TUSCIA UNIVERSITY OF VITERBO -ITALY- DEPARTMENT OF TECHNOLOGY, ENGINEERING AND ENVIRONMENT AND FOREST SCIENCES (DAF) PHD IN SCIENCES AND TECHNOLOGIES FOR THE FOREST AND ENVIRONMENTAL MANAGEMENT- XXII CYCLE SCIENTIFIC SECTOR- DISCIPLINARY AGR/10 RURAL CONSTRUCTION AND FORESTRY LAND PhD Thesis Presented by Aziz Abouabdillah HYDROLOGICAL MODELING IN A DATA-POOR MEDITERRANEAN CATCHMENT (MERGUELLIL, TUNISIA). ASSESSING SCENARIOS OF LAND MANAGEMENT AND CLIMATE CHANGE. Coordinator Supervisors Prof. Gianluca Piovesan Dr. Antonio Lo Porto Prof. Nicoletta Ripa 2006-2009 This thesis is submitted in fulfillment of the requirements for the Degree of Doctor of Philosophy. UNIVERSITÀ DEGLI STUDI DELLA TUSCIA -VITERBO- DIPARTIMENTO DI TECNOLOGIE, INGENERIA E SCIENZE DELL‘AMBIENTE E DELLE FORESTE CORSO DI DOTTORATO DI RICERCA IN SCIENZE E TECNOLOGIE PER LA GESTIONE FORESTALE ED AMBIENTALE-XXII CICLO SETTORE SCIENTIFICO-DISCIPLINARE AGR/10 COSTRUZIONE RURALI E TERRITORIO AGROFORESTALE Tesi di Dottorato di Ricerca Dottorando Aziz Abouabdillah HYDROLOGICAL MODELING IN A DATA-POOR MEDITERRANEAN CATCHMENT (MERGUELLIL, TUNISIA). ASSESSING SCENARIOS OF LAND MANAGEMENT AND CLIMATE CHANGE. Cordinatore Tutors Prof. Gianluca Piovesan Dr. Antonio Lo Porto Prof. Nicoletta Ripa 2006-2009 ACKNOWLEDGEMENTS I am greatly indebted to the Water Research Institute (CNR-IRSA) for their financial support through a grant from the European project “Aquastress” I would like to express my profound gratitude to Dr. Antonio Lo Porto for his invaluable contribution through supervision of this PhD research. He had a Paramount input into this research through his guidance from initial proposition to its completion and brought out the best of me. Thank you. There is a person I need to mentioned especially, Dr. Anna Maria De Girolamo, I owe her my sincere gratitude for her kindness, her useful contributions and support at various stages of this work. Thanks also go to Prof. Nicoletta Ripa for her supervision, help and assistance particularly during my stay in Viterbo. To those in the Water Research Institute (IRSA-Bari), I would like to thank with all my heart for making my study so memorable and pleasurable. Thanks also to the Tuscia University of Viterbo (Italy) for the opportunity provided to me to achieve this academic goal. I’d like to convey my heartfelt thanks to Dr. Jeff Arnold, Dr. Mike white and Professor Raghavan Srinivasan for their efforts and assistance, during my PhD training in the Texas A & M University and the ARS-USDA in Temple. I wish also to thank Prof. Wesley Wess Wallender for his scientific support, as well as his kind help and assistance during my PhD training in the University of California Davis. I wish to express my sincere gratitude to the INAT (Institute National Agronomique de Tunis), and in particular to Prof. Lili Zohra Chaabana and Mr. Aymen Lazrek for their significance help and data providing; the IRD (Institut de Recherche et de Development) in particular Dr. Christian Leduc as well as to all other data providers not explicitly mentioned above. I would like to express my most sincere gratitude to Prof. Ahmen Bamouh and Prof, Benasser Alaoui from my home Institute (IAV-Hassan II) for their significant help and encouragement. Thanks also to the examiners who provided valuable feedback, Prof. Roberto Mercurio, Prof. Enrico Marchi, and Prof. Carmelo Riccardo Fichera. I would also like to express my sincere thanks to the numerous colleagues who have supported me along the way. i DEDICATION This thesis is dedicated to My Father who has raised me to be the person I am today. You have been with me every step of the way, through good times and bad. Thank you for all the unconditional love, guidance, and support that you have always given me, and helping me to succeed. Thank you for everything. I love you. My mother, who has been a source of inspiration to me throughout my life. Thanks for your support encouragement, and constant love that have sustained me throughout my life. I love you. My sister Chadia, for her never ending moral support and prayers. Thanks for your love and encouragement, I give my deepest expression of love and appreciation for the encouragement to you and your husband Si'Mohammed. My brother Moulay Ahmed, thanks for your advices and support. I m very proud of your success. I wish to express my sincere gratitude to you and your wife Zineb. My sister Siham, who proffered me unconditional love and support. Thanks to be my friend and my confidant, you have been a great source of inspiration and motivation throughout the years. Thanks Sima. My lovely nephews Ali, Omar, Mehdi and Ghali. The happiness of the family. Thanks for giving me your love and support, and most importantly were often the source of much loved distraction. The Memory of my dear grandmother who passed away during the first months of this thesis. May God bless you Oumi. Ons, for always being here for me. Thank you for your continual love, support, and patience. I could not have made it through