LAKE VICTORIA BASIN

Rainy day at Lake Bunyonyi in Kabale, Uganda

Rainfall is the primary source of water recharge for the LVB, contributing 80 per cent of the water entering the Lake (Awange et al. 2008). The main water reservoirs in the Basin include surface water in lakes, rivers, streams and wetlands, and groundwater in aquifers. There is considerable variation in the intensity and spatial distribution of rainfall across the Basin. This is demonstrated by the study conducted in Kericho, Kabale and Bukoba (Kizza et al. 2009). The annual precipitation

cycle in Bukoba and Kabale, as much as the rest of the LVB, shows two distinct rainy seasons: the March to May rainy season, and the September to December rainy season. The rainy seasons are punctuated by two dry seasons between January and February, and between June and August (Kizza et al. 2009). The September to December period receives less rainfall than the March to May season. The daily, seasonal and inter-annual variability of LVB’s climate results from the interaction between the inter- tropical convergence zone (ITCZ), El Nino/Southern Oscillation (ENSO), Quasi- biennial Oscillation (QBO), large-scale monsoonal winds, meso-scale circulations and extra-tropical weather systems (Nicholson and Yin 2002). The seasonal north to south movement of the ITCZ results in the two rainfall seasons, while the inter- annual variability in received rainfall corresponds to the ENSO changes (Kizza et al. 2009). The study by Kizza et al. (2009) further indicates an overall increase in the average rainfall amounts in the LVB. There is, however, some variation across the region: while there has been a general increase in the average annual rainfall in the western sections of the Basin, some stations in the eastern section recorded a decline.

Lake Ruhondo in the Kagera sub-basin, Rwanda

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