Groundwater quality assessment using integrated water quality indices and multivariate statistics in the Upper Bhavani River Basin, India

Groundwater plays a vital role in sustaining human health, agricultural productivity, and ecological balance, particularly in semi-arid regions, making its assessment crucial for the safe and sustainable use. This study assesses the groundwater quality of the Upper Bhavani River Basin, part of the Attappadi Critical Zone Observatory (CZO), using groundwater samples collected across three seasons: pre-monsoon, monsoon, and post-monsoon seasons. The results show that most water samples are suitable for irrigation. Hydrochemical parameters, irrigation suitability indices (SAR, Na%, MH, RSC, KI, and PS), and spatial mapping were employed to assess the groundwater’s suitability for irrigation in the study area. The Irrigation Water Quality Index (IWQI), calculated for both open wells and borewells, shows that open well water is generally good for irrigation, while around 45% of borewell samples are of poorer quality for irrigation purposes. Spatial variation maps of IWQI indicate that comparatively poor water quality is observed in the central region of the study area. Multivariate statistical analyses indicate that geogenic processes are the dominant factors influencing groundwater chemistry, with additional impacts from anthropogenic activities such as agriculture and settlement expansion. The Drinking Water Quality Index suggests that most samples are suitable for human consumption. However, elevated solute concentrations, moderate to high hardness, and mild alkalinity may pose potential concerns for both drinking and irrigation. These findings underscore the need for targeted monitoring, regulated groundwater extraction, and integrated water management strategies to ensure long-term sustainability of groundwater resources in the basin. The findings provide valuable insights that can guide water treatment practices, shape policy decisions, and support future research, ultimately contributing to the development of safer and more sustainable groundwater management strategies for the region.