Status and changes of water quality in typical near-city zones of three East African Great Lakes in Tanzania

Abstract

Tanzania is the only country bordering all three transboundary East African Great Lakes, i.e., Lake Victoria, Lake Tanganyika, and Lake Nyasa (Lake Malawi). This study investigated the spatiotemporal variability of basic physicochemical parameters of nearshore surface waters in Mwanza Gulf (Lake Victoria), Kigoma Bay (Lake Tanganyika), and Wissmann Bay (Lake Nyasa). Water quality was evaluated using the water quality index (WQI) method. Results showed that N and P nutrient pollution was relatively severe in central and southern parts of Mwanza Gulf owing to external agricultural emissions and internal release associated with physically disturbed sediment resuspension. External inputs from inflowing surface runoffs from the city of Mwanza typically enhanced N loading in northern parts of the gulf during the rainy season. Poor water quality was found in central and southern parts of Mwanza Gulf, especially in the rainy season. Algal blooms and NH 4 + -N (total P and total N) were the main factors driving water quality degradation in the rainy (dry) season. Kigoma Bay and Wissmann Bay both had good water quality, except in river mouth areas in Lake Nyasa during the rainy season. The degradation in water quality was caused primarily by increased land-based nutrient and turbidity inputs. To respond to challenges associated with climate change and local socioeconomic development, long-term monitoring of the lacustrine environment and systematic limnological studies will be required, not only in the three bays but also more widely throughout the three lakes and their basins.

Citizen scientist monitoring accurately reveals nutrient pollution dynamics in Lake Tanganyika coastal waters

“…Among the five studied sites, Ilagala and Ujiji showed elevated nitrate, total nitrogen, total phosphorus, total suspended solids, and turbidity, while the lowest concentrations were found in Gombe (Table 3 ). Ilagala lies in the lake area influenced by the Malagarasi River, while Ujiji receives effluents from the much smaller Luiche-Ujiji River (Shen et al, 2022 ). Both rivers have been identified as important sources of particulates to Lake Tanganyika (Langenberg et al, 2003 ; Shen et al, 2022 ).…”

“…Ilagala lies in the lake area influenced by the Malagarasi River, while Ujiji receives effluents from the much smaller Luiche-Ujiji River (Shen et al, 2022 ). Both rivers have been identified as important sources of particulates to Lake Tanganyika (Langenberg et al, 2003 ; Shen et al, 2022 ). Turbidity is expected to decrease exponentially with distance from the river mouth in deep lakes (Giovanoli, 1990 ).…”

“…Coastal waters, however, present more complex optical conditions and require more in situ monitoring. These areas are also where the local population are directly impacted by changes in water quality (Shen et al, 2022 ).…”

Integrated Application of SWAT and L-THIA Models for Nonpoint Source Pollution Assessment in Data Scarce Regions

“…Rapid population growth in the past few decades, coupled with the continuous expansion of agricultural and urban land, has put great pressure on the water quality of Lake Victoria [6,7]. Due to the deficiencies in the environmental management systems, untreated emissions from domestic garbage, sewage, agricultural pesticides, and fertilizers have been prevalent in the highly populated areas around the lake, leading to serious eutrophication of Lake Victoria [8,9]. As a result, the ecosystem within the lake and the safety of drinking water in the lake zone have been seriously affected [10][11][12][13].…”

Developing a High-Resolution Seamless Surface Water Extent Time-Series over Lake Victoria by Integrating MODIS and Landsat Data

“…The lake supports more than 30 million people in the three countries (Uganda, Kenya, and Tanzania) around it and modulates the regional climate [1][2][3]. It plays an important role in regional sustainable development and in the protection of the ecological environment [4,5]. In recent years, Lake Victoria has undergone unprecedented changes that have remarkably impacted livelihoods in the region, giving rise to considerable hydrological, ecological, and environmental concerns [6][7][8][9].…”