The study was conducted in the Bilate River Watershed. Bilate River is one of the inland rivers of Ethiopia that drains in to the northern watershed of the Lake Abaya-Chamo Drainage Basin which forms part of the Main Ethiopian Rift and in turn is part of an active rift system of the Great Rift Valley in Africa. This study examined the extent and nature of rainfall variability from recorded data while estimation of evapotranspiration was derived from recorded weather data. Future climate scenarios of precipitation and temperature for the Bilate Watershed were also generated. Analysis of rainfall variability was made by the rainfall anomaly index, coefficient of variance and Precipitation Concentration Index. The FAO-56 reference ET (ETo) approach was used to determine the amount of evapotranspiration. Estimation of the onset and the end of the growing season, and the length of the growing period was done using Instat software. The results show that mean annual rainfall of the upper (2307 m.a.s.l), middle (1772 m.a.s.l) and lower (1361 m.a.s.l) altitude zones of the watershed are in the order of 1100 mm, 1070 mm and 785 mm with CV of 12%, 15% and 17% respectively. Based on the rainfall data record of the latest 30 years, there was a high temporal anomaly in rainfall between 1980 and 2013. The wettest years recorded a Rainfall Anomaly Index of +5, +6 and +8 for stations in the upper, middle and lower altitude zones respectively, where the driest year recorded value is -5 in all the stations. The average onset date of rainfall for the upper zone is April 3+ 8 days, for the middle zone April 10 + 10 days and for the lower zone April 11+ 11 days with CV of 23%, 26% and 29% respectively. The average end dates of the rainy season in the upper and middle zones are October 3+ 5 days and September 25+ 7 days with CV 5% and 7%. The main rainy season ends earlier in the lower zone; it is on July 12 + 10 days with CV of 14%. Climate change scenarios were generated for two Representative Concentration Pathways (RCPs): RCP 4.5 and RCP 8.5 using 20 GCMs from CMIP5 bias-corrected under three future time slices, near-term (2010-2039), mid-century (2040-2069) and end-century (2071-2099). Rainfall is projected to increase in total amount under all-time slices and emissions pathways but with pronounced inter and intra-variability. Minimum temperature will significantly increase during mid-century by 1.810C (RCP 4.5) and xiii 2.550C (RCP 8.5) and by 2.10C (RCP 4.5) and 4.270C (RCP8.5) during end-century. The projected increase in maximum temperature during mid-century is 1.430C under RCP 4.5 and 1.99 0C under RCP 8.5 and during end-century by 1.650C under RCP 4.5 and 3.50C under RCP8.5 during end-century. The Soil and Water Assessment Tool (SWAT) model was selected to simulate stream flow of the watershed. The Alaba Kulito gauging station monthly stream flows from 1990 to 1996 and 1997 to 2002 were used for stream flow calibration and validation respectively. The respective statistical results of the coefficient of determination (R2), Nash–Sutcliffe coefficient (NSE) and percent bias (PB) are 0.79, 0.78 and 0.56 for the calibration period and 0.64, 0.60 and -21.7 for the validation period which show that the model predicted the stream flow at the Alaba Kulito gauging station reasonably. The annual stream flow increased progressively throughout the century for all time periods under both RCP scenarios. The increases under RCP 8.5 scenario are the larger compared to RCP 4.5 scenarios, approximately 42.42% during the 2080s period. The six GCMs selected to see the uncertainties related to GCMs suggest that the river flow will change by small amounts of −6.18 to 7.83% change compared with the baseline. The simulated runoff in the Bilate River depends on the projected amount of rainfall embedded in the GCM structures selected to simulate the future climate and is less dependent on the local temperature increment. The study also assessed the farmers‘ perceptions of the changes on climatic variables and their adaptation options to the impacts of climate variability and change. The determinant factors that influence the choice of farmers to climate change adaptation were also investigated. Above 92% of the surveyed farm households perceived variability and change in climatic variables but 59% of the households participated in one or other of the six major adaptation strategies which most prevailed inside farmers of the watershed. Changing crop variety, using water harvesting scheme, intensifying irrigation, using cover crop or/and mulching, reducing the number of livestock owned and getting offfarm jobs are the main adaptation strategies used by the farming households. The results from the binary logistic model further showed that age and educational level of the household head, farm size and the income level of the household are household characteristics that significantly affect the choice of adaptation options, while access to climate information in the form of seasonal forecasts and local agro ecology are other factors that determined the selection of adaptation methods by the farming households in the study area. The main constraints to adaptation to climate change in the study area were seen to be the knowledge gap in the form of lack of information, shortage of labour and minimal land size. These were the three most explained constraints to climate change as explained by responding household heads. / Environmental Sciences / D. Litt. et Phil. (Environmental Sciences)

In the dominantly small-scale subsistence agricultural system of Ethiopia, where most of the organic inputs are not returned to soil and land is not used based on its best suitability, the contribution of agriculture to climate change mitigation/adaptation through reduction of greenhouse gases emission is undermined. When this low-input agricultural practice is coupled with rugged topography, high population pressure, generally low soil fertility, and looming climate change, ensuring food and nutrition security of society as well as sustainable use of land resources is practically impossible. Under such circumstances, finding alternative land uses, through scientific investigation, that meet the triple mandates of climate-smart agriculture under current and future climate is imperative. In view of this, a study was conducted in Hades Sub-watershed, eastern Ethiopia, to evaluate the carbon stock of major land uses, evaluate suitability of land for rainfed production of sorghum (Sorghum bicolor L.), Maize (Zea mays L.), coffee (Coffea arabica), upland rice (Oryza sativa L.) and finger millet (Eleusine coracana L.), and project biomass production of late-maturing sorghum and maize varieties under changing climate and its contribution to carbon sequestration and