Hydrogeochemical Controls and Water Quality Dynamics of the River Kali, Southwestern India

ABSTRACT The relationships among temporal and spatial variations in the hydrogeochemistry of a tropical river in southwestern India were explored to identify catchment-scale processes. River Kali was sampled between 2018 and 2019 to characterise dissolved solute chemistry and water quality. The results indicate that dissolved solute concentration exhibits significant spatiotemporal variability, predominantly influenced by lithology and runoff dynamics. Furthermore, geochemical evaluation suggests that chemical weathering is the principal source of dissolved solutes, with hydrological dilution during high-flow periods and evaporative concentration during low-flow periods modulating this source. The dissolved solute concentrations in the midstream were consistently higher than those in the upstream and downstream regions, primarily due to inputs from industrial effluents. This is evident in the poor water quality indices observed in the midstream, while in most other locations, the indices remain within the permissible limits for irrigation. The mean elemental concentrations in the River Kali are higher than those reported for other rivers draining the southwestern region of the Western Ghats. This study provides insights into the hydrogeochemical dynamics and the evaluation of water resources within a tropical river system.