A GIS-based DRASTIC and GOD models for assessing alterites aquifer of three experimental watersheds in Foumban (Western-Cameroon)

Abstract

Groundwater contamination and vulnerability in urbanised areas are of major concern and require greater attention. In Cameroon, as in most developing African countries, people in urban and peri-urban areas do not have easy access to pipe-borne water. The vast majority of the people have groundwater as main source of water supply. The main objective of this work is to study shallow aquifers in the Foumban locality by applying the DRASTIC and GOD models coupled with the Multivariate Statistical Analysis in order to efficiently assess the vulnerability of these aquifers. This locality is located in a crystalline and crystallophyllian basement zone where two types of aquifers are developed namely: the subsurface and the fractured aquifers. To that effect, the Depth to water table, Recharge, lithology of the Aquifer, Soil media, Topography, vadose zone and the hydraulic Conductivity were prepared, classified, weighed, and integrated in a Geographic Information System. Based on the DRASTIC model, the result showed that the study area is weak and moderately vulnerable. With regard to the GOD method, vulnerability maps indicated three levels of vulnerability index to pollution: inconsiderable, low and moderate vulnerability. For both methods, areas lying mainly between “weak vulnerability” and “moderate vulnerability” categories extend along the three experimental watersheds in the study area. The sensitivity analysis and the multivariate statistical tests show that the depth to water table and the impact of vadose zone were the most significant parameters in the vulnerability assessment. The modelling results were approved by comparing them with nitrate concentration in the groundwater. Among all analysed samples, the borehole F401 has nitrate concentrations that exceed the WHO standard for the water intended for human consumption. According to this study, the groundwater vulnerability maps provide important preliminary information which could greatly help in the protection of local water resources.