Water and food security are essential to human survival and well-being vis-a-vis sustainable resources management and attainment of the SDGs. This study employed hydrogeochemical and GIS-based assessments of impacts of land use and urbanization on groundwater with emphasis on the resilience and security of coastal water supply in Lagos metropolis, SW-Nigeria.
For the assessment of land-use changes and associated impacts on community livelihood, Spot 5 satellite imagery of 1984, 2002 and 2017 of Lagos area alongside with Landsat ETM+ and OLI were used to generate the land use / land cover (LULC) changes in ArcGIS 10.3 Software. For the hydrogeochemical quality assessment, seventy (70) water samples were collected from different household water points (wells and boreholes) within Lagos. In-situ physicochemical parameters (pH, Temperature, TDS and EC) were measured in the field followed by laboratory analyses of major cations and anions.
GIS-based assessment revealed a significant increase in the built-up areas from 447.3km2 in 1984 to 951km2 in 2017 representing 85% increase with corresponding loss of about 5% of the forested coastal wetlands. This is a clear indication of rapid urbanization in the last three decades with attendant impacts on coastal water quality and sustainability. Hydrochemical assessment revealed elevated electrical conductivity (EC) of >1,000μS/cm alongside with elevated Na (51-230mg/l), Cl (300-980mg/l) and SO4 (36-88mg/l) concentrations in shallow wells and boreholes tapping the upper unconfined aquifer. This is a clear fingerprint of groundwater vulnerability to saline intrusion and contamination.
Therefore, in the face of reality of impacts of anthropogenic land-use and climate-induced changes, there is the need for a clear governance structure to regulate the rate of groundwater abstraction and indiscriminate groundwater development to ensure sustainable groundwater resources management and attainment of SDG-6 and avoidance of water supply crisis. Such crisis can be avoided, if appropriate knowledge-based choices, planning / management options are employed; failure of which will likely be very costly.