Assessment of Kampala City Groundwater Vulnerability and Possible Management of the Natural Resource

Abstract

Most of the water supply systems in African mega-cities are based on groundwater which becomes a significant source of water. However, unplanned urban expansion and rapid population growth in urban areas have put enormous pressure on this natural resource, which eventually becomes polluted. UNESCO IHP Sanctioned a Consultancy Services for assessment of the Vulnerability to pollution of groundwater resources of Kampala City with the view to producing a technical report and key messages to be used for awareness raising at all levels in order to reduce the contamination within the aquifer. The report and maps are based on field observations, available hydrogeological, geological, hydrochemical and related data and information as compiled and analysed within an ARCView v3.2 and ARCGIS v9.2© GIS. The output of the assessment indicated that the principal water sources in the study area are springs discharging from weathered metasedimentary rocks comprising primarily quartzites and phyllites of the Buganda-Toro formation and complex groundwater flowpaths arise in sub- horizontal layers of fractured quartzite and in the unconsolidated weathered phyllite. 92% of the water sources in the study area are unfit for drinking with respect to bacteriological quality and 33% have unacceptable total iron level. However, groundwater is still a viable option to safe water supply in the study area upon improvement on the sanitary conditions around the source because there is a time lag between precipitation and recharge to the aquifers due to low hydraulic property of the confining layers as evidenced by infinitesimal proportion of recharge during rapid surface and near-surface flows transporting faecal pathogens during heavy rainfall events exceeding 20mm.day".