Groundwater Modelling, An Effective Tool in the Assessment of Groundwater Contamination: A Case Study of Umunwanwa in Umuahia-South, Abia State, Nigeria

To determine the environmental suitability (impacts on groundwater) of an excavated pit located within the eastern boundary of Umunwanwa for any form of waste discharge (sewage or solid waste), modelling approach was adopted. A thorough geophysical / hydrogeological investigation carried out in the area revealed the existence of 7 layers and in the vicinity of the site an unsaturated semi-permeable zone with clay lenses. Site specific hydraulic conductivity of 9m/d was determined through grain size analysis. The groundwater flow direction of the area is from south-east to north-west and the flow system consists of two aquifers separated by a 6.1m thick confining layer. The simulation was carried out for short and long term assessment which gave rise to two sample problems. Sample Problem 1: (Upper aquifer) which is the “Modelling of Groundwater Mound Resulting from Effluent Infiltration,” where analytical and numerical models for calculating