SPATIAL AND TEMPORAL VARIATIONS OF GROUNDWATER QUALITY IN ABEOKUTA CITY, NIGERIA

The quest for safe drinking-water is very high in the ongoing period of environmental pollution. Generally, anthropogenic activities resulting from increasing population and urbanization are major sources of pollution to groundwater. This paper assesses the variation in groundwater distribution in Abeokuta city, Ogun State, Nigeria to determine the water quality status. Secondary groundwater quality data across a period of fifteen years (2001 – 2015) were retrieved from the database of the Department of Water Resources Management and Agro-meteorology, Federal University of Agriculture, Abeokuta, Nigeria to establish the status and examine the spatial and temporal variation. The data was subjected to statistical and geo-statistical analysis. Results showed that temperature, pH and electrical conductivity have a dominant range of 28.0 – 29.9 ºC, 7.01 – 7.50 and 201 – 600 µS/cm, respectively. The major cations Ca2+, Mg2+, Na+ and K+ have respective dominant concentration range from below detection limit (bdl) – 80mg/L, bdl – 30mg/L, 11 – 20 mg/L and bdl – 10 mg/L, while the major anions Cl-, HCO3-, NO3- and SO42- have respective dominant concentration range of 11 – 30, 101 – 200, 1.60 – 4.00 and bdl – 10 mg/L. High (> 1000 µS/cm) conductivity values are detected in parts of the city, which may be due to high concentrations of magnesium, calcium, potassium, chloride and bicarbonate. Only few parts (5.7%) of the city have poor water quality status, while groundwater quality in about 45.7% and 48.6 % of the city may be classified as good and excellent water quality, respectively. The spatial trend showed that groundwater in the core townships of Abeokuta such as Itoku and the environs should not be encouraged for direct consumption without prior treatment. But generally, the groundwater in most part of Abeokuta metropolis is safe for domestic use, though requires some form of household treatment before drinking.