Global Journal of Earth and Environmental Science

This study presents an integrated hydrogeochemical and microbial assessment of groundwater quality in Uke and its environs, a Basement Complex terrain in North Central Nigeria, where boreholes and hand-dug wells constitute the principal source of domestic water supply. Fifteen groundwater samples, comprising ten boreholes and five hand-dug wells, were collected during the dry season (December) and analysed for physicochemical parameters, major ions, five heavy metals (Fe, Cr, Pb, Hg, As), and the bacteriological indicators Total Coliform and Escherichia coli. Results were evaluated against World Health Organisation (WHO) and Nigerian Standard for Drinking Water Quality (NSDWQ) guidelines. Most physicochemical parameters were within the selected guideline values, although EC, TDS, turbidity, potassium, and pH showed localised departures: EC exceeded 1000 µS/cm at four sites, TDS exceeded 500 mg/L at six sites, turbidity exceeded 5 NTU at four sites, potassium exceeded 10 mg/L at twelve sites, and pH fell below 6.5 at three sites. Piper, Durov, and Schoeller diagrams indicate that groundwater is predominantly of Ca–Mg–HCO₃ type, consistent with silicate weathering and carbonate dissolution within the crystalline aquifer, with a minority of samples showing a Ca–Mg–Cl or Ca–Na–HCO₃ signature suggestive of localised cation exchange; this facies interpretation is indicative rather than definitive, as major-ion charge-balance errors for two-thirds of the samples exceed ±20% in a verified dataset (full sample-by-sample values reported in the main text). Pearson correlation indicated a strong EC–TDS relationship in both borehole (r = 0.998) and hand-dug well (r = 0.997) samples, consistent with dissolved ionic load as a principal control on conductivity. Iron exceeded the guideline at BH5, while lead exceeded the guideline at BH5 and BH6; arsenic remained within or equal to the applicable guideline at all sites, and chromium and mercury were not detected. All computed Heavy Metal Evaluation Index values were below 10, and all Heavy Metal Pollution Index values were below 100, indicating that none of the sampled sources falls in the unsafe heavy-metal pollution category, though BH5 and BH6 are identified as priority sites for confirmation sampling. All 15 groundwater sources contained Total Coliform, and E. coli was detected in 14 of 15 samples, indicating that none of the sampled sources is suitable for direct consumption without treatment; although sampling occurred during the dry season, the persistence of contamination suggests it may be sustained by structural deficiencies, stored contamination, or hydraulic connection with shallow polluted zones rather than seasonal surface infiltration alone. The findings indicate that groundwater in Uke is broadly acceptable on physicochemical grounds but is bacteriologically unsafe for direct consumption, underscoring an urgent need for wellhead protection, water-point rehabilitation, and routine disinfection across the study area.