Abstract

A water table head distribution map of the shallow Benin Formation aquifer in the Effurun-Warri area has been drawn from dug well data and used to define groundwater gradients as well as identify directions of groundwater movement in this densely populated urban setting. Water samples from forty dug wells were also screened for the presence of lead and cadmium and results showed a variation in concentration from not detectable to 0.04mg/l for each metal. Iso-concentration contours for lead in groundwater suggest that enrichment may be from two sources: wastes from the refinery and petrochemical industrial complex on the northwestern edge of the city and secondly from leachates associated with the many unregulated waste dumpsites. Lead appears to be constrained from spreading eastwards from the industrial complex area by the south and westwards trending groundwater gradient. The city wide prevalence of elevated levels of cadmium is also probably due to leachates from unregulated dumpsites as well as the mixing of groundwater as suggested by existing gradients. Potential implications of the findings for public health, local and regional water quality monitoring are discussed.

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