Rainwater harvesting for dryland agriculture in the Rift Valley of Ethiopia Birhanu Biazin Temesgen Thesis committee Thesis supervisor Prof.dr.ir. L. Stroosnijder Professor of Land Degradation and Development Wageningen University Thesis co-supervisor Dr. G. Sterk Associate professor, Department of Physical Geography Utrecht University Other members Prof. dr. P.C. de Ruiter, Wageningen University Prof. dr. H.H.G. Savenije, Delft University Prof. dr. ir. J.E. Vermaat, Free University Amsterdam Dr. ir. W.B. Hoogmoed, Wageningen University This research was conducted under the auspices of Graduate School: C.T. de Wit Production Ecology and Resource Conservation Rainwater harvesting for dryland agriculture in the Rift Valley of Ethiopia Birhanu Biazin Temesgen Thesis submitted in fulfilment of the requirements for the degree of doctor at Wageningen University by the authority of the Rector Magnificus Prof. dr. M.J. Kropff, in the presence of the Thesis Committee appointed by the Academic Board to be defended in public on Monday 16 April 2012 at 4 p.m. in the Aula. Birhanu Biazin Temesgen Rainwater harvesting for dryland agriculture in the Rift Valley of Ethiopia 162 pages. Thesis, Wageningen University, Wageningen, NL (2012) With references, with summaries in Dutch and English ISBN 978-94-6173-215-6 Financially supported by: Wageningen University (Sandwich Programme) International Foundation for Science (IFS) Sweden International Development Agency (SIDA) Acknowledgement Various individuals and institutions contributed in different forms during the three phases of proposal designing, field data collection and final writing up of my PhD thesis. I am sincerely indebted to my promoter, prof. Leo Stroosnijder for his all-round help. The field experimental set-up and rigorous measurements would have not been successfully accomplished without his constant follow-ups, technical comments and prompt reactions to on spot problems. Unlike the Dutch culture of sticking to appointments, I did not need to make any appointments to drop to his office any time I needed help. It has been a privilege for me to have him as a promoter and benefit much from his rich experiences in field experimentations and modelling. This PhD project has been initiated by my co-promoter dr. Geert Sterk. Although I knew the foregone financial constraints at the inception of my Sandwich arrangement, I decided to continue learning with Geert. His persistent and incisive scientific guidance kept me always motivated. He had shown me the way to science in a friendly relationship. My heart-felt thanks are also for dr. Melesse Temesgen who has inspired me about improved tillage techniques. We had very nice scientific discussions both in the field and offices. Dr. Abdu Abdulkedir has kept me encouraged from the inception of this PhD project. His moral and scientific support was immense. I am very grateful to the Wageningen University for the sandwich PhD fellowship. I am also indebted to Wondo Genet College of Forestry and Natural Resources and the Sweden International Development Agency (SIDA) for the financial support of my field research. The International Foundation for Science (IFS) is gratefully acknowledged for its financial support for the purchase of field equipment. I am thankful to the farmers who voluntarily made their fields available for field experimentation during 2008 through 2010 growing seasons. Especially, the family of Obbo Hirpho has made my field life tolerable and successful. The support of Sheki, Gebawo, Meisso, Hideto and Obbo Hirpho was incredible. I am happy that Gebao (my best field assistant) went back to schooling after my repeated advises and started performing well. I thank the local people for their patience when I had repeated meetings with them at various phases of the study. My enthusiasm is to see the local people adopting more apt and sustainable technologies and conserve the remnant woodlands. I am thankful to Estifanos Mathewos and Woinshet Afework for their laboratory assistances. Ashenafi Burka, Habtamu Tadesse, Geert Koster, Mathijs Kool, and Duncan Harrison contributed during the rigorous field measurements and GIS analyses. I also thank drivers Shubisa, Alemayehu, Ato Afework, Botola, Ayenachew, Milkias and Ato Wario. I would like to extend my gratitude to staff and student fellows in the Land Degradation and Development group for the valuable discussions, assistances, and friendships. Dirk Meindertsma was instrumental in facilitating the administrative and financial matters until around the middle of my PhD study. After his retirement, Marnella vd Tol and Anita Kok has replaced him impeccably. The staff and students in the group: Jan de Graaff, Saskia Keesstra, Aad Kessler, Piet Peters, Saskia Visser, Michel Riksen and Coen Ritsema and the many PhD students. Dr. Demie Moore is gratefully acknowledged for her humble and unreserved assistance for language editing of my articles. My gratitude also goes to Meaza, Asmare, Melkamu, Tefera, Abraham, Tessema, Teshale, Motuma, Vouwter, Emiru, Addisalem, Workneh, Aschu, Asefa, Firehiwot, and