Bahr el Jebel and Bahr el Ghazal sub-basins are one of the least understood major sub-basins of the Nile and yet the existing hydro-met monitoring network is also very limited. The few available stream flow records exhibit substantial breaks and are of very poor quality
Seasonality the Bahr el Jebel Sub-basin is seen to have a single peak occurring between August and October as opposed to the two seasonal peaks in the upstream part of the Nile Basin. The standard deviation of the monthly flows is also seen to be high as gauged at Mongala partly because of the steeper section with rapids and rock outcrops as flow enters into the sub-basin from the Albert Nile and the various torrential streams entering the Bahr el Jebel (with a single seasonal peak) before the gentle slope.