Generally, most of the rainfall stations within the Lake Victoria sub-basin record annual rainfall amounts in excess of 1,000mm with some (in the western part of the sub-basin) going up to as high as 1,600mm. Apart from the noticeable increment in the early 1960s, there is relatively small inter annual variations in rainfall recorded within the basin. This rainfall is a very important component of the Lake Victoria water balance as it is believed to balance evaporation over the lake.