Mapping groundwater quality variables using PCA and geostatistics: a case study of Bajo Andarax, southeastern Spain

A case study is presented for the application of statistical and geostatist ical methods to the problem of estimating groundwater quality variables. Th is methodology has been applied to the investigation of the detrital aquife r of the Bajo Andarax (Almeria, Spain). The use of principal components ana lysis is proposed, as a first step, for identifying relevant types of groun dwater and the processes that bring about a change in their duality. As a r esult of this application, three factors were obtained, which were used as three new variables (V1: sulphate influence; V2: thermal influence; and V3: marine influence). Analysis of their spatial distribution was performed th rough the calculation of experimental and theoretical variograms, which ser ved as input for geostatistical modelling using ordinary block kriging. Thi s analysis has allowed a probabilistic representation of the data to be obt ained by mapping the three variables throughout the aquifer fur each sampli ng point. In this way, one can evaluate the spatial and temporal variation of the principal physico-chemical processes associated with the three varia bles V1, V2, and V3 implicated in the groundwater quality of the detrital a quifer.