Présentations Colloques

Flash Poster
Session 8.03: Geometrical structure and hydrogeological properties of Hard-Rock aquifers.
Gandolfi Jean Marie
A multi-scale and multi-partner program in search of water within hard rock aquifers- from decision making tool to the borehole completion and use
The eastern part of the region Midi-Pyrénées (south-western Massif central, France), about 7500 kmC, mainly stands on hard rock formations. This area has low density population with limited ability to tap surface water or small spring water due to their significant seasonal variations (drying during summer). This setting challenges water supply for human and livestock watering. This context has led to a multi-year process to gather every stakeholders working in the field of water resource, from research community to local water supply managing body.First the BRGM (French Geological Survey) developed a decision making tool map (GIS) at regional scale based on scientific findings from geological research on the ability for hard rock formations to develop a weathered, productive aquifer.Then, the Department of Lot wished to use this tool in order to tap new hard rock groundwater resources within the Ségala district to help local water supply managing company.The Department of Lot was assisted by the consultancy company Calligée in identifying sites with the highest profile based on technical and human multicriteria assessment. Geophysical investigations were used in the field for these high profile sites to set the final locations of the exploratory drillings which were tested consecutively.This initiative has been supported financially all along by the Adour-Garonne Water Agency, from the very first steps, with research and development, to the last steps, with in the field implementation, meanwhile gathering feedback to consolidate further similar process.This approach allowed for the work to focus on the best profile sites, offering a diversity of exploration techniques to further improve wells location. The field results of the pumping tests completed are promising and it paved the way for similar integrated process to be implemented to increase success rates for productive water well drilling within hard rock aquifers.