1st Edition
The Impact of Soil Erosion in the Upper Blue Nile on Downstream Reservoir Sedimentation
Population growth in the Blue Nile Basin has led to fast land-use changes from forest to agricultural land, which resulted in speeding up the soil erosion processes producing highly negative impacts on the local soil fertility and agricultural productivity. The eroded sediment is transported downstream by water and sinks in the lower basin where it significantly reduces reservoir storage and irrigation canals capacity. The only effective solution to mitigate the sedimentation problem is to limit the sediment inputs from upstream by locally implementing erosion control practices. However, given the vastness and remoteness of the involved areas, this first requires the knowledge of the most critical zones.
The book identifies the sources of the sediment depositing in the Lower Blue Nile Basin and quantifies the amounts involved providing essential information for the planning and implementation of any interventions aiming at reducing soil erosion. The methods used consist of extensive field work covering most of the basin, watershed, hydrodynamic and morphodynamic modelling and, for the first time, the mineralogical analysis of the sediment at the sources and sinks. The method is successful in indentifying the areas providing most of the transported sediment, where it is recommended to start with erosion control practices.
1 Introduction
1.1 Background
1.2 Research aims
1.3 The Blue Nile Hydrosolidarity Project
1.4 General methodology
1.5 Structure of the thesis
2 Blue Nile River Basin
2.1 Nile River
2.1.1 White Nile River
2.1.2 Blue Nile River
2.1.3 The Atbara River
2.1.4 The Main Nile River
2.1.5 The Nile Delta
2.2 Blue Nile River and its basin
2.2.1 Location and topography
2.2.2 Climate
2.2.3 Hydrology
2.3 Structures and water extraction for irrigation
2.3.1 Chara Chara Weir and Fincha Dam
2.3.2 Roseires Reservoir
2.3.3 Sennar Reservoir
2.3.4 Proposed Dams
2.3.5 Water extraction
2.4 Sediment transport
2.5 Sedimentation problems in the lower basin
2.5.1 Introduction
2.5.2 Irrigation canals sedimentation
2.5.3 Roseires Reservoir sedimentation
2.5.4 Sennar Reservoir
2.6 Blue Nile Bedform
2.7 Concluding remarks
3 Computations of flow and sediment balances in the Blue Nile river
3.1 Background
3.2 Materials and methods
3.2.1 Data analysis
3.2.2 SWAT model
3.2.3 Model development
3.2.4 Model calibration and validation
3.3 Model application
3.3.1 Results of sensitivity analyses
3.3.2 Results of model calibration and validation
3.3.3 Result of water balance
3.3.4 Assessment of sediment loads
3.4 Land-use change detection
3.4.1 Jemma Sub basin
3.4.2 Didessa Sub basin
3.4.3 South Gojam Sub basin
3.5 Concluding remarks
4 Hydrodynamic characteristics of the Blue Nile River network2
4.1 Background
4.2 Materials and methods
4.2.1 Model input data
4.2.2 Model development
4.2.3 Model calibration and validation
4.3 Assessment of current water distribution
4.4 Concluding remarks
5 Sediment fingerprinting in Roseires Reservoir
5.1 Background
5.2 Sediment sorting inside Roseires Dam
5.2.1 Model description
5.2.2 Hydrodynamic model setup, calibration and validation
5.2.3 Morphodynamic model setup, calibration and validation
5.2.4 Identification of promising coring locations
Location 1
Location 2
5.3 Sediment fingerprinting
5.3.1 Samples collection
5.3.2 X-ray Diffraction (XRP)
5.3.3 Cluster analysis
5.3.4 Mineral content results
5.3.5 Cluster analysis results
5.4 Concluding remarks
6 Morphodynamics impacts of Grand Ethiopian Renaissance Dam and Roseires heightening along Blue Nile River
6.1 Background
6.2 New development
6.2.1 Roseires Dam heightening
6.2.2 Grand Ethiopian Renaissance Dam (GERD)
6.3 Model description
6.3.1 Sobek-River model
6.3.2 DelWAQ model
6.3.3 Numerical solution of the advection-diffusion processes
6.4 Data analysis
6.5 Morphodynamic model
6.5.1 Model setup
6.5.2 Model calibration
6.5.3 Model validation
6.5.4 Impact of new developments
6.6 Concluding remarks
7 Discussion and conclusions
References
Samenvatting
About the Author
Biography
Dr Yasir Ali has considerable experience in many aspects of river engineering gained during 14　years of practice. His main expertise is in river hydraulics and river morphodynamics gained through his involvement in projects dealing with river morphology. Dr Ali played a major role in field investigations and hydrographic surveys throughout his years of involvement in applied research. He gained a strong theoretical background during his M.Sc. study and Ph.D research in the Netherlands. He worked on hydrodynamic modeling for the entire Blue Nile River, from Lake Tana to Khartoum, using the Delft Sobek software. In 2009, Dr Ali conducted a trans-boundary bathymetric survey along the Blue Nile River in both Ethiopia and Sudan, sampling bed levels and suspended sediment. He worked in the Watershed Management Program under the Eastern Nile Model Program (ENMP) in the Eastern Nile Regional and Technical Office (ENTRO), from April 2012-July 2012, Addis Ababa (Ethiopia).
