Assessment Of Seasonal Variations In Groundwater Quality And Its Suitability For Agricultural Use In Keffi, North-Central Nigeria

Abstract

Groundwater within the Basement Complex terrain of Keffi and its environs was assessed for seasonal variation, quality for domestic and agricultural uses. A total of sixty-three groundwater samples were collected during wet and dry seasons, and major ion constituents were analyzed. Results showed that values of the analyzed parameters during the wet and dry seasons are within WHO permissible limit, except for NO₃^-. Major cation constituents during both seasons occur in order Ca²⁺ > Na⁺ > Mg²⁺ > K⁺. In the wet season, major anions present in the groundwater occur in the order NO₃^- > HCO₃^- > Cl^- > SO₄^2-, while in the dry season it is NO₃^- > Cl^- > SO₄^2- > HCO₃^-. These major ions are released into the groundwater system owing to the rock-water interaction during weathering of the host rock. The study showed that groundwater in the area is of good to excellent quality, and hence suitable for domestic use as illustrated by the water quality index (WQI) model adopted in this study during both seasons. In terms of the agricultural indices (total hardness, TH; sodium percentage, %Na; sodium absorption ratio SAR; magnesium hazard, MH; residual sodium carbonate, RSC; permeability index, PI) evaluated in both seasons, groundwater is suitable for agricultural use. Bivariate analysis suggests that during the wet and dry seasons, anthropogenic sources contribute to the excess NO₃^- in the groundwater through the application of fertilizer and pesticide, improper disposal of refuse, and indiscriminate open defecation over time.