Jeenu Jose^1,2 and A. Krishnakumar^1*

Abstract

Groundwater resources within river basins are gaining global attention due to their critical role in sustaining human and agricultural needs. Preserving groundwater quality is essential for agricultural productivity and public health, as it serves as the primary source of drinking and irrigation water for billions of people worldwide. This study focuses on the hydrochemical characterisation and quality evaluation of groundwater in the lower urbanized regions of the Kallada River Basin (LKRB), covering Kollam town and its surrounding areas. This study aimed to assess water quality for drinking and irrigation purposes while also evaluating the underlying hydrogeochemical processes. The major cations and anions in groundwater follow the order: Ca2+ > Na+ > Mg2+ > K+ and HCO – > Cl- > SO 2-. The dominant groundwater type is Ca-HCO, followed by Na-Cl. The Water Quality Index (WQI) was employed to evaluate groundwater suitability for drinking. WQI analysis revealed that 80% of samples fell within the ‘good to excellent’ range, indicating suitability for drinking and domestic use, while 20% were classified as poor quality. Several indices, such as the Magnesium Hazard (MH), Sodium Adsorption Ratio (SAR), Residual Sodium Carbonate (RSC), Sodium Percentage (Na%), and Kelley’s Ratio (KR), were used to assess the suitability of groundwater for irrigation. The findings indicate that although most samples are safe for irrigation, a few areas have problems with their water quality that render them harmful. This study helps with the sustainable management of groundwater resources in the LKRB by providing important insights for policymakers and urban planners.

Keywords: Groundwater Chemistry, Hydro-chemical Facies, Drinking Suitability, Irrigation Suitability, Water Quality Index, Lower Kallada River