Analyzing Drought Conditions, Interventions and Mapping of Vulnerable Areas using NDVI and SPI Indices in Eastern Ethiopia, Somali Region

Abstract

Analysis of a long-term temporal and spatial drought conditions in Somali region was done using Standardized Precipitation Index (SPI) and Coefficient of Variation (CV) for 6 meteorological stations and Normalized Difference Vegetation Index (NDVI) analysis were performed by enhancing images from Landsat 5 TM of two different years. CV was computed for Belg season, Deyr season and yearly basis. Rainfall variability for Belg and Deyr was higher than annual variability. Characterization of the temporal variation of drought using 3-months and 6-months SPI for each meteorological station were analyzed and plotted against long time series in yearly basis. The NDVI values and SPI indices were able to show extent and variability of drought. The 3-months SPI results revealed that maximum frequency of severe drought events were experienced in Gode (7 times), followed by Hurso (6 times) within the study period. The 6-months SPI results show that less frequency of dry and wet events were observed in the entire study period as compared to 3-months SPI results. The frequency of any drought events (moderate to extreme) occurrence in the study area is once in every two years at all stations. Whereas, severe and extreme drought event in majority of study area is commenced nearly once in three years with the exception of Degahabur having once in five years. Overall, a preliminary comparison between results obtained using the SPI and NDVI shows a general good agreements.