Effect of Land Use Activities on Water Quality and Vegetation Cover Change in Nsooba - Lubigi Wetland System, Kampala City

Abstract

An assessment of the effect of land use activities on water quality and vegetation cover change in Nsooba - Lubingi Wetland System in Kampala city was conducted between July and October 2020. In order to achieve the set objectives, twelve locations were selected from the Nsooba - Lubingi Catchment. The physico-chemical characteristics of water along the catchment area were determined by standard analytical methods. The average values for Total Dissolved Solids across all the land-use types of wetland, built up areas and agriculture were lower than the National Standard (750 mg/l). A similar pattern of the land-use  was observed for the parameters Total phosphorous, Biological oxygen demand, Chemical oxygen demand, Total suspended solids and Total organic carbon, where the observed average values were all below the National Standards of 10 mg/l, 50mg/l, 70mg/l, 50mg/l and 50mg/l, respectively. The Total Nitrogen average value for built-up areas (11.27 mg/l) was higher than the national standard of 10 mg/l while the remaining land use types of wetland (8.05mg/l) and agriculture (5.96mg/l) were below that of the recommended standard. GIS and remote sensing techniques were used to analyze high-resolution satellite imagery captured during 1998, 2008, and 2018. Wetland coverage declined by approximately 5 hectares (47.2% to 14.58%) from 1998 to 2018. Although most of the measured parameters were below the National standard specified by the Uganda National Environmental Management Authority apart from Total Nitrogen for built-up areas, there is need for close monitoring of the water quality in Nsooba - Lubingi catchment to ensure public health safety. The increased built-up environment in the Nsooba - Lubigi wetland affects ecosystems services of the wetland. The buffer zones for flood control and sewage treatment have been turned into a built-up environment. The results from this study suggest a need to protect the Nsooba - Lubingi catchment for its important ecosystems services of flood control and sewage treatment.