Appraisal of groundwater suitability for drinking and irrigation utilities in the Cooum River basin, South India: Implications from uranium, nitrate, and fluoride health risks

Abstract

The study reveals that 6% of groundwater samples exceed the WHO's recommended fluoride limit of 1.5 mg/L, and 15% surpass the nitrate standard of 45 mg/L, rendering the water unsuitable for drinking. Gibbs plot analysis identifies evaporation as the dominant factor affecting groundwater chemistry, while the Piper diagram classifies the water into mixed Ca–Mg–Cl and NaCl types, indicating natural processes and potential seawater intrusion. Cation exchange processes are observed in 75.5% of samples, as shown by Schoeller's indices. The hydrochemical facies evolution suggests freshening from recharge in most samples, with signs of salinity intrusion in others. Between 2010 and 2023, land use and land cover (LULC) changes show a significant increase in built-up areas, resulting in reduced groundwater recharge and heightened pollution risks. The classification accuracy is high, with an overall accuracy of 82.20% and a Kappa coefficient of 83.06%. Water Quality Index (WQI) assessment reveals that 47% of the groundwater samples are excellent for drinking, while 20.6% are suitable. Although 80% of the groundwater remains appropriate for agriculture, the study highlights the need for targeted groundwater management to address urbanization impacts and mitigate health risks from elevated nitrate ingestion, particularly for vulnerable populations such as children.