Groundwater quality evaluation using water quality index and geospatial techniques in parts of Anantapur District, Andhra Pradesh, South India

The main aim of this research is to evaluate the quality of groundwater in parts of Anantapur district, Andhra Pradesh, for drinking and irrigation purposes. Groundwater samples were collected from various locations in the study area during the post-monsoon season and were analyzed for different parameters including pH, EC, TDS, Ca²⁺, Mg²⁺, Na⁺, K⁺, HCO₃⁻, Cl⁻, SO₄²⁻, and NO₃⁻. The results were then compared with the water quality standards of the World Health Organization (WHO). The major ions were found in the following order: Na⁺ > Ca²⁺ > Mg²⁺ > K⁺ = HCO₃⁻ > SO₄²⁻ > Cl⁻ > NO₃⁻. The obtained data was then mapped using the Arc-GIS technique to show the spatial distribution pattern of physicochemical properties and major ion concentrations in groundwater. The water quality index showed that 69% of the samples are very poor, and 31% are unfit for drinking purposes due to effective leaching of ions, over-exploitation of groundwater, direct discharge of effluents, and agricultural impact. Based on the Gibbs diagram, the groundwater samples fall within the rock dominance region. The majority of the samples fell into the C3S1 category, which denotes water with high salinity and low sodium which is moderately suitable for irrigation purposes, according to the USSL diagram. According to the Wilcox classification, 27% and 2% of groundwater samples are deemed doubtful and unsuitable, respectively, while 69% of samples are deemed suitable for farming. In addition, most groundwater samples show moderate suitability for irrigation when evaluated for SAR, %Na, PI, RSC, MAR, and KR. Most of the samples, with the exception of a few spots, turned out to be suitable for irrigation. However, due to human activity, some samples had levels of contamination that were higher than allowed and needed to be treated before consumption.