Generally, the spatial distribution of rainfall across the sub-basin is fairly reasonable with most areas receiving amounts of over 1,000mm but there is noticeable inter-annual variation. Specifically, areas in the Ethiopian part of the sub-basin receive more rainfall amounts as opposed to those in South Sudan and in the northern part of Uganda.
This basin is strongly similar to that of the Sudd. This means that variations in the climate leading to changes in inflow from the Baro and Pibor, will lead to variations in spill to the Machar Marches. In turn this would lead to variations in the area of the Marches and the effect on the outflow of the basin will be dampened. This makes the outflow of this sub-basin also relatively insensitive to changes in rainfall.