Blue Nile is the main contributor of Nile flow (65%) at High Aswan Dam. The mean annual flow at one third land cover of Blue Nile in Ethiopia, Kessie station (65784 km2) from the year 1980-2000 is 17.4 BCM. The effective runoff generated by the watershed upstream of the Kessie station is estimated to be 265 mm. For the same duration, the mean annual flow of the Blue Nile at the border station yields 51 BCM with effective runoff of 285 mm. The unimpeded mean annual runoff at Khartoum is estimated at 56 BCM, resulting in an effective runoff of 180mm. But due to abstraction, mainly for irrigation, recorded mean annual inflow of Blue Nile at Khartoum from the year 1980 to 2000  is around 48 BCM. The effective runoff is reduced westward in the sub-basin because of the reduction of rainfall amount. Rahad and Dindir, both originated from the south-western highland plateaus of Ethiopia, are contributing mean annual flow of 4 BCM to the Blue Nile system (ENTRO).


References and further reading:

Conway, D. (2000) The climate and hydrology of the Upper Blue Nile, Ethiopia, Geographical Journal, 166, 49–62.

Camberlin, P. (2009) Nile Basin Climates, The Nile: Origin, Environments, Limnology and Human Use.

NBI (2012) State of the River Nile Basin Report, Nile Basin Initiative (NBI) Publishing, Entebbe, Uganda.

Sutcliffe, J., Parks, Y. P. (1999) The Hydrology of the Nile, IAHS Special Publication no. 5, IAHS Press, Institute of Hydrology, Wallingford, Oxfordshire OX10 8BB, UK, p. 33, and 57–87, 1999.

Wolman, M. G., Giegengack, R. F. (2008) The Nile River: Geology, Hydrology, Hydraulic Society, Large Rivers. John Wiley & Sons, Ltd, 471–490. 

UNEP (2013) Adaptation to Climate-change Induced Water Stress in the Nile Basin: A Vulnerability Assessment Report, Division of Early Warning and Assessment (DEWA), United Nations Environment Programme (UNEP), Nairobi, Kenya.

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