Tekeze Atbaba, like the Blue Nile, has its boundaries spanning from Ethiopia, Eritrea and down to Sudan and also receives highly spatially variable rainfall amounts. The upstream parts of the sub-basin receive mean annual rainfall amounts in excess of 800mm and some areas in Sudan receive less than 300mm with high inter-annual variation of these amounts across the years considered.
The entire Atbara sub-basin is quite large. It covers an estimated 166,875km2. The average annual precipitation over the area is 553mm, the lowest among the Nile sub-basins. The relatively high value of more than 1,300mm of annual rainfall over the Ethiopian Highlands decreases to less than 90mm downstream at the junction of the Atbara River with the Main Nile.