Effect of land use activities on water quality, soil and vegetation cover for the conservation of nsooba lubigi drainage system, Kampala City

Abstract

Human activities such as agriculture, rural-urban development, industrialization as well as excessive deforestation cause land-use changes associated with water pollution and consequently degradation of the natural vegetation and soil resource. This study, thus, sought to assess the impact of such land use activities on water quality, soil and vegetation cover on Nsooba Lubigi drainage system. The study used quantitative research design where the physical-chemical characteristics of soil and water samples along the catchment area were determined by American Public Health Association standard analytical methods. The actual effect of human activities on land use and vegetation coverage was assessed using image acquisition and processing using GIS. A minimum of 48 water samples and 48 soil samples were collected from designated locations within Nsooba Lubigi drainage system and stored in Duran bottles, ready for analysis. Kruskal-Wallis H-test, Fisher's exact test and ANOVA F-test were applied to analyze the obtained data. Results showed that the parameters differed significantly by stream (p < 0.05). The parameter concentrations of land-use types of wetland, built up areas and agriculture were EC (537.5 μs/cm, 472.5 μs/cm and 272.50 μs/cm), TDS(309.00 mg/I, 352.00 mg/I and 155.00 mg/I), TP (0 .84mg/l, 0.82 mg/I and 0.53 mg/I), TN (8.05mg/l, 11.27 mg/I and5.96mg/l), BOD (5.75 mg/I, 14.00 mg/I and 8.75 mg/I), COD (41.00 mg/I, 49.50mg/I and 42.00 mg/I), TSS (25.00 mg/I, 42.00 mg/I and 10.00 mg/I) and TOC (16.70 mg/I, 20.50 mg/I and 5.65 mg/I). E coli and Total Coliforms concentrations for wetland, built up areas and agriculture were 317.50 CFU/ml, 384.00 CFU/ml and 586.50 CFU/ml; and 912.00 CFU/ml, 1481.00 CFU/ml and 1265.00 CFU/ml respectively. Lead and Cadmium values for wetland, built up areas and agriculture for were 0.614 mg/kg, 0.356 mg/kg and 0.495 mg/kg; and 0.002 mg/kg, 0.005 mg/kg and 0.003 mg/kg respectively. Wetland coverage declined by approximately 5 hectares (47.2% to 14.58%) whereas bare land declined from 14.5% in 1998 down to 7% by 2018. Land-use activity had a significant effect on land cover area with built-up area observed to be higher than area under agriculture and bare land. In conclusion, this study identified human activities as the main drivers for decline in water quality, soil quality and vegetation cover change within Nsooba Lubigi drainage system. This calls for urgent attention by responsible authorities such as NEMA, KCCA and sensitization of surrounding communities on the benefits of this catchment area.