Geochemical evaluation of groundwater quality in Yewa for drinking and irrigation purposes

Abstract Groundwater quality evaluation is essential for water resource conservation and protection. This study evaluated groundwater quality in Yewa for drinking and irrigation purposes. Fifty well-water samples from five communities were analysed for major ions, pH, and total dissolved solids (TDS). Physicochemical analysis revealed neutral pH (6.97 ± 0.08–7.02 ± 0.09) and low TDS (176.90 ± 75.14 mg/L–441.90 ± 225.08 mg/L), indicating generally fresh water. However, magnesium concentrations (31.80 ± 5.29–81.80 ± 10.08 mg/L) exceeded the Standard Organization of Nigeria limit (20 mg/L). Dietary intake analysis revealed negligible (< 5%) nutritional contributions for sodium, potassium, and chloride, except for Ca (22.4–25.5% RDA) and Mg (72–76% RDA in Ojaodan) in adult males. Mg exceeded tolerable upper intake levels for children aged 1–3 years (Ilaro) and 1–8 years (Ojaodan). The water quality index (32.44–166.64) classified samples as 40% “excellent,” 32% “good,” and 28% “poor,” indicating majority are good for direct consumption. Majority of the irrigation indices (SAR, RSC, KR, PS, %Na, SSP, BH) showed excellent quality, but a high magnesium adsorption ratio (> 50% in 44% of samples), corrosivity ratio (38%), and permeability index (42%) posed a major limitation to long-term soil permeability. Geochemical facies (Piper, Chadha, Durov, Gaillardet, and Gibbs diagrams, etc.) revealed a Ca–Mg–HCO₃ dominant type, controlled by rock-water interaction, reverse ion-exchange, and mixed carbonate–silicate weathering. Principal component analysis (PC1–PC4: 66.82%) revealed that groundwater chemistry in Yewa is primarily governed by the following: (1) shallow weathering coupled with water-level fluctuations, (2) depth-controlled mineralisation, (3) redox-controlled or localised mineral dissolution, and (4) potassium feldspar weathering.