The objective of this study is to evaluate the spatial variation of borehole water quality with depth, and compare with the Nigerian Standard for Drinking Water Quality (NSDWQ) used in Uyo Municipality. Uyo, the State Capital of Akwa Ibom is in the coastal plain sand formation of Nigeria. Four functioning boreholes located at representative zones of the municipality were selected, and their water samples collected monthly by pumping for one year and analyzed by standard procedures at the

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... ogy laboratory of the State Water Board for physico-chemical and heavy metal properties. Two sampling methods, grab and composite methods, were applied to this study. Heavy metals were oxidized with nitric acid digestion and analyzed by Atomic Absorption Spectrometry (Unicam Model). The result of the laboratory analyses was evaluated against the NSDWQ and the degree of or percent compatibility was computed. The borehole quality was further evaluated using SPSS ver 17 package, descriptive statistics, paired sample t-statistics, ANOVA and correlation coefficient. Significant spatial differences (p< 0.01 and p< 0.05) were observed in the water quality especially for ammonia, calcium hardness, magnesium, barium, DO and SS, with concentrations which were generally above NSDWQ and particularly, similar trends were observed in water qualities of the boreholes with 54.54m and 45.45m depths. The percentage compatibility of the water quality with the standard varied with depths as follows: 63, 64, 71, and 87% for 45.45, 54.54, 60.60 and 106.06 m depths respectively, giving a strong correlation (r = 98%) between the depths of borehole and their water qualities. The water quality compatibility with the standard varied with different borehole depths in the corners of Uyo Urban, Akwa Ibom State, Nigeria. Depth must be considered if quality compatibility has to be guaranteed in the coastal plain sand formation and water quality authority should set a baseline depth range for standard compatibility quality assurance in Uyo Municipality, considering groundwater dynamics and the seepage of polluted runoff in the largely flat terrain of the territory.