Lake Victoria Basin
The eastern part of the basin especially in highlands of Tarime, the rainfall is distinctively bimodal. In the south portion in Mwanza Region, the pattern is unimodal with a wet and dry season. The western part receives rainfall almost throughout the year with minimum in July.There are considerable variations in the average yearly rainfall over the Lake surface and the surrounding land area. Over the extreme eastern area of the Lake, rainfall is between 500 and 750 mm per year. Westward from this area rainfall increase to an annual average of over 2,000mm in areas around Bukoba and the Ssese Islands south of the town. To the south of the lake, in Mwanza Region the yearly average rainfall is 750 to 1100 mm and in the eastern part in Mara Region rainfall is between 750-1000mm increasing to 1600 on the highland areas of Tarime.
The main rivers draining into the Lake include Kagera, Simiyu, Mbarageti, Grumet, Mara and Mori Rivers.
The Lake is shared between Uganda, Kenya and Tanzania.
The most important feature of this basin is the Lake Victoria which is the largest in Africa and source of the White Nile. Lake Victoria lies across the equator between latitudes 0 31N and 3 54S, longitudes 31 18E to 34 54E with an average depth of 80m.