Modeling for delineation of protection areas for shallow groundwater resources in peri-urban areas.

Abstract: Bwaise III in Kampala, Uganda is a densely populated informal settlement with a shallow groundwater table and inadequate basic services. High risk of groundwater contamination will bring health problem to the local residents. In this study, a large dimension (300 m in length) 2D model was developed to depict the hydrogeological condition and to examine the response to different rainfall infiltration rate on the groundwater table. The boundary condition of the drainage system plays an important role in modeling the groundwater flow. The simulation results show that water in the drain will flow into the aquifer when the drain is full, otherwise the drain will act as a sink for ground water. Advective transport of phosphorus results in no pollutants reaching or percolating into the drain. The integration of phosphorous concentra-tion flowing out of Domain 3 (pollutant inlet) corresponds to the infiltration rate and the plume moves faster during the wet season which brings in more phosphorous compared with the dry season. With sorption, all the phosphorus was adsorbed within the top soil. A simplified 3D model was set up to illustrate the flow field. Additional simulation can be undertaken within this 3D frame for more realistic calculation and consistent prediction.