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Investigation of the Hydrological Quality of Ethiope River Watershed, Southern Nigeria
Abstract
June and increases steadily reaching its peak in October. The physico-chemical parameters of both water sources include, pH (5.28-7.06), turbidity (1.16 – 8.12 NTU), conductivity (65.00- 127.0 ìs/cm), dissolved oxygen (4.40-7.60 mg/l) and total hardness (25.50 – 45.0 mg/l). Others include, Na+ (3.91 – 27.05 mg/l), K+ (3.91 – 8.73 mg/l), Ca2+ (3.21 – 9.60 mg/l), Mg2+ (1.46- 5.84 mg/l), HCO3
- (31.50-80.00 mg/l), Cl- (17.55 –35.10 mg/l), SO4 2- (0.25-0.58
mg/l), NO3 2- (0.19-0.55 mg/l) and PO4 2- (0.20-19.00 mg/l). This physico-chemical quality is generally compatible with WHO guideline for domestic use. Nevertheless, the water samples consist of high microbial population including total coliform bacteria counts (39.00 – 1100 MPN/100ml) and Escherichia coli (21.00 – 305.00 MPN/100ml), which render both surface and groundwater unfit for domestic use without disinfection. An assessment of surface water-groundwater homogeneity using the parametric student’s t and F tests on selected constituents (chloride, nitrate, sulphate, phosphate, sodium, potassium, calcium and magnesium), indicate non-significance in the
variation within the tested parameters except for nitrate. This suggests some groundwater-surface water intermixing or communication, and the activity of denitrifying bacteria in surface water. A groundwater pollution vulnerability assessment using DRASTIC model indicates moderately high pollution risk level for the aquifer system