Monitoring agricultural drought using hyper-temporal satellite observatory indicators

Ethiopia is a country frequently portrayed as drought-stricken, yet more than 80% of its population depends on rain-fed Agriculture for their livelihood. In this study, we monitored the historical pattern of agricultural drought episodes in Eastern Tigray, Northern Ethiopia, using fifteen years (2001–2015) hyper-temporal satellite datasets, to detect notorious drought episodes and map out drought-prone districts (Wereda) that require special attention. Considering the methodology, we obtained a 16-days composites Normalized Difference Vegetation Index (NDVI) time series from the United States Geological Survey (USGS) website, reprojected using dense media relative transfer (DMRT), clipped in ArcGIS software to the boundary of the Tigray region, stacked in environment for visualizing images (ENVI) software to decode quality information, filtered and masked pixels to reduce noise, removed outliers, and filled gaps caused by clouds or missing observations using the Harmonic Analysis of Time series (HANTS) algorithm. We then used the processed images to compute the annual and seasonal deviation normalized difference vegetation index (Dev-NDVI) of the study area. Findings from the annual Dev-NDVI showed that the drought events that occurred during 2005, 2006, 2009, 2010 and 2014 simultaneously affected all three Weredas. Considering seasonal Dev-NDVI, the year 2009 had the highest agricultural drought severity during the ‘Kiremt’ season (June-September). The drought spatially covered 98.6%, 93.6% and 91.5% of the total land area of Gulomekeda, Atsbi Wenberta and Kilte Awulaelo Wereda, respectively. Overall, Kilte Awulaelo experienced relatively higher drought frequency (52.55%) during the main growing seasons of the fifteen considered years, likely due to its unique biophysical characteristics. The study recommends the use of Early Warning Systems and Monitoring, the adoption of drought-resistant genotypes, water conservation measures, and community and institutional capacity building, particularly in drought-prone Wereda.