Identification of the main attribute of river flow temporal variations in the Nile Basin
C. Onyutha1,2 and P. Willems1,31Hydraulics Laboratory, KU Leuven, Kasteelpark Arenberg 40, 3001 Heverlee, Belgium 2Faculty of Technoscience, Muni University, P.O. Box 725, Arua, Uganda 3Department of Hydrology and Hydraulic Engineering, Vrije Universiteit Brussel, Pleinlaan 2, 1050 Elsene, Brussel, Belgium
Received: 02 Nov 2015 – Accepted for review: 09 Nov 2015 – Discussion started: 20 Nov 2015
Abstract. Temporal variation of monthly flows was investigated at 18 Discharge Measurement Stations (DMS) within the Nile Basin in Africa. The DMS were grouped using a clustering procedure based on the similarity in the flow variation patterns. The co-variation of the rainfall and flow was assessed in each group. To investigate the possible change in catchment behavior, which may interfere with the flow–rainfall relationship, three rainfall–runoff models were applied to the major catchment in each group based on the data time period falling within 1940–2003. The co-occurrence of the changes in the observed and simulated overland flow was examined using the cumulative rank difference (CRD) technique and the quantile perturbation method (QPM). Two groups of the DMS were obtained. Group 1 comprises the DMS from the equatorial region and/or South Sudan, while those in Sudan, Ethiopia and Egypt form group 2. In the selected catchment of each group, the patterns of changes in terms of the CRD sub-trends and QPM anomalies for both the observed and simulated flows were in a close agreement. These results indicate that change in catchment behavior due to anthropogenic influence in the Nile basin over the selected time period was minimal. Thus, the overall rainfall–runoff generation processes of the catchments were not impacted upon in a significant way. The temporal flow variations could be attributed mainly to the rainfall variations.
Onyutha, C. and Willems, P.: Identification of the main attribute of river flow temporal variations in the Nile Basin, Hydrol. Earth Syst. Sci. Discuss., 12, 12167-12214, doi:10.5194/hessd-12-12167-2015, 2015.