LAKE VICTORIA BASIN

Atmospheric and Climatic Conditions

The LVB climate is consistent with that of East Africa. Major climatic features that regulate the Basin include the El Nino Southern Oscillation, the Quasi-biennial Oscillation, the Inter-Tropical Convergence Zone and monsoon winds (Anyah and Semazzi 2004). Together with Lake Malawi and Lake Tanganyika, Lake Victoria has an influence on East Africa’s climate (Song et al. 2004). The humid Congo air mass, which originates in the tropical Congo Rainforest, also affects the LVB climate (Anyah and Semazzi 2004). Despite the sporadic dust-storms and the occasional haze from wood burning, the LVB enjoys a relatively unpolluted atmosphere. Temperature Lake Victoria basin average temperatures reach a maximum of about 28.7° C in February just before the March equinox and reach their lowest in July after the June equinox maximum. Minimum temperatures vary from 14.7 to 18.2° C (Lake Victoria Basin Commission 2007). While there are wide differences between cold season and warm season temperatures, studies by Anyah and Semazzi (2004) show that average temperature in the lake varies only slightly from month to month.

Comparison of temperature records for the period 1950- 2000 and 2001-2005 show that maximum temperatures have increased by an average of 1° C (Lake Victoria Basin Commission 2007). Anyah and Semazzi (2004) noted a significant jump in average temperatures in the basin since the 1990s. Air temperature on the Ugandan side of the lake was 0.5 ° C higher in the 1990s than in the 1960s (Anyah and Semazzi 2004). While the interactions between lake surface temperature and rainfall amounts and distribution are complex, there are indications that higher lake temperatures are associated with increased rainfall, with models predicting that some areas of the LVB could receive double the current average rainfall when lake temperatures rise by 1.5 ° C (Anyah and Semazzi 2004). Such an impact of temperature increase would have significant impacts in shaping the East Africa’s climate. Rainfall Average annual rainfall in the Basin ranges from 400 to 2,736 mm (Kizza et al. 2009). The minimum rainfall amount was recorded at Ngudu while the maximum amount was recorded at Bukoba. Recorded rainfall averages show that received rainfall amounts are higher in the north to north- eastern parts of the basin than the amounts received in the southern portions of the basin (Kizza et al. 2009).

Figure 2.1: Average rainfall trends for Lake Victoria Basin since 1903 Source: Kizza et al. 2009

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