Abegaz (Phd), AssefaChere, Zerihun2020-01-272023-11-192020-01-272023-11-192019-11http://etd.aau.edu.et/handle/12345678/20513Ranked amongst the most destructive natural disasters of the world, droughts may have severe impacts on ecosystems and society, and usually occurs from a deficiency of precipitation and water availability from normal amounts. Particularly in Ethiopia, where the economy is strongly relying on rain-fed agriculture, droughts have constantly led to widespread crop failure, food shortages and even humanitarian crises. In this favor, remote sensing data and Geographic Information System (GIS) techniques provide new opportunities for producing large information on the evolution of droughts at large spatio-temporal scales. This thesis aims to map and examine the spatio-temporal patterns of agricultural droughts and soil organic carbon stock (SOC) during 2004-2018 based on Vegetation Health Index (VHI) and Standardized Precipitation Index (SPI) at monthly time-scale in the highlands of Ethiopia. In particular, MOD11A2 Terra Land Surface Temperature and Enhanced Moderate Resolution Imaging Spectrometer Normalized Difference Vegetation Index and Climate Hazard Group Infrared Precipitation with station data (CHIRPS) monthly rainfall data were used. A simple linear regression and Pearson correlation model was applied to examine the relationship between VHI and SPI as well as to validate satellite based VHI estimation based on crop yield data. Based on the results of VHI and SPI the years 2009 and 2015 were considered as the drought years while 2006 and 2018 were taken as slight and non-drought years. The spatial analysis revealed that the central and northern highlands (Eastern, central and southern Tigray Zones, Easter Amhara Zones, East Shewa4), West and East Hararge in Oromiya and Silti and Alaba zones in Sothern Nations, Nationalities and Peoples’ region were frequently struck by agricultural drought over the last 15 years. The highest agricultural drought incidence was observed in Central Tigray (18), Eastern Tigray (17), East Shewa (16), Alaba (15), Southern Tigray (14) and Wag Himra (14). The study showed strong positive correlation between VHI and SPI. There is also strong positive correlation between VHI and detrending crop yield. In this study strong positive correlation was captured between VHI and SOC stock (R2/P = 0.41/0.000). VHI and SPI based analysis accurately indicates the onset, spatial, and temporal dynamics of agricultural drought in Ethiopia. This study can help to improve the existing agricultural drought monitoring systems carried out over Ethiopia in general and the study area in particular. Thus, decision makers can potentially use VHI and SPI in drought monitoring and early warning system. Keywords: Soil Organic Carbon, Vegetation Health Index, Standardized Precipitation Indexen-USSoil Organic Carbon, Vegetation Health Index, Standardized Precipitation IndexThesis