OPTIMUM UTILIZATION of GROUND WATER in KOBO VALLEY, EASTERN AMHARA, ETHIOPIA a Thesis Presented to the Faculty of the Graduate
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OPTIMUM UTILIZATION OF GROUND WATER IN KOBO VALLEY, EASTERN AMHARA, ETHIOPIA A Thesis Presented to the Faculty of the Graduate School of Cornell University in the Partial Fulfillment of the Requirements for the Degree of Master of Professional Studies (MPS) By Abrham Melesse Endalamaw August 2009 ABSTRACT Shortage of precipitation in Kobo valley limits the production of vegetables during dry periods and the yield of cereals in the rainy periods. Irrigation from ground water could enable farmers to cultivate more than once a year. Since pumping has an effect on the ground water resources availability, effective management of water resources using reliable calculation of historical groundwater balances at local and sub- watershed scales is required (Kendy et al 2004). We used CropWat 4 Window to determine PET of the area and the Crop Water Requirement (CWR) of onion, tomato and pepper, which are cultivated using irrigation during dry months; T-M and simple water balance equations were used to quantify annual recharge to the water table and water table status under different irrigation scenarios. Although irrigation from the groundwater could ensure the food security of the area, different water management scenarios showed that the ground water table will be declining as a result. Recharge and water table calculations show that irrigation increases the recharge to the water table but at the same time reduces the overall water table depth due to pumping. Water table depth will not be depleted if irrigation follows the CWR of vegetables. Calculations for future water table levels indicate that, if the current irrigation rate is extended across all of the irrigable land in the area, the water table level will fall by 2 m per year. To protect against further water table decline, flashfloods should be captured and used to recharge to the ground water. KEY Words: Recharge, water table, ground water balance, irrigation, crop water requirement, Kobo Girana Valley Development Project, Kobo, Ethiopia BIOGRAPHICAL SKETCH The author was born at Woldia town, North Wollo Zone of the Amhara Regional State on February 23, 1983. He attended his elementary and junior secondary education at Sanka elementary and junior secondary school. After completion of elementary and junior secondary education, he attended high school at Woldia Senior Secondary. The after a successful completion his high school study, he joined Arba Minch Water Technology Institute, currently named as Arba Minch University, in 2000/2001. He joined the department of Meteorology Science and graduated with a B.Sc degree in Meteorology science in 2005. Right after graduation in 2005, he began working at Arba Minch University as a Graduate Assistant from 2005 to 2007 and as an Assistant Lecturer from 2007 to the start of this study. The author was working in different management positions in the department of Meteorology in addition to teaching. He has research experience in the fields of meteorology, hydrology and agriculture in his future career. The impact of climate change on water resource and agricultural production is of the main interest of the author. He is interested to continue his PhD study as fast as possible in water resource topics. iii “This work is dedicated to my family, friends and who loved me. Special dedication goes to my mother Ertibam Alemu” iv ACKNOWLEDGEMENTS First I would like to thank Cornell University, Bahir Dar University and IWMI’s C19 for the financial support during this work. I also thank Professor Tammo S. Steenhuis who provided me with invaluable ideas and advice over the course of this research. I thank Dr. Amy S. Collick, who was the one that made this work successful by providing all she had to share with me. I would also like to thank Ato Adinew Abate, Manager of KGVDP, who arranged for my access to facilities and written documents in the KGVDP office, in addition to his advice. Special thanks is also due to Girma Takele, Abera Getinet, Midgam Adinew, Esmael Sied, Yeshi, Menbere Belay, Merso, Hussien, Nejib, Desalegn, Wondewosen and all the other workers in the project office for their assistance providing information and helping me during my field visits. Great appreciation and special thanks is given to Ato Biota Derebe, one of the farmers in the study area, who helped me during my field interviews. He worked with me constantly in the field without any payment. v I also thank Ato Daniel G/Hiwot, Tadesse Alemayehu, Wondifraw Getnet, Mengistu Abate, Anteneh Zewde and others, who are my friends and staff members of the university. They provided moral support and helped edit the whole script of this work. At last I thank Jesus, Lord of Kings, who protected me from danger from the beginning to the end of this work, and who is always ready to help me whenever I face difficulties. Many thanks to my father Melesse Endalamaw, my mother Ertiban Alemu, my sisters Alemash Melesse and Destamariam Melesse, and my other family members who gave me moral support, and were dedicated to this work from the beginning to its end. vi TABLE OF CONTENT BIOGRAPHICAL SKETCH ......................................................................................... iii ACKNOWLEDGEMENTS ........................................................................................... v TABLE OF CONTENT ............................................................................................... vii LIST OF FIGURES ........................................................................................................ x LIST OF TABLES ...................................................................................................... xiii LIST OF ABBREVIATIONS ...................................................................................... xv CHAPTER ONE ............................................................................................................. 1 1. Introduction ............................................................................................................. 1 CHAPTER TWO ............................................................................................................ 4 2. Literature review ..................................................................................................... 4 Evapotranspiration ...................................................................................................... 4 Effect of irrigation on crop production ....................................................................... 6 Ground water recharge and discharge ........................................................................ 6 Crop water use and growth stage ................................................................................ 8 Crop water requirement .............................................................................................. 8 Irrigation requirement of the crop ............................................................................... 9 Crop growing period ................................................................................................... 9 Crop coefficient (Kc) ................................................................................................ 11 Available water capacity ........................................................................................... 11 Effective rainfall ....................................................................................................... 12 Methods of water distribution ................................................................................... 13 Irrigation scheduling ................................................................................................. 13 vii Effect of irrigation on ground water table ................................................................ 14 Plant water stress ...................................................................................................... 16 CHAPTER THREE ...................................................................................................... 18 3. The Study Area ..................................................................................................... 18 CHAPTER FOUR ........................................................................................................ 20 4. Data and methods .................................................................................................. 20 Data ........................................................................................................................... 20 Methods .................................................................................................................... 21 Assumptions .............................................................................................................. 27 CHAPTER FIVE .......................................................................................................... 28 5. Result and Discussion ........................................................................................... 28 Potential evapotranspiration ..................................................................................... 28 Growing pattern of the area ...................................................................................... 29 Irrigation and Field water balance under different management scenarios .............. 30 Ground water recharge from rainfall and irrigation .................................................. 37 Effect of Irrigation with CWR of different crop water requirements on ground