Groundwater vulnerability assessment in Yenagoa,Niger Delta Area, Nigeria
Willabo Miepamo and Andy Bisong Etta
Department of Science Laboratory Technology,Federal Polytechnic Ekowe, NIgeria
This study on aquifer vulnerability assessment in certain parts of Yenagoa, Bayelsa State, Nigeria, adopted the use of DRASTIC method based on geographic information system (GIS)model to delineate areas susceptible to pollution. Seven hydrogeologic parameters were applied for the aquifer vulnerability evaluation which include depth to water table, net recharge, soil media, impact to vadoze zone, aquifer media, topography, and hydraulic conductivity. Data relating to the seven hydrogeologic parameters of the model were obtained and transformed in the model into seven maps by GIS to develop the DRASTIC vulnerability map which shows the three different forms of aquifer vulnerability namely high, moderate, and low zones. The communities within the high vulnerable zones include Swali, Agudama, Ovum, Igbogene, Okutukutu, Onopa and Okolobiri. Those within the moderate vulnerability zones are Kpansia, Etegwe, Yenezue, Azikoro, Opolo, Tombia, Biogbolo and Akenfa and in the low vulnerability zones, we have Amarata, Yenezuegene, Edepie, Azikoro, Akenfa and Okaka.The high vulnerability zones ranking was attributed to very high depth to water table, high net recharge, high hydraulic conductivity and permeability of gravelly sand in the aquifer media. The moderate vulnerability zones was due to high net recharge, low porosity of silt/clay in vadoze zone, siltyloam in soil media and high hydraulic conducitvity. The low vulnerable zones was influenced by impermeability of clayloam in the soil media, low porosity of siltyclay in the vadoze zone and low topographic slope percent.