2-Reem-Phd Thesis-Draft-21-2020-04-17-Final W
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Optimizing the Operation of a Multiple Reservoir System in the Eastern Nile Basin Considering Water and Sediment Fluxes Reem Fikri Mohamed Osman Digna OPTIMIZING THE OPERATION OF A MULTIPLE RESERVOIR SYSTEM IN THE EASTERN NILE BASIN CONSIDERING WATER AND SEDIMENT FLUXES Reem Fikri Mohamed Osman Digna OPTIMIZING THE OPERATION OF A MULTIPLE RESERVOIR SYSTEM IN THE EASTERN NILE BASIN CONSIDERING WATER AND SEDIMENT FLUXES DISSERTATION Submitted in fulfillment of the requirements of the Board for Doctorates of Delft University of Technology and of the Academic Board of the IHE Delft Institute for Water Education for the Degree of DOCTOR to be defended in public on Tuesday 26 May 2020, at 15:00 hours in Delft, the Netherlands by Reem Fikri Mohamed Osman DIGNA Master of Science in Water Resources Engineering, University of Khartoum born in Khartoum, Sudan iii This dissertation has been approved by the promotors: Prof.dr.ir. P. van der Zaag IHE Delft / TU Delft Prof.dr. S. Uhlenbrook IHE Delft / TU Delft and copromotor Dr. Y. A. Mohamed IHE Delft Composition of the doctoral committee: Rector Magnificus TU Delft Chairman Rector IHE Delft Vice-Chairman Prof. dr.ir. P. van der Zaag IHE Delft / TU Delft, promotor Prof. dr. S. Uhlenbrook IHE Delft / TU Delft, promotor Dr. Y. Mohamed IHE Delft, copromotor Independent members: Prof.dr. D. P. Solomatine IHE Delft / TU Delft Prof.dr. G.P.W. Jewitt IHE Delft / University of Kwazulu-Natal, South Africa Prof.dr. E. Van Beek University of Twente Prof.dr. S. Hamad NBI, Uganda Prof.dr. M.J. Franca TU Delft, reserve member This research was conducted under the auspices of the SENSE Research School for Socio-Economic and Natural Sciences of the Environment CRC Press/Balkema is an imprint of the Taylor & Francis Group, an informa business © 2020, Reem Fikri Mohamed Osman Digna Although all care is taken to ensure integrity and the quality of this publication and the information herein, no responsibility is assumed by the publishers, the author nor IHE Delft for any damage to the property or persons as a result of operation or use of this publication and/or the information contained herein. A pdf version of this work will be made available as Open Access via https://ihedelftrepository.contentdm.oclc.org/ This version is licensed under the Creative Commons Attribution-Non Commercial 4.0 International License, http://creativecommons.org/licenses/by-nc/4.0/ Published by: CRC Press/Balkema Schipholweg 107C, 2316 XC, Leiden, the Netherlands [email protected] www.crcpress.com – www.taylorandfrancis.com ISBN 978-0-367-56441-4 ACKNOWLEDGEMENTS First and foremost, I praise Allah for helping me to complete this study. I am sincerely grateful to the high quality of supervision given by Prof. Stefan Uhlenbrook, Prof. Pieter van der Zaag and Prof. Yasir Mohamed. Prof. Stefan, I appreciate your continuous support you have given me during my PhD journey. Prof. Pieter, I am very grateful for your in-depth comments which shaped my study to reach the current product. Prof. Yasir, thank you for providing me the Doctoral training opportunity. I am grateful to the Netherlands Fellowship Programme (NFP) for funding this research. I would like to thank Jolanda Boots from IHE Delft for her support in all administrative work. I record my deep gratitude to Silvia for supporting me when I was ill. I consider myself fortunate indeed to have the opportunity to pursue my study at IHE, an institute with a multi-cultural environment. I had a chance to meet good and inspiring people from all over the world, to exchange knowledge and expand my network. I thank friends from the IHE PhD group, Chol Abel, Mawiti Infantri Yekti, Yasir Salih, Zahra Naankwat Musa, and Mario Castro Gama, for sharing thoughts and experience. My deep sense of thanks to my good friends and accommodation mates, Eiman Fadol, Jakia Akter and Marmar Badr, I was blessed by your accompany during my stay in Delft. I cannot forget the blessed accompany of Shaza Jameel, Salman Adam, Omer Musa, and Sara Altayeb. My thanks extend to the Sudanese Community in Netherlands in general and Delft, Ghada, Tayseer, and Eng. ALfatih family, for providing sense and warmth of home. Special thanks to Mr. Fikri Kurror, the first person I met in Netherlands. This acknowledgement would not be completed without mentioning my friends from Sudan, Nazik, Nayla and Zeinab, I owe deep sense of gratitude to your accompany and encouragement which helped me a lot to continue my journey. Nayla, thank you for sharing your thoughts and rich experience. Nazik, I appreciate your care. Zeinab, I have been gifted by meeting you for the first time at IHE and having your rock steady support. I owe my deepest gratitude to my family, both extended and small. My parents, without your encouragements and unconditional support I would never come to what I have done. There are no proper words to convey and express my gratitude for your wisdom. My brothers, Mohamed, Mazin and Mutaz, thank you for all what you did and