Detection and attribution of changes in river flow and sediment loads in the Nile basin

Abstract

Abstract The Nile basin is the second largest basin in Africa and one of the regions experiencing high climatic diversity with variability and deteriorating water resources. As climate change is affecting most of the hydroclimatic variables across the world, this study assesses whether historical changes in river flow and sediment loads in the Nile basin may be attributed to climatic change. An impact attribution approach is employed by forcing a process-based model with a set of observational and counterfactual climate data for 69 years (1951–2019), from the impact attribution setup of the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP3a). The nonparametric Mann–Kendall test is used to identify trends while long-term mean annual river flow and sediment load simulation differences between a model setup with observational and counterfactual climate data are calculated to allow for quantification of the climate change attribution. Results show a reasonable evidence of a long-term historical increase in river flows and sediment loads of the upper part of the Nile basin, largely attributed to changes in climate. Contrary, there is less impact of climate change on the river flows and sediment loads in the Eastern and downstream parts of the Nile basin. These findings show spatial differences in the sensitivity of impacts of climate on river flows and sediment loads while highlighting the most impacted region in the basin.