without you by my side. Loving thanks to my childhood friends Charif, Hatim, Younes, Noureddine and Mehdi who knowingly and unknowingly- led me to an understanding of some of the more subtle challenges to our ability to thrive important roles. My friends, Yassine, Soufinae, Otman, Meryem,Houda,Taha, Mounia, Hamid, Hind, Youssef, Radhouan, Nadia, Farachichou, Moez, Khaoula. They played such important roles along the journey, as we mutually engaged in making sense of the various challenges we faced and in providing encouragement to each other at those times when it seemed impossible to continue. Thanks for always being there for me. My most sincere appreciation goes to all my friends, at IRSA, without whom these three years would have been insufferable. I especially want to show my gratitude to Rita, Manola, Ramona, Gerardina, Daria, Delia, Valeria, Emanuele, Giuseppe, Domenico, Lorenzo, Carlo, Angelo and Vito. You have all made it a memorable time of my life. Yours sincerely Aziz ii ABSTRACT Title: Hydrological modeling in a data-poor Mediterranean catchment (Merguellil, Tunisia). Assessing scenarios of land management and climate change. In the Mediterranean regions, hydrologic processes are quite specific due to the temporal variability of precipitation characterized by a succession of drought and flash-flood periods. These processes may also have changed due to a range of human activities such as land use changes, dams building, soil and water conservations works. The Merguellil catchment (Central Tunisia) is a typical Mediterranean semi-arid basin which suffers regular water shortage aggravated by current drought. It extends on an area of about 1200 km² upstream of the El Houareb dam which presents its outlet. This semi-arid zone is exposed to a high variability of rainfall in time and space. Annual means vary between 300 mm in the plain and 500 mm in the highest parts. During the recent decades the continuous construction of small and large dams and Soil and Water Conservation Works (SWCW) (ie. Counter ridges) has taken place within the watershed. These practices, that currently cover nearly ¼ of the basin surface, are classified in two categories: the practices on basin slopes constituted essentially by contour ridges (200 Km²) and the practices on the hydrographical network by implantation of small hilly dams draining about 170 Km. These water harvesting systems may intercept runoff at the upstream part of the catchment, thus depriving potential downstream users of their share of the resources. However, little is known about the effect of these water harvesting systems on the water balance components of arid watersheds. In such a vulnerable situation of water resources availability, it can be expected that the impact of climate change will further worsen the situation. The work presented here attempts to simulate the actual water and nutrient balance using the integrated hydrological model ―Soil and Water Assessment Tool‖ (SWAT 2005). The simulation results revealed that evapotranspiration is the major component of the hydrological balance. Hydrological Calibration (1992-1994) and validation (1998) have been carried out referring to daily flow data at the Hafouz and Skhira flow-gauges. The model performance was satisfactory and the Nash-Sutcliffe Efficiency coefficient ranges from 0.6 to 0.7. The model was rather successful in reproducing water flow. However the low sampling frequency and the lack of detailed water quality measurement data did not allow an in-depth iii evaluation of the SWAT performance in predicting nutrient and sediment. Some scenarios were further generated. The first one regards the removal of contour ridges to assess their impact to water and sediment load. The results show that the contour ridges contribute to the retention of high quantity of sediment. These regulations reduce the surface runoff by 32 %. Planting the olive trees between contours could improve its yield. The second scenario consists in the reduction of the applied fertilizers. By reducing 20% in the applied fertilizers no change was detected in the olive yield, while a small change was noted for durum wheat yield‘s (-2%). Whereas a net decrease in nutrient load was observed at the outlet. This reduction ranges, from 3 to 10% for nitrates, from 2.5 to 8% for total nitrogen and from 13 to 16.5 % for total phosphorus. Finally, the SWAT model was used to study the impact of future climate on water resources of this Mediterranean catchment. Future climate scenarios for periods of 2010-2039 and 2070-2099 were generated from the Canadian Global Coupled model (CGCM 3.1) for scenarios A1B, B1, and A2. These CGCMs data were then statistically downscaled to generate future possible local meteorological data of precipitation and temperature in the study area. SWAT model was run first under current climate (1986-2005) and then for the future climate period to analyze the potential impact of climate change on flow, evapotranspiration, and soil moisture across this catchment.