Development of Well Water Quality Model for Obudu Metropolis, Southern Nigeria
DOI:
https://doi.org/10.68050/JAMS.2026.713Keywords:
KEYWORDS: groundwater quality; hand-dug wells; seasonal variation; multiple linear regression; Obudu; Cross River StateAbstract
Shallow hand-dug wells are the everyday water source for many households in Obudu, Cross River State, but little is known about how their quality changes through the year or how it relates to the way each well is built and sited. We sampled 50 wells every month from January to August 2022 (400 well-month observations; four dry-season and four rainy-season months) and measured fourteen physicochemical and microbiological parameters, with each well’s depth, lining, cover and distance to the nearest pollution source. About 49% of the 400 pH readings, and 28 of the 50 wells on their eight-month means, were below the 6.5 lower guideline limit; because pH was read with a visual comparator, these figures are semi-quantitative. Nitrate (maximum 46.5 mg/L), TDS and electrical conductivity stayed below guideline values. Turbidity exceeded 5 NTU in 50.5% of rainy-season readings against 5.5% of dry-season readings, and total coliforms (membrane filtration, CFU/100 mL) were detected in 332 of 400 samples. Because each well was measured eight times, we fitted linear mixed-effects models with a random intercept for each well. Rainy-season water had higher turbidity (+44%), TDS, dissolved oxygen, bicarbonate and calcium, and lower nitrate, magnesium, alkalinity and total coliforms (−32%); pH did not change. After Holm correction, unlined wells were more turbid (lined wells −23%, 95% CI −34 to −10%) and uncovered wells carried higher heterotrophic counts (covered wells −12%, −17 to −6%). Between-well differences accounted for 15–85% of the residual variance, so repeated-measures modelling mattered. In leave-wells-out cross-validation, the models explained at most 19% of the variance in new wells (turbidity), and none for pH. The results support well lining and covering, household disinfection and rainy-season monitoring, and show that well-level characteristics alone do not predict quality well enough for use in screening.
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