Abstract. Principal Component Analysis (PCA) and Hierarchical Cluster Analysis (HCA) were applied in the groundwater hydrochemical parameters dataset of the Tirnavos alluvial sub basin-central Greece. PCA results suggest occurrence of four principal components both for dry and wet periods. Results of HCA application enabled to divide groundwater samples into two major groups with a large disparity in the number of samples for both periods. Implementation of these methods and spatial distribution of their corresponding results assist revealing key hydrodynamic evolution patterns and hydrochemical dependencies to anthropogenic and geogenic factors.