Improved Hydrological Understanding of a Semi-Arid Subtropical Transboundary Basin Using Multiple Techniques – The Incomati River Basin Aline Maraci Lopes Saraiva Okello IMPROVED HYDROLOGICAL UNDERSTANDING OF A SEMI-ARID SUBTROPICAL TRANSBOUNDARY BASIN USING MULTIPLE TECHNIQUES – THE INCOMATI RIVER BASIN Aline Maraci Lopes Saraiva Okello Cover page: View of the Sabie River from the Kruger National Park. Photo by Frank Eckardt. IMPROVED HYDROLOGICAL UNDERSTANDING OF A SEMI-ARID SUBTROPICAL TRANSBOUNDARY BASIN USING MULTIPLE TECHNIQUES – THE INCOMATI RIVER BASIN 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 Thursday, 2 May 2019, 15:00 hours in Delft, the Netherlands by Aline Maraci Lopes SARAIVA OKELLO Master of Science in Hydrology and Water Resources, IHE Delft Institute for Water Education, Delft, The Netherlands Born in Maputo, Mozambique This dissertation has been approved by the promotors and copromotor Composition of the Doctoral Committee: Rector Magnificus TU Delft Chairman Rector IHE Delft Vice-Chairman Prof. dr. S. Uhlenbrook IHE Delft / Delft University of Technology, promotor Prof. dr. ir. P. van der Zaag IHE Delft / Delft University of Technology, promotor Dr. I. Masih IHE Delft, copromotor Independent members: Prof. dr. D. Mazvimavi University of Western Cape, South Africa Dr. ir. H. C. Winsemius Delft University of Technology Prof. dr. ir. A. B. K. van Griensven Vrije Universiteit Brussels, Belgium / IHE Delft Prof. dr. M. E. McClain IHE Delft and Delft University of Technology Prof. dr. ir. N.C. van de Giesen Delft University of Technology, reserve member Prof. dr. G.P.W. Jewitt (University of KwaZulu-Natal, South Africa) significantly contributed towards the supervision of this dissertation. This research was conducted under the auspices of the Graduate School for Socio-Economic and Natural Sciences of the Environment (SENSE) CRC Press/Balkema is an imprint of the Taylor & Francis Group, an informa business © 2019, Aline Maraci Lopes Saraiva Okello 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 http://repository.tudelft.nl/ihe 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: 978-0-367-28075-8 Acknowledgments This Ph.D. project was supported by a Ph.D. fellowship grant from Netherlands Ministry of Development Cooperation (DGIS) through the UNESCO-IHE Partnership Research Fund (UPaRF). The study was carried out in the framework of the Research Project “Risk-based operational water management for the Incomati River Basin” (RISKOMAN) project. The Water Resources Commission (WRC) of South Africa, also contributed additional funding, through RISKOMAN-WRC part of the project K5/1935, managed by the University of KwaZulu Natal (UKZN, South Africa). All partners of the RISKOMAN project, IHE Delft (Netherlands), UKZN, Inkomati- Usuthu Catchment Management Agency (IUCMA, formerly ICMA, South Africa), Komati Basin Water Authority (KOBWA, Swaziland), Eduardo Mondlane University (UEM, Mozambique), including the reference group are thanked for their valuable inputs. The financial contribution through research grants from the International Foundation for Science (IFS) Stockholm, Sweden, through a grant (W/5340-1), the L’Oréal- UNESCO "For Women in Science, Sub-Saharan Africa 2013" and Schlumberger Foundation “Faculty of the Future Fellowship 2014-2015” are also highly appreciated. I would like to thank my promoters Prof. Dr. Stefan Uhlenbrook, Prof. Dr. Pieter van der Zaag, Prof. Dr. Graham Jewitt and supervisor Dr. Ilyas Masih for the patience, enthusiastic supervision, guidance, inspiration and encouragement to pursue this PhD. I also remember Prof. Huub Savenije, Prof. Diniz Juizo and Prof. Wim Bastiaanssen (WATPLAN project) for the valuable advice and contributions. It is such a privilege to work with extraordinary scholars like you. The cooperation of the Soil Science Department of UKZN, particularly of Prof. Simon Lorentz and Mr. Cobus has been essential for the success of fieldwork and is gratefully acknowledged. The South African National Parks (SANParks) - Kruger National Park (KNP) is also recognized for allowing fieldwork to take place within the park area. To the staff of KNP, IUCMA and Department of Water and Sanitation (DWS) that helped with fieldwork my special thank you – it was a great and enriching experience for me to be out in the field with you. A special thanks to late vi | Acknowledgments