water conditions, critical for capturing the dynamic nature of groundwater-river interactions. The FEFLOW model was calibrated using PEST, and demonstrated a high level of accuracy across different spatial scales.
Results: INTERA’s model provided detailed quantitative insights into the alluvial aquifer, including 1) the identification of recharge zones for drinking water supply catchments, 2) an analysis of underground flow dynamics and quantification of exchange rates with surface water bodies, and 3) the average age of water within various layers of the aquifer. These outcomes are helping define protection perimeters that safeguard the aquifer from contamination and overexploitation, thereby ensuring a reliable water supply for the region.
