IWRA Proceedings

AbstractThe centre of Corsica has high relief with altitudes greater than 2500m. The most recent modulus of pluviometry of this region (Meteo France data) evolved from 700mm to more than 1500mm per year. The infiltrated water contributes to feeding different aquifers, the organisation of which is related to regional tectonic. Corsica is made of two major units: to the West, the old Corsica which is constituted by a succession of hercynian granite, and to the East the alpine Corsica. These two units are separated by a major fault. This is marked out by units of different origins, containing, in particular in the region of Corte imbricated slices. They are composed of an inverted series formed by units which range from the carbonates of the Triassic to the residue of the Upper Jurassic. This geological and geomorpholigical complexity is mirrored by the diversity of the hydrogeology. As example, we present here the characterization of three aquifers drained by springs located on a zone of only 10 km in the Corte region : Noceta (fissured basement), Minesteghju (binar karstic) and Bistuglio (fissured and karstic). The concentrations of major elements plotted on Piper and Schöeller-Berkalof diagrams show two families of waters : the first one, bicarbonated calcic and sodic corresponding to siliceous rocks ; the second one, bicarbonated calcic and magnesian corresponds to carbonated environment. The mean conductivity is linked with the nature of the rocks : 50 µS.cm-1 for Noceta (siliceous rocks), 300 µS.cm-1 for Ministeghju (Limestones of Lias), 600 µS.cm-1 for Bistuglio (dolomitic limestones of upper Trias). The continual recording of the physical-chemical parameters of the source of Minesteghju permits us to conclude that almost 50% of the waters have a short residence, marked by the conductivity between 100 and 350 µS/cm. The next half, of stronger conductivity (400 a 500 µS/cm), corresponds to the reserves of the aquifers. Variations of conductivity, temperature and pH versus pluviometry and discharge permit the description of the behaviour of an apparently complex aquifer. In this region the underground waters, although they are neglected for the drinking water supply, could be used as a substitute, and or a complement or as a principal resource for the small communities. This means an integrated and durable management, and or good knowledge of the aquifers of the mountain, is required. References : 1. Dörflinger N., Ferrandini J., Ferrandini M. & Mathieu F., 2002. Caractérisation géométrique et hydrodynamique du Causse de Bonifacio (Corse) à partir d’une synthèse des connaissances géologiques et hydrogéologiques et par méthodes géophysiques. – BRGM/R-51860-FR. 2. Ferrandini J., Griolet C., Gauthier A. et Ferracci-Ceccaldi J.-J., 2006. Hydrogéologie de la Corse, 758-766. in « Aquifères et eaux souterraines de France » Ouvrage collectif sous la direction de J.-C ; Roux, BRGM Edition.