Betwoded for their encouragements during my stay in Wageningen. Members of the Ethiopia Orthodox Tewahido fellows at Wageningen Uiversity provided me love and spiritual strengths. My sincere thanks goes to friends and families in Ethiopia. Dr. Bekele, Dr. Fantaw, Dr. Agena, Yitayal, Mesele, Girma, Bezash, Tefera, Fikirte, Zewdiye, Biruk, Tiruye, Birkie and other members of the family for their closer follow up and special care for my wife and baby during my long absence. I would like to thank Tesfaye and Nebiat for their love and persistent friendship. My sisters, Tigist, Ketema, Tirualem, Meseret and brothers Misganaw and Abebe, I thank you for your love and encouragements. My parents sent me and all siblings to school at our early ages while many other children of our age in the neighbourhood did not get the same chance. Sending all their children to school while toiling on their farm plots has shown us their love and dedication as a parent. I dedicate my work to my parents, my wife Elisabeth and our little Yohanes. Echo, the inception of my PhD study immediately after our engagement, having our wedding in between and becoming a mother in my absence along with your busy job put you under a huge responsibility. Your enthusiastic encouragement and repeated question “how is your work going?” had different tones of constant answer from me, ‘’good’’. You taught me strength and patience. Table of Contents Chapter 1 Introduction 1 Chapter 2 Rainwater harvesting and management in rainfed agricultural systems 9 in sub-Saharan Africa – A review Chapter 3 Drought vulnerability and land-use changes in the Rift Valley drylands of Ethiopia 29 Chapter 4 The effect of long-term Maresha ploughing on soil physical properties in the 51 Central Rift Valley of Ethiopia Chapter 5 To tie or not to tie ridges for water conservation in Rift Valley 65 drylands of Ethiopia Chapter 6 Towards a participatory rainwater harvesting and management planning 87 approach in the Rift Valley dry lands of Ethiopia Chapter 7 Synthesis 111 References 123 Summary 139 Samenvatting 145 PE&RC PhD Education Certificate 149 Curriculum vitae and author’s publications 151 Chapter 1 Introduction Introduction 1.1 The challenge of agricultural production in Ethiopia The great challenge for the coming decades will be the task of increasing food production to ensure food security for the steadily growing world population, particularly for societies hosted in environmentally vulnerable areas such as sub-Saharan Africa (ICSU, 2002). In sub-Saharan Africa (SSA), human population grows by 3% a year while yields of the major food crops grow only at 1% a year implying a declining per- capita food production (Dyson, 1999; Rockström, 2003; Sachs et al., 2004). More than 41% of the population in Africa lives in drylands that cover about 43% of the continent (UNDP, 1997). In drylands, water is a key challenge for food production due to the extreme variability of rainfall, long dry seasons, and recurrent droughts and dry spells. Most hungry and poor people live in regions where water challenges pose a particular constraint to food production (Koohafkan and Stewart, 2008). Rainfall variability in Africa is twice that of temperate regions, which makes agricultural drought more frequent in Africa than anywhere else in the world (World Bank, 2004). Droughts have mainly affected the horn of Africa and the Sahel regions (IPCC, 2007; L’Hôte et al., 2002) although it occurs in all drylands of SSA. In Ethiopia, agriculture is the mainstay of the economy contributing the largest share to GDP, export trade and earnings, and employs 84% of the population (Teshome, 2006). Yet, agriculture is the most volatile sector mainly due to its dependence on rainfed systems (close to 97% of the agricultural land is rainfed) and the seasonal shocks that are frequently observed (Awulachew et al., 2005). In association with the burgeoning population, the fresh water availability per capita in the country will be less than 1000 m3 per person per year by 2050 putting it as one of the water scarce countries (Fischer and Heilig, 1997; Wallace, 2000). Apart from that, the arid, semiarid and dry sub-humid lands of Ethiopia occupy approximately 65% of the total land mass (close to 700,000 km2) of the country (EPA, 1998) and 46% of the total arable land (Yonas, 2001). Particularly, semi-arid areas cover 301,500 km2 (27 % of the country) and represent the crop production zone suffering from a serious moisture stress (Engida, 2000). The seasonal and annual rainfalls in Ethiopia are highly unpredictable and variable with more risk of crop failure in arid and semi-arid regions due to less water availability during the growing seasons (Gissila et al., 2004; Tesfaye and Walker, 2004). Production of major cereals (tef, barley, wheat, maize, sorghum and millet) showed statistically significant correlations with seasonal rainfall variability in the Amhara region of Ethiopia during 1994-2003 (Bewket, 2009).