Hydroclimatology of the Nile: results from a regional climate model

Y. A. Mohamed (1) , B. J. J. M. van den Hurk (2) , H. H. G. Savenije (1, 3) , W. G. M. Bastiaanssen (4)

1 UNESCO-IHE
2 KNMI - Royal Netherlands Meteorological Institute
3 TU Delft - Delft University of Technology
4 ITC (currently with WaterWatch)

This paper is the result of the first regional coupled climatic and hydrologic model of the Nile. For the first time the interaction between the climatic processes and the hydrological processes on the land surface have been fully coupled. The hydrological model is driven by the rainfall and the energy available for evaporation generated in the climate model, and the runoff generated in the catchment is again routed over the wetlands of the Nile to supply moisture for atmospheric feedback. The results obtained are surprisingly accurate given the extremely low runoff coefficients in the catchment.

The paper presents model results over the sub-basins: Blue Nile, White Nile, Atbara river and the Main Nile for the period 1995 to 2000, but focuses on the Sudd swamp. Limitations in both the observational data and the model are discussed. It is concluded that the model provides a sound representation of the regional water cycle over the Nile. The model is used to describe the regional water cycle in the Nile basin in terms of atmospheric fluxes, land surface fluxes and land surface-climate feedbacks. The monthly moisture recycling ratio (i.e. locally generated/total precipitation) over the Nile varies between 8 and 14%, with an annual mean of 11%, which implies that 89% of the Nile water resources originates from outside the basin physical boundaries. The monthly precipitation efficiency varies between 12 and 53%, and the annual mean is 28%. The mean annual result of the Nile regional water cycle is compared to that of the Amazon and the Mississippi basins.

Domaines: Interfaces continentales, environnement; Océan, Atmosphère; Sciences de la Terre

Y. A. Mohamed, B. J. J. M. van den Hurk, H. H. G. Savenije, W. G. M. Bastiaanssen. Hydroclimatology of the Nile: results from a regional climate model. Hydrology and Earth System Sciences Discussions, 2005, 2 (1), pp.319-364. ⟨hal-00298628⟩