Drought Risk Assessment using Remote Sensing and GIS: The Case of Southern Zone, Tigray Region, Ethiopia

Abstract

This study used satellite sensor data which are consistently available, cost effective and can be used to detect the onset of drought, its duration and magnitude. Moreover, an effort has been made to derive drought risk areas facing agricultural as well as meteorological drought using eight-year time series rainfall data and dekadal satellite SPOT NDVI (Normalized Difference Vegetation Index). A deviation of the current NDVI with the long-term mean NDVI, and the Vegetation Condition Index (VCI) derived from the SPOT were used in this study for drought detection and monitoring. The results revealed that large proportion of the area, i.e. 31.45% (3009km²) is at moderate drought risk level, whereas 17% (1568km²) of the area accounted for high drought risk.  It is also shown that Enderta, HintaloWajirat, Eastern part of Raya Azebo and southern part of Alamata distric that more susceptible to drought. Moreover, it has been indicated that the two remote-sensing indices used, DEV_NDVI, and VCI are complementary and were found to be sensitive indicators of drought conditions. SPOT NDVI at 1km by 1km resolution, which incorporates the long-term NDVI, is also found to be one of the best data for drought risk assessment.

Keywords: Drought, Normalized Difference Vegetation Index, Vegetation Condition Index, Risk assessment