I cannot even tell. Mazin, can’t forget your effort to facilitate model computations in coputers of limited capacities. My small family, spouse Masoud and children, Lana, Ahmed, Mohamed and Momin, I am immeasurably grateful for your patience and sacrificing when I was away from home. v Acknowledgement I cannot end my acknowledgement without thanking the soul of my uncle Hassan Shalabi Mukhtar, a teacher who fought for Nubian’s female education. His love and encouragement for education is behind the success of many women in Sudan. vi 1 SUMMARY The Eastern Nile (EN) riparian countries Egypt, Ethiopia and Sudan are currently developing several reservoir projects to contribute to the needs for energy and food production in the region. The Nile Basin, particularly the Eastern Nile Sub-basin, is considered one of the international river systems with potential conflicts between riparian countries. Yet, the Eastern Nile is characterized by the high dependency of downstream countries on river water generated in upstream countries. In the absence of formal mechanisms for collaboration, the transboundary nature of the EN basin makes sound water resources development very challenging. The large seasonal and inter-annual variability of the river flow exacerbate those challenges. A further complication is the high sediment load in the EN Rivers, particularly during the high flow season. The operation of most of the reservoirs have been developed without sufficiently considering sediment management. The Nile basin water resources have been extensively studied during the last 100 years or more, for planning and management purposes, in particular with regard to the use of irrigation water in the downstream part of the basin, though recently some studies have also focused on use of water for hydropower generation in the upper parts. These studies show that there is no convergence of development plans emerging among the Nile riparian countries. Another challenge is that the current reservoir optimization and simulation models cannot handle the temporal and spatial variations and implications of sediment deposition of multiple multi-purpose reservoirs. The aim of this PhD research is to analyse the long-term impacts of water resources development on water quantity and reservoir sedimentation, considering different system management options and operating rules of existing dams. To identify knowledge gaps regarding modelling of Nile water resources, the first part of this PhD research reviewed water resource models applied in the Nile Basin, distinguishing between simulation, optimization and combined simulation and optimization models. The review shows that the political dimensions and societal, economic and environmental risks associated with water resources development have not been fully addressed in the Nile basin models, which could possibly explain why certain developments are opposed by some riparian countries. The output of this part was important to guide future research on water resources planning and management in the Nile. The second part of the PhD study investigated the implications of water resources development on water availability in the Eastern Nile basin, for hydropower generation and irrigation water demands. The implications were assessed both at country and regional levels, using scenario analysis within a river basin simulation model. Twelve scenarios were investigated including: new dam developments; new irrigation schemes; vii 1. Summary and different options for dam operation, i.e. unilateral versus cooperative transboundary management of dams. A RIBASIM model of the Eastern Nile was built that included twenty dams and twenty-one irrigation schemes, and used historical data of the hydrology of 103 years at a monthly time step as input. The operating rules of existing dams were assumed to remain unchanged. Four indicators were used for evaluating the performance of the system: hydropower generation [MWh/yr], reliability of irrigation supply [%], reservoir net evaporation [106 m3/yr] and flow regimes of rivers [m3/s]. The third part of the PhD study aimed to analyse the optimal operation scenarios for water resources management in the EN to satisfy hydropower generation and irrigation requirements. A hydro-economic optimization model based on Genetic Algorithm and a deterministic optimization approach was developed and used to determine the maximum benefits for two scenarios: (i) non-cooperative management of dams in the EN basin by the riparian countries, and (ii) cooperative management of those dams among the riparian countries. The EN system was optimized in the cooperative management scenario as one system and generates system-wide economic returns. In the non-cooperative management scenario, the system within each country was optimized separately, releases from the optimal system state in the upstream country were used as regulated inflows for optimizing the downstream country’s system. The simulation results of current operation of the existing system were used as base scenario to compare the results of optimization.