Spatial and Multivariate Analysis of Groundwater Hydrochemistry in the Solana Aquifer, SE Spain

Abstract

The Solana aquifer is located in the South-East of the Iberian Peninsula and forms part of the Villena-Benejama groundwater body. It is a limestone and dolomite aquifer that has historically been considered overexploited due to intensive agriculture and urban use. Despite this, the quality of the water has remained stable over time. This study analyses the spatial and temporal variability within the aquifer and identifies the controlling processes. Chemical analyses were conducted on samples taken from 26 wells in July 2024 and February 2025. The results reveal a predominant calcium carbonate facies with minimal seasonal variation. However, sulphate-chloride water was found in the South-Western sector, which is associated with the dissolution of evaporitic materials from the Triassic Keuper. Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) identified two processes: a salinity gradient linked to lithology, and a second process related to bicarbonates and nitrates, indicating potential nitrate inputs in the eastern half of the aquifer. HCA differentiates four clusters: one highly mineralised group located in the south-western sector near Triassic outcrops, two intermediate groups with slight differences in composition and distribution, and a fourth group with the lowest mineralisation located on the Southern flank of the Solana range.