Spatial correlation of groundwater pollutants with the vulnerability index in Kano Metropolis, North-western Nigeria

This study performed a correlation analysis between groundwater quality parameters with organic and inorganic pollutants using the area under the curve (AUC) of the receiver operating characteristics (ROC) map in Kano Metropolis, North-western Nigeria. The aim is to present the spatial relationship between groundwater pollutants and the existing vulnerability condition of the groundwater resources with a view to developing a vulnerability risk map. Eight water quality parameters (Ca, Al, Cl, NO3, TH, Mg, TDS which include potassium and sodium) and pH were used to develop the water quality index to represent the general overview of the groundwater pollutants. Vulnerability parameters (depth of water, net recharge, aquifer media and groundwater conferment on sensitivity analysis) were used as reference points for preparing ROC. Inorganic pollutants and hydrocarbons representing organic pollutants were integrated into the analysis process with a view to identifying their influence on the groundwater pollution level in the area. The measured AUC under ROC revealed a positive correlation between groundwater vulnerability with organic (63.7%) and inorganic pollutants (65.6%). Vulnerability risk mapping based on hydrocarbon concentration revealed a high level of pollution risk, especially in the core centre of the metropolitan Kano. HIGHLIGHT Groundwater pollution and vulnerability studies are one of the key issues in water resources management, especially in areas with a high level of risk of groundwater pollution such as metropolitan areas (Kano Metropolis inclusive) with a high rising population.