Inefficient management of landfills and dumpsites for waste disposal is a major problem in Nigeria. Leachates and pollutants from these dumpsites have been known to contribute to the pollution of groundwater systems. The extents of pollution however are poorly quantified since the flow of pollutants continues below earth surface. The use of GIS mapping enabled the evaluation of spatial characteristic of pollutants in the groundwater systems. Thirty (30) hand dug well within 10 – 100m were sampled around two poorly managed dumpsites in Ibadan. Twenty-three (23) physico-chemical and heavy metals water quality indicators were analyzed following Standard Methods. The result were subjected toT- test of mean compared with WHO (2005) drinking water standard (p<0.05). Using GIS Inverse Distance Weighted Interpolation, the maps of the pollutants were produced and the spatial distribution shown. Elevation, topography and slope were major determinants in the distribution of level of pollutant revealed in the generated maps. Although, pH Cl–, K+, Fe, Cr and Pb were not significantly different from the Maximum Allowable Limits (MAL) TSS, TDS, Total Hardness, NO3– , SO42-, Ca, Mg, Na, Cu, Zn, are all lower while CO32-, Mn, Cd, and BOD5 are higher than MAL. The DO is good since it’s averagely higher than minimum required for water drinking. The GIS maps will guide in groundwater prospecting in the area and aid decision on enforcement of environmental standard in siting of residences and groundwater wells.
Key Words: Groundwater, Leachates, Pollution, GIS maps, Ibadan