Mapping Groundwater Vulnerability and Risk of hydro-carbon Contamination in a Semi-Arid Region

Groundwater is a scarce yet vital resource in many arid and semi-arid regions of the world. where it serves as water supply for a majority of the population. The quality of this resource is depreciating, however due to pollution levels reaching intolerable limits as a result of unplanned urbanization and industrialization. In this study, the capabilities of two commonly used groundwater vulnerability models, DRASTIC and GOD, are assessed for correctly classifying the risk of hydrocarbon pollution within the city of Kano, located in semi-arid northern Nigeria. Most existing groundwater vulnerability assessment tools have been developed for use in Europe and North America under generally humid conditions; conversely, vulnerability assessment of groundwater in arid and semi-arid is much less developed.
 Combined analysis of large-scale existing data sources on hydro-meteorological, environmental and anthropogenic factors will be used to evaluate the vulnerability of groundwater resources in Kano, a city of ~4 million people within 137 square kilometres.  In this study, the two models (DRASTIC and GOD) are assessed based on data provided by Nigerian water resources administrations and obtained via field monitoring to detect areas that are vulnerable to groundwater contamination based on the hydrogeological structure and local sources of hydrocarbon contamination. Several groundwater contamination sources have been identified such as automobile shops, household dumpsites, and petrol dispensing stations.Mapping of environmental factors was conducted within the framework of Geographical information systems (GIS), and  preliminary results show a range of very high to moderate vulnerability classes exist within the build-up areas of Kano. A sensitivity evaluation of the various parameters required for each of these models has also been performed to identify the controlling parameters within this semi-arid environment. Building on these results, the next phase of this research will focus on development of a modified vulnerability model based on these identified controlling parameters and model validation using field observations.