This study examined the effect of seasonal variation on the physio-chemical and microbial properties of drinking water around slum settlement within Lagos Metropolis. Water samples were collected from different boreholes at different slums around the settlement comprising Group A (Majidun), Group B (Oworoshoki), Group C (Bariga), Group D (Iwaya) and Group E (Ijora Badia) for wet and dry seasons. Parameters of temperature, TDS, pH, hardness, EC, nitrate, sulphate, chloride, E. coli and faecal streptococci are analyzed using standard methods. The obtained data were analysed using SPSS for Windows. Result of the analyses showed that all the parameters have higher concentration during the dry season than in the wet season in all the Groups. Paired sample t-test results revealed that temperature, chloride and sulphate showed no significant variation in all the Groups. Mean values for chloride, hardness, E. coli and faecal streptococci are higher than the WHO guideline provisions. The study concludes that seasonality significantly influences the quality of drinking water in the slums, the water are more polluted during the dry season and recommended that it must be adequately treated if it is to be used for drinking.
Key Words: Seasonal variation, Groundwater, Slum settlements, Pollution, Drinking water quality