International Journal of Applied Science and Technology Vol. 4, No. 4; July 2014 271 A Groundwater Quality Study of Lagos State, Nigeria Soladoye, O. Department of Geography & Planning Lagos State University P.M.B. 1087 Apapa, Lagos Nigeria Ajibade, L.T. Department of Geography & Environmental Management University of Ilorin P.M.B. 1515, Ilorin Nigeria Abstract The paper is aimed at investigating the physico-chemical and microbial quality of water in 30 shallow wells in Lagos State. Results showed that groundwater quality in Lagos is highly variable from one location to the other. Water parameters were found to exceed set local (SON) and international (WHO) standards. Analysis of pH indicated that groundwater in 14 locations are acidic. The 500mg/l WHO limit for TDS was exceeded in 5 locations while EC limit was exceeded in 4. The presence of zinc and Escherichia coli (e.coli) in water samples calls for attention. From the study, there is no sampling point that did not have at least one parameter exceeding set standards. None of the sampling wells can be considered ‘pure’. Therefore, groundwater within the Lagos environment cannot be said to be potable. It is a major concern to users, agencies responsible for water provision and governmental bodies. This paper calls for further research. Keywords: water quality, shallow wells, groundwater, water parameters, water standards, Lagos 1. Introduction Groundwater is fast becoming an essential resource that cannot be ignored in any part of the world (Llamas, 2005). Prior to this recent development, attention was placed on surface water as a component of the hydrological cycle for water supply, particularly in urban areas. In developing countries like Nigeria, groundwater was considered only as a means of rural water supply. Efforts on water supply development were focussed on surface water. However, the situation is changing even on a global scale. According to Gronwall et al, (2010), an estimated 269 million urban dwellers depend on wells as their principal source of drinking water. In urban Nigeria, it is estimated that almost 60 per cent of the population rely on local wells. This rapidly increasing trend seems to be partly due to people’s need to self-supply for lack of alternative sources, and partly due to cheaper well drilling technologies. Many countries are turning to groundwater as a reliable source of supply. This situation has been aggravated by the large-scale pollution of surface water. Also, factors such as the generally wide availability of groundwater, its low capital development, cost and normally excellent natural quality are leading to rapid development of groundwater resources (Foster and Chilton, 1993). Groundwater has unique natural features which make it suitable for public water supply (Offodile, 1983). It has excellent natural quality, usually free from pathogens, color, turbidity, and can be consumed directly without treatment (Jain et al, 1996). However, it has been observed severally in literature that groundwater is losing its natural purity. For instance, the microbiological and physicochemical analyses of borehole water samples from eastern Obolo LGA of Akwa Ibom State, Nigeria were conducted by Itah and Akpan (2005) to ascertain the potability. Some physicochemical parameters like iron and mercury in some boreholes did not meet the WHO standard for potable water.