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Nigeria, Osun State, Ilesha

Effects of waste dumps on groundwater quality in Ilesha and its environs

The study area covers Ilesha and its environs in Osun State, south-western Nigeria. It is defined by latitudes 7°31' to 7° 44' N and longitudes 4° 37' to 4° 51'E and falls within 1:100,000 Sheet 243 Ilesha and covers an area of 625km2.\r\n\r\nThe objective of the project area is to study the hydrogeological characteristics of the area and the impact of waste dumps on the water quality.\r\n\r\nThe methods adopted were geological mapping, geophysical studies, hydrogeological mapping and laboratory analyses of water and soil samples.\r\n\r\nThe rock types in the area in order of abundance are mica schist, quartzite/quartz schist and granite gneiss within these rocks are intrusions of pegmatite and quartz veins.\r\n\r\nThere are peculiar wells that were dry during raining season and have water during the dry season. The clayey nature of the overburden was adduced to have caused delayed recharge of the aquifer due to the low permeability of the overburden materials.\r\n\r\nThe results showed that the waste dumps in the project area have affected the water quality. This is induced by the high nitrate content, high coliform counts and high proportions of trace elements like Iron (Fe), Copper (Cu), Chromium (Cr), Lead (Pb), Nickel (Ni), Cadmium (Cd) and Arsenic (As) which have values that exceed the World Health Organization (W.H.O.) recommended limits. All these are indicators that both the surface and ground waters in the area are polluted (contaminated).\r\n\r\nThe concerned authorities should as a matter of urgency embark on the supply of potable water to the people of Ilesha and environs.\r\n

Inserted in the reports are the following maps (1:50,000): Location & Drainage map, Geological map, and Wet & Dry Seasons Water Elevation Contour maps.