Browsing by Author "Swilla, Livingstone"

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Characterizing Hydrological-Sensitive Areas of The Kinyerezi River SubCatchments in Dar Es Salaam, Tanzania Using The Topographic Index Approach.
(IWA Publishing, 2023) Swilla, Livingstone; Katambara, Zacharia; Lingwandaa, Mwajuma
Several areas experience frequent floods due to anthropogenic activities. Among them, is the Dar es Salaam city, which experiences frequent floods along the Msimbazi River, whose flows originate from different tributaries including the Kinyerezi River. This study aims to evaluate the hydrological-sensitive areas of the Kinyerezi River sub-catchments using topographic index values (λ*) that enable the identification of areas with a higher probability of generating surface runoff. A digital elevation model was utilized to delineate the Kinyerezi River sub-catchment characteristics using ArcGIS 10.4. Soil infiltration rates (Ks) on selected open places were determined using a Guelph permeameter. Soil particle size distributions were analyzed and the λ* values were evaluated. The results showed the particle size distribution contains sand and silt-clay ranging from 46 to 84% and 16 to 53%, respectively. The Ks ranged from 0.6 to 7.8 mm/h while the sub-catchment KS3 scored the highest λ* value of about 10.7. Hence, there is a higher probability for generating surface runoff. Sub-catchment KS16 scored the smallest λ* value of 5.7, perceived to generate less surface runoff. Low-impact development practices capable of capturing runoff and enabling infiltration, evaporation, and detention should be employed in sub-catchments with higher λ* values.
Multivariate analysis of land use/land cover (LULC) effects on water quality in the Lower Mara River catchment
(IWA Publishing, 2026-03-27) Alphayo, Stephano. M; Katambara, Zacharia; Swilla, Livingstone
The Lower Mara River catchment is increasingly subjected to anthropogenic pressure due to land-use/land-cover (LULC) changes, which significantly influence river water quality. This study assessed the effects of LULC on water quality in the Lower Mara River catchment. Water samples were collected from 12 sampling stations during February, August, and December 2025 and analysed for nine physicochemical and biological parameters. Land use/land cover classification was conducted using satellite imagery and GIS techniques, while Pearson correlation and Redundancy Analysis (RDA) were used to evaluate relationships between LULC and water quality parameters within 500, 1,000 and 1,500 m river buffer zones. The results showed that grassland was the dominant land cover type (63.63%), followed by cropland (17.76%) and forest (11.42%). Turbidity, biochemical oxygen demand (BOD5) and faecal coliform concentrations exceeded Tanzania’s standards at several sampling locations, indicating water quality degradation. Pearson correlation and RDA revealed that cropland and built-up areas were significantly positively associated (p < 0.01) with turbidity, nutrients, BOD5, and faecal coliforms, while forests, wetlands, and grasslands contributed to improved water quality conditions. The strongest LULC influence occurred within the 500 m riparian buffer zone. The study emphasises the significance of sustainable management and protection of the river ecosystems.
Quantifying Suitable Low-Impact Development Practices in Mitigating Runoff Floods for the Kinyerezi River Catchment in Dar Es Salaam, Tanzania.
(IWA Publishing, 2024) Swilla, Livingstone; Katambara, Zacharia; Lingwandaa, Mwajuma
As cities expand, changes in land use increase the runoff quantities. Impermeable catchment areas contribute to peak flows, causing floods in insufficiently capacity river reaches. The rate of urbanization witnessed in the Kinyerezi River catchment in Dar es Salaam has contributed to floods in the Msimbazi River. The low-impact development (LID) practices that include bioreten tion (BR) ponds, rain barrels (RBs), rain gardens (RGs), vegetative swales (VSs), constructed wetlands (CWs), etc., can be utilized to mitigate a portion of the surface runoff. This study aims to quantify the suitable LID practices for the Kinyerezi River catch ment in mitigating a portion of runoff floods. The sub-catchment physical characteristics and soil infiltration rates (Ks) were matched with each LID sitting requirements and later by multi-criteria decision-making (MCDM). The results on matching sub-catchment characteristics and LID sitting requirements indicated that BRs, RBs, VSs, RGs, and CWs were the preferable LIDs while MCDM analysis indicated the BRs, RGs, and RBs more appropriate. The BRs, RGs, and RBs were quantified to be 101, 3,698, and 3,698, respectively, within the catchment. BRs are recommended for catchment use while RBs and RGs are recommended for residential buildings. The RBs have the advantage of promoting water-demanding economic activities.