Space-time variation of hydrological processes and water resources in Rwanda Focus on the Migina catchment Omar Munyaneza SPACE-TIME VARIATION OF HYDROLOGICAL PROCESSES AND WATER RESOURCES IN RWANDA FOCUS ON THE MIGINA CATCHMENT Space-time variation of hydrological processes and water resources in Rwanda Focus on the Migina catchment DISSERTATION Submitted in fulfillment of the requirements of the Board for Doctorates of Delft University of Technology and of the Academic Board of the UNESCO-IHE Institute for Water Education for the Degree of DOCTOR to be defended in public on Wednesday, 7 May 2014 at 10:00 hours in Delft, the Netherlands by Omar MUNYANEZA Master of Science in Water Resources and Environmental Management, National University of Rwanda (NUR), Butare, Rwanda born in Umutara, Gatsibo District, Rwanda This dissertation has been approved by the promoter: Prof. dr. S. Uhlenbrook Composition of the Doctoral Committee: Chairman Rector Magnificus TU Delft Vice-chairman Rector UNESCO-IHE Prof. dr. S. Uhlenbrook UNESCO-IHE/Delft University of Technology, Promoter Prof. dr. V.G. Jetten Twente University/ITC Prof. K.A. Irvine UNESCO-IHE/Wageningen University Prof. dr. ir. H.H.G. Savenije Delft University of Technology/UNESCO-IHE Prof. dr. ir. U.G. Wali University of Rwanda, Butare, Rwanda Dr. S. Maskey UNESCO-IHE Prof. dr. ir. N.C. van de Giesen Delft University of Technology (reserve member) The research reported in this dissertation has been sponsored by the Government of The Netherlands through UNESCO-IHE, Delft, The Netherlands, and Nuffic/NPT-WREM Project, Butare, Rwanda. CRC Press/Balkema is an imprint of the Taylor & Francis Group, an informa business © 2014, Omar Munyaneza All rights reserved. No part of this publication or the information contained herein may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, by photocopying, recording or otherwise, without written prior permission from the publishers. 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 nor the author for any damage to the property or persons as a result of operation or use of this publication and/or the information contained herein. Published by: CRC Press/Balkema PO Box 447, 2300 AK Leiden, The Netherlands e-mail: [email protected] www.crcpress.com – www.taylorandfrancis.co.uk – www.balkema.nl ISBN: 978-1-138-02657-5 (Taylor & Francis Group) FOREWORD The contribution to a better understanding on hydrological processes in a catchment for water resources planning and management in the region, that is characterized by very high competing demands (domestic vs. agricultural vs. industrial uses) was agreed since I started my PhD research in 2008. This was the time when Prof. Dr. Stefan Uhlenbrook was advertising the two PhD studies available to Rwandan young researchers, who hold Masters in a water related domain. Prof. Dr. Innocent Nhapi, former Manager of UR-WREM Project and Prof. Dr. Umaru G. Wali, the current Dean of the School of Engineering at UR, encouraged me to apply for this opportunity. I didn’t hesitate and immediately applied because the subject was relevant and fitted with my hydrology and water resources background and interest. At that time, I was the Director at the Institute of Scientific and Technological Research (IRST) but I didn’t regret the decision of leaving this position to continue my studies, as my dream was to become a researcher or a teacher with good qualifications. Academic career was my first choice and by chance the PhD in surface water hydrology was given to me after succeeding the interview, later combined with groundwater hydrology after my colleague Miss. Flora Umuhire left. I was asked to join the University of Rwanda (UR), Huye Caampus, which is former National University of Rwanda (NUR). I also accepted and was appointed in the Master’s program of Water Resources and Environmental Management (WREM) as Assistant Lecturer and later promoted to Lecturer grade due to my publications/performance. My challenge was to first improve my knowledge in this domain to be able to teach in this program. The WREM project aims to contribute to poverty alleviation and sustainable socio-economic development in Rwanda by stimulating solution-oriented research related to water resources and environmental management. I have been fully committed to contribute to the achievement of this mission. To contribute to this, my research focused on understanding the water resources of Rwanda and dominant hydrological process interactions in the specific meso-scale Migina catchment (257.4 km2). The catchment has been equipped with hydrological instruments and after installation, rainfall, evaporation, runoff, hydrochemical and isotope data