Monthly observed rainfall data was collected mainly from the NBI database which was originally gathered from the member countries, other sources being GHCN, NBE, MWE, and NBRP. The selection of the stations for use in this atlas was
Monthly observed rainfall data was collected mainly from the NBI database which was originally gathered from the member countries, other sources being GHCN, NBE, MWE, and NBRP. The selection of the stations for use in this atlas was based on the length of the records, quality of the data, and the spatial location of the station with an idea to get a fair spatial distribution of the stations across the basin. Most of the data used had been quality controlled by the Nile Basin Initiative Secretariat. Spatially, there is a gradual decrease of rainfall amounts from upstream to downstream with some upstream areas registering up to monthly maximums of 700mm in the rainy seasons (March- May) and the lower arid parts of the basin registering maximums of up to 60mm in the wet season (July – September). There are two distinct wet seasons separated by dry seasons in the equatorial lakes region, which gradually transform into a single wet season, followed by a dry one in the other parts of the basin.
This section of the atlas presents the monthly rainfall distribution over the Nile Basin presented at sub-basin level and clearly indicating the variations in seasons 