Using principal components analysis and Na/Cl ratios to trace groundwater circulation in a volcanic island: the example of Reunion

Abstract : The development of the limited groundwater resources of a remote tropical island, in particularly rugged volcanic terrain, requires a thorough understanding of the hydrogeology. The cost of a classical approach by borehole investigations often precludes a ‘reasoned’ approach, resulting in a somewhat haphazard development of resources wuth varying success. This paper describes the use of multivariate statistical analysis to trace groundwater circulation in volcanic terrains. The method involves the use of principal components analysis (PCA) based on both structural and hydrochemical parameters of 243 springs of Reunion (western Indian Ocean). As a result, we propose the use of Na/Cl analysis in differentiating three types of volcanic aquifers. This analysis is consistent with a geological and hydrogeological conceptual model developed from a combined hydrochemical and geological reconnaissance of 27 springs.