Geologist and doctor of quantitative hydrogeology, Patrick Lachassagne has focused his expertise and research activity on complex aquifers: groundwater in crystalline, volcanic, karst and glacial basement regions, natural, thermal and geothermal mineral water aquifers. It has led to a major evolution in scientific concepts concerning the structure and hydrogeological functioning of fractured basement aquifers (plutonic and metamorphic rocks): it has demonstrated that their permeability is due to supergenic alteration processes and has resulted in many operational applications in hydrogeology. For more than 20 years at BRGM, he has participated in the development of specific methodologies for the recognition, management, modelling and protection of these complex aquifers, during operational and research projects in metropolitan France, in DROM-COM and abroad. For nearly 9 years, he has been pursuing this activity, combining research and operational work for Danone Eaux on the natural mineral water deposits of Evian, Volvic, Badoit and La Salvetat and, more occasionally, internationally. Patrick Lachassagne provides regular university teaching and professional training. Since 2014, he has created and managed the "Water Institute by Evian" (www.waterinstitutebyevian.org). He is a certified hydrogeologist and vice-president of the French Committee of Hydrogeology of the Association Internationale des Hydrogéologues.