Mechanisms controlling major ion chemistry and its suitability for irrigation of Narmada River, India

Surface water chemistry of the upper Narmada River was investigated at 13 different locations for four consecutive years (2017–2020) during pre- and post-monsoon seasons. The main objective of the study was to identify the processes governing the water chemistry of Narmada River and evaluate its suitability for irrigation. The physical parameters estimated were; pH (7.9 ± 0.4 for pre- and 8 ± 0.4 for post-monsoon seasons), EC (322.8±93.3 μS/cm for pre- and 312.1±80.2 μS/cm for post-monsoon) and TDS (203.4±41.5 mg/L for pre-and 213.4±48 mg/L for post-monsoon). The obtained concentration of cations and anions were in the order of Ca++ > Na+ > Mg++> K+ and HCO3−> Cl−>SO4−> NO3−> PO4− respectively. Thus, the water of Narmada was found to be alkaline in nature. Piper diagram inferred that the water was dominated by Ca-Mg-HCO3− type of hydrochemical facies. Gibb's plot clarified that rock-water interaction regulates the ion chemistry of the Narmada. Various indices like sodium percentage (Na%), sodium absorption ration (SAR), Kelly index (Ki), permeability index (PI), magnesium hazard (MH) was calculated which showed that the surface water was suitable for irrigation. Lastly, one-way ANOVA (p < 0.05) confirmed no significant differences in water quality except for temperature, EC and SO4−, for pre- and post-monsoon season. HIGHLIGHTS The dominant cation and anion was Ca++ and HCO3− in the Narmada River.; Surface water is characterized as alkaline in nature.; Carbonate and silicate weathering influence the hydrochemistry of Narmada River.; Na%, SAR, Ki, PI, and MH supports surface water suitable for irrigation.; Novel study of the Narmada River.;