Statistical analysis of the hydrogeochemical evolution of groundwater in hard and sedimentary aquifers system of Gadilam river basin, South India

The study of groundwater hydrogeochemistry of hard and sedimentary aquifers system in Gadilam river basin has resulted in a large number of geochemical dataset. Groundwater samples were collected at 41 sites over spread of 1380 km2 study area and analysed for major ions. The large number of data can lead to difficulties in the integration, interpretation and representation of the results. Application of statistical analysis of the data helps us to unravel the hidden relationship between ions. Correlation analyses and factor analyses were applied to classify the groundwater samples, and to identify geochemical processes controlling groundwater geochemistry. The correlation analysis helps in the determination of the spinal and the seasonal species (ions). Calcium (Ca2+), Magnesium (Mg2+), Sodium (Na+), Chloride (Cl−), Bicarbonate (HCO3-) and Sulphate (SO42-) were determined as spinal species and Potassium (K+), Phosphate (PO4-) and Silica (H4SiO4) as the seasonal species. Factor analysis shows that dissolution and leaching of secondary salts, weathering and anthropogenic impacts are the dominant controlling factors in the study area. Though several factors were extracted for different seasons to identify the dominant hydrogeochemical regime of the study area, first three dominant factors were spatially distributed by their factor scores. This spatial representation of the factor scores show that part of the region is hydrogeochemically active.