Geochemical processes and multivariate statistical analysis for the assessment of groundwater quality in the Swarnamukhi River basin, Andhra Pradesh, India

With rapid increase of human population, swift growth of industries and intensive irrigation activities, groundwater quality is being increasingly endangered by agricultural chemicals and indiscriminate disposal of urban and industrial wastes. Hence, in water management, assessment of groundwater quality is as important as quantity especially in the arid and semi-arid regions. Evaluation of hydrogeochemical parameters and solute acquisition process controlling water chemical composition was studied by collecting 66 groundwater samples in pre-monsoon and post-monsoon seasons in the Swarnamukhi River basin, Andhra Pradesh, India. Geologically, the study area comprises granite and granitic gneisses, quartzite and alluvium. The total dissolved solids classification reveals that majority of the groundwater samples are desirable for drinking, and all are useful for irrigation purposes. Major ion chemistry reveals the ionic dominance pattern among cations and anions is in the order: Na > Ca > Mg > K and Cl > HCO₃ > NO₃ > SO₄ > CO₃ > F > PO₄ in both the seasons. 85 and 89 % of samples are very hard water in pre- and post-monsoon, respectively which needs softening for domestic uses. 48 and 42 % and 34 and 41 % of the samples of the study area are found having sodium (200 mg/l) and nitrate content (50 mg/l) in pre- and post-monsoon seasons, respectively, more than permissible limits which is not good for human consumption. Natural and anthropogenic sources of the solutes have been categorized with the help of different ionic ratios, plots and correlation matrix. Potential salinity sources include deep saline upcoming and wastewater infiltration. Salinity mapping shows brackish to fresh brackish water predominance in the study area. The plot of major ion in the Piper diagram reveals that majority of samples belongs to mixed type followed by Na–Cl facies. Four principal components were extracted from chemical data to explain the major sources and processes responsible for chemical characteristics of groundwater. It shows that silicate weathering, agricultural runoff (fertilizer input), municipal wastewater infiltration play a vital role in the enrichment of ionic constituents. Average water quality index shows that majority of the samples are good to permissible for drinking purpose. Various irrigation indices show good to permissible use of groundwater in agricultural activities. As per the LSI and RSI values, groundwater of the area is considered very aggressive and substantial corrosion is possible.