Appraising meteoric-surface-groundwater interaction through analyses of hydrochemical evolution of water resources in the Lower Niger River Basin, Nigeria

Suitable evaluation and monitoring of water resources is pertinent for understanding its hydrogeochemistry. This research, therefore, appraised the hydrogeochemical dynamics, surface water-groundwater interactions with rocks, and meteoric water in the lower Niger River Basin, Nigeria, using geochemical analysis, statistical techniques, and ratio plots respectively. This entailed analyzing 5 rainwater samples and 51 surface water and groundwater samples for physicochemical parameters. Findings from the in-situ tests (pH, Temperature, TDS, EC), all indicated compliance with WHO guidelines except few hand-dug well samples that presented TDS and pH values that suggests pollution. The water facies for surface water and groundwater were shown to comprise 72% of Ca-Mg-HCO₃ water type while the rest is contributed by Ca-Mg-Cl (15%), Na-HCO₃ (9%), and Na-Cl/Na-SO₄ (4%). The Schoeller diagram showed predominant ionic content to be Ca > Na > Mg and HCO₃ > SO₄ > Cl for the surface water while for groundwater the arrangement is Ca > Mg > Na and HCO₃ > SO₄ > Cl revealing a similar source of ionic enrichment for both surface water and groundwater. The Pearson correlation projected strong positive correlations between Na+, Ca²⁺, and Mg²⁺, and between CO₃ ²⁻ and HCO₃⁻ in both surface water and groundwater showing a strong relationship between ions in both water sources. Meteoric water contribution to both surface water and groundwater is not significant, since the concentrations of all ions are < 50% except for CO₃ ²⁻ in groundwater. The saturation indices (SI) and chloro-alkaline indices show that the dissolution of halite, anhydrite, gypsum, and alkali feldspars accounts for the water chemistry while ion exchange predominantly defines the hydrogeochemistry of the groundwater.