Maduna and the researchers of SANParks – KNP that have assisted with monthly collection of water samples. IHE-Delft laboratory staff is also thanked for assistance with analysis of isotopes, cations and anions. Streamflow, climate and water quality data was kindly provided by the Department of Water and Sanitation (DWS) in South Africa, South African Weather Service (SAWS) and UKZN. Staff from Ara-Sul DGUBI is also acknowledged for data provided for Mozambican locations, as well as assistance with water sampling. I would like to acknowledge the support and guidance of my colleagues at UKZN; Eddie Riddell, Tinisha, Mercy and many other students for their suggestions, discussions, and support during fieldwork. I appreciate a lot the support from various staff members of UKZN in gathering data and taking care of logistics. My appreciation also goes to the PhD colleagues at IHE Delft (former UNESCO-IHE) for the valuable ideas. The constructive comments of anonymous reviewers and editors from journals where several chapters of this PhD were published are greatly appreciated. My heartfelt appreciation to several friends that helped me in various ways. Micah for countless advice regarding coding and modelling as well as Caroline, Veronica, Patricia, Chris, Pedi, Raquel, Vivian, and all the students that worked on Incomati/Riskoman project. The various staff members of IHE-Delft that always ensured we had pleasant and productive times in Delft. And to the Mozambican and Kenyan communities in Delft, who were my home away from home in the Netherlands. Cloverley, my accountability ‘buddy’ for the last 3 years, really helped me to keep motivated and enthusiastic about my work; a big thank you also to Olga, from Productivity for Scientists. The ladies Bible Study group in Richards Bay (South Africa), especially Wendy and Sue, have prayed countless times regarding my PhD and related issues. I really appreciate your friendship and fellowship. The connect group in Richards Bay, Richards Bay Community Church (RBCC) and Mount Zion International Parish (MZIP, Delft) communities, pastors, and prayer groups are also thanked for their support through the years. Finally yet importantly, I would like to thank my dearest husband Nick for all support, encouragement, and patience. I could have never made it this far without Acknowledgments | vii his unconditional love and affection, protection and provision. To my daughters Zawadi, Priscilla and Nicole for surviving many days without mommy close by, and for going in several trips because of mommy’s PhD. To my dear mother for the amazing support to my family while I was away, my siblings Melanie and Marcel, and for my entire family and friends in Mozambique and Kenya. All glory and honour to God! To my family and all the brave women in this world! Summary Water scarcity is a major issue in today's agenda. For sub-Saharan Africa in particular, dramatic water shortages are predicted in the coming years. Effective water management is crucial for better use of available water resources. Understanding the hydrology of a catchment is important in order to support optimal use of water resources in the face of socio-economic and environmental constraints and uncertainties. In heavily committed river basins such as the Incomati, with many different water use(r)s located in different riparian countries (South Africa, Swaziland and Mozambique), strong interdependencies exist. Water allocation decisions thus have important economic, social, environmental and political consequences. In this case, water allocation decision-making involves difficult trade-offs, for which decision- support tools exist that are frequently based on optimising an economic objective function subject to constraints representing, among other things, hydrological processes. Large variability of rainfall, both within and between years, leads to even larger variations in river flow and adds uncertainty to the water allocation equation. This research project aims at improving understanding of hydrological processes of a river basin, particularly runoff generation processes, to enable better water management. Several tools and approaches were used to achieve this aim. Comprehensive statistical and trend analyses of rainfall and streamflow were conducted, and the Indicators of Hydrological Alteration (IHA) tool was used to describe the streamflow