reduction of greenhouse gases (GHGs) emission. Soil and vegetation samples were collected following recommended procedures. Secondary data on required crop parameters were collected for model calibration and validation in the biomass projection study made using the AquaCrop v6.0 model. Climate data of the study area was obtained from the National Meteorology Agency of Ethiopia and analyzed following standard procedures. Near-century (NC) (2017-2039) and Mid-century (MC) (2040-2069) climate was projected under two emission scenarios (RCP4.5 and RCP8.5) using four models (CNRM-CERFACS-CNRM-CM5, ICHEC-EC-Earth, MOHC-HadGEM2-ES, and MPI-M-MPI-ESM-LR) and a Multi-model Ensemble. Biomass production projection, for the climate projected under the two emission scenarios using the four models and the ensemble, was made for late-maturing sorghum (Muyira-1) and maize (BH661) varieties. From the projected biomass, organic carbon and its equivalent CO2 were estimated. Furthermore, adaptation measures, involving adjusting planting dates and irrigation, under the changing climate were evaluated for their influence on biomass production under the time slices, RCPs, and models mentioned above. The carbon stock assessment study was conducted on four major land uses (cultivated, grazing, coffee agroforestry, and forest lands) identified in the study area. The land suitability assessment, using the maximum limitation method, study was conducted on four soil mapping units identified in the sub-watershed. Results indicate that total organic carbon stock (soil, litter plus live vegetation) in the sub-watershed ranged from 138.95 ton ha-1 in the crop land to 496.26 ton ha-1 in the natural forest. The soil organic carbon stock was found to be relatively higher than that of the vegetation carbon stock in the natural forest and coffee agroforestry land uses. The results of suitability evaluation revealed that the maximum current and potential (after corrective xix measures are taken) land suitability class for production of late-maturing sorghum (180-240 days cycle), maize (180-210 days crop cycle), finger millet (120 – 150 days cycle) and coffee in the sub-watershed is marginally suitable (S3c). The maximum current and potential land suitability for upland rice (120 days) is not suitable (N2c). The major permanent limiting factor is low mean temperature (14.6 C) of the growing period in the study area as compared to the optimum temperature required for optimum growth of the selected crops. The major soil and landscape limitations include steep slope, poor drainage of low-lying areas, shallow effective root zone in the upper slopes, low organic matter and available P for sorghum and maize, high pH for maize and wetness for coffee. In all the climate models and emission scenarios, minimum and maximum temperature increment is high during June-July-August-September (JJAS) compared with the other seasons. The modest rise in minimum temperature and the slight increment of maximum temperature during the crop growing seasons (February-March-April-May (FMAM) and JJAS will benefit late-maturing sorghum and maize production in the study area. For the same model, the projected biomass yield and organic carbon sequestration of the two crop varieties varied with time slice and the type of emission scenario used. Generally, increasing biomass production and carbon sequestration were projected for Mid-century (MC) than Near-century (NC) for most of the models used. Late planting would increase sorghum biomass yield and the corresponding organic carbon as compared to early planting as projected by most of the models under both RCPs. Most models predicted an increase in maize biomass yield and organic carbon sequestration if supplementary irrigation is used. The results of this study indicate that the current land uses are not enhancing carbon sequestration because of their exploitative nature and the soil/landscape and climate are not optimum for production of the crops studied. The rise in temperature in the coming 50 years is expected to create a more favorable condition for production of late-maturing sorghum and maize varieties. In order to enhance carbon sequestration, soil productivity and crop yield, and reduce greenhouse gas emissions, the current land uses and their management require re-visiting. / College of Agriculture and Environmental Sciences / Ph. D. (Environmental Sciences)

Land degradation has been a global agenda. It has been affecting both developed and developing nations (including Ethiopia). The overall objective of the study was to assess the impact of landscape restoration (including area closure) on the environment and farmers‘ livelihood in Hita-Borkena watershed, northeastern Ethiopia. Three Landsat images (1986, 2001 and 2015) were used to detect land cover dynamics. Laboratory analysis of selected soil physico-chemical properties were made to compare the soil properties of closed/restored and open grazing areas. Household questionnaire was administered to investigate environmental problems before and after landscape restoration, the role of area closure and different conservation measures, and the impact of the restoration on farmers‘ livelihood. A total of 255 household heads were selected randomly for the questionnaire survey. This survey was also substantiated by interviewing agricultural experts, observation and reviewing reports prepared by Kalu District Agriculture Office. Both descriptive and inferential statistics were employed to analyze quantitative data. Besides, qualitative approach was implemented in order to analyze qualitative data. The study found out that forestlands and shrublands shrunk through 1986 – 2015, grasslands expanded mainly due to the implementation of area closure under MERET project since 2001. The study revealed that better organic matter, total nitrogen, clay and silt contents, CEC and total porosity were recorded under area closure than under open grazing land. However, both available P and K were found minimum under the former land use type. This may be due to the reason that such nutrients exist more in unavailable form or it may be because of the fact that large amount of those nutrients are extracted by the restored vegetation. The study showed that rates of soil erosion, overgrazing and illegal cutting of trees were relatively higher before landscape restoration. The respondents also appreciated the positive role of land restoration in improving the fertility of the soils of the study watershed and then the positive impact to their livelihood. Based on the results of the study, it is recommended that similar restoration activities shall be implemented in similar environments in Ethiopia to improve both the environment and farmers‘ livelihood / Geography / Ph. D. (Geography)