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Moisture recycling over the Nile basin
Y. A. MOHAMED1,2, B. J. J. M. VAN DEN HURK3 & H. H. G. SAVENIJE4
1 UNESCO-IHE, PO Box 3015, 2601 DA Delft, The Netherlands
2 IWMI NBEA, PO Box 5689, Addis Ababa, Ethiopia
3 KNMI, PO Box 201, 3730 AE De Bilt, The Netherlands
4 Delft University of Technology, 2628 CN Delft, The Netherlands
Abstract At river basin scale, water resources system analysis should consider all components of the regional water cycle. Measurements and numerical experiments in hydroclimatology have confirmed both positive and negative land surface–climate feedbacks, of which moisture recycling is a prominent phenomenon at continental scales. Applying Budyko’s model, the mean annual moisture recycling over the Nile has been computed as 11%. The general characteristics of moisture recycling over the Nile have been compared to that of the Amazon and the Mississippi. Given the prognostic limitation of the recycling ratio, a regional climate model has been applied to simulate the two-way (land surface–atmosphere) interactions over the Nile Basin. The model has been used to evaluate the impact of draining the Sudd wetlands on the Nile regional hydroclimatology. The results from two model simulations are compared: the present climatology and a drained wetlands scenario. It is found that draining the wetlands has negligible impact on the regional water cycle, but a large and significant impact on the local climate.
Key words evaporation; moisture recycling; Nile basin; regional climate model