were observed over two years (May 2009 to June 2011). As a junior hydrologist, my challenge was to understand the hydrological processes in the targeted study area before the dominant hydrological process interactions could be assessed. However, due to my limited knowledge of hydrology and also lack of senior hydrologists in the whole country, my promoter Prof. Dr. Stefan Uhlenbrook decided to allocate to me two MSc research students (Harmen Van den Berg and Rutger Bolt from Vrije University of Amsterdam, The Netherlands) and we worked together intensively in this ungauged Migina catchment for four months from April 2009 onwards. In this short period, we have installed 13 rain gauges and three tipping buckets gauges, two evaporation pans, one weather station, five river gauging stations and eleven shallow piezometers for groundwater monitoring. During this time, a number of problems came such as some equipment like divers have stopped working and others were stolen. Beside this, some staff gauges were pushed away by unexpected large floods. Therefore, I had to regularly check and repair the equipments, replace divers with new ones and appoint guards on sites for equipments security. The data collected from this fieldwork and later, up to two years was used to understand the hydrological processes in a catchment. Due to short time series data, the recent collected data were checked for their quality/accuracy using long time series data recoded in and around the catchment before Rwandan genocide of 1994. The Migina catchment was further developed to the water resources and environmental management research site of the National University of Rwanda. I hope and will do my best that the data collection will continue in this area to help the future BSc, MSc and PhD students carrying out their research in water management field and support decision makers for water resources planning and development. vi During the last 5 years, I learned a lot about hydrological processes in a meso-scale catchment and found that cross-disciplinary knowledge and understanding constituted an important element of my individual and professional capabilities. I also gained huge personal experience by spending a lot of time in the field, where I got to know a large variety of people, and made many friends and learned about the importance of observing. I believe this experience will for sure contribute to the development of Rwanda as it has enriched my life and left me with many friends from different countries all over the world where I presented my findings. MSc students from the UR-WREM Programme will benefit from my experience as well as BSc students from Applied Sciences and Agriculture faculties in Rwanda. Omar Munyaneza UNESCO-IHE, Delft, The Netherlands April 2014 ACKNOWLEDGEMENTS This thesis is part of Water Resources and Environmental Management Project of University of Rwanda (WREM-UR) funded by the Netherlands Government through UNESCO-IHE and Nuffic/NPT PhD research fellowship. Additional funds for on-site implementation and data collection was facilitated by the Nile Basin Capacity Building Network Project (NBCBN) and the UR Research Commission facilitated to attend and present the research findings in different conferences. Moreover, I would like to say special thanks to UNESCO-IHE Institute for Water Education for their financial support and nice cooperation, Ms. Jolanda Boots (PhD Fellowship Officer at UNESCO-IHE) was remarkable and is sincerely acknowledged. First of all, I would like to thank my promoter Prof. Dr. Stefan Uhlenbrook for all the constructive discussions and useful advice. Thank you for all the opportunities you gave me and making time in your always busy schedule to discuss my progress and give me helpful and quick feedback. Thanks you for your infinite effort to push and stimulate me to always focus on hydrological sciences. You never stopped to tell me “Omar, always think as a Hydrologist!”. This thesis is the results. I would also like to extend my sincere thanks to my supervisors/mentors from UNESCO-IHE, Dr. Shreedhar Maskey and Dr. Jochen Wenninger for all the help they provided me with and the guidance they kindly gave me during this study. Your significant contribution to this research is highly appreciated. I really admire your consistent encouragement to pursue excellence in every component of this study. I exceedingly benefited from your understanding of hydrological processes and modelling, critical thinking, instrumental set-up and technical writing ability. I am very very grateful for your dedication! Many thanks are due to my local PhD supervisor/mentor from UR, Prof. Dr. Eng. Umaru Garba Wali for his overall