USING PRINCIPAL COMPONENTS-ANALYSIS AND NA CL RATIOS TO TRACE GROUNDWATER CIRCULATION IN A VOLCANIC ISLAND - THE EXAMPLE OF REUNION/

The development of the limited groundwater resources of a remote tropi cal island, in particularly rugged volcanic terrain, requires a thorou gh understanding of the hydrogeology. The cost of a classical approach by borehole investigations often precludes a 'reasoned' approach, res ulting in a somewhat haphazard development of resources with varying s uccess. This paper describes the use of multivariate statistical analy is to trace groundwater circulation in volcanic terrains. The method i nvolves the use of principal components analysis (PCA) based on both s tructural and hydrochemical parameters of 243 springs of Reunion (west ern Indian Ocean). As a result, we propose the use of Na/Cl analysis i n differentiating three types of volcanic aquifers. This analysis is c onsistent with a geological and hydrogeological conceptual model devel oped from a combined hydrochemical and geological reconnaissance of 27 springs. (C) 1997 Elsevier Science B.V.