Comparison of the spatial and temporal variability of drought indices in Somalia and Lake Chad Basin

Abstract

The science and dynamics underlying drought is complex, yet understandable if approached carefully using scientific method. In this paper, scientific perspective was applied to explain and compare drought indices in Somalia and Lake Chad Basin (LCB). Geographic information system (GIS) was used to analyze similarities and differences of locational attributes of temporal and spatial drought data in both regions. There was a similarity in the thirty-year annual precipitation, aridity index and spatial distribution of surface water bodies. Net primary production (NPP) was around -10 g carbon per square meter per year (gcm^-2yr^-1) in south of Somalia and -20 gcm^-2yr^-1 in the north in 2007. In 2009, the NPP dropped sharply to near -80 gcm^-2yr^-1everywhere in the Somalia. In contrast, NPP has been increasing gradually in LCB from -10 gcm^-2yr^-1 in 2007 to near 100 gcm^-2yr^-1 in 2010. Standard precipitation index (SPI) analysis indicates increase in SPI value from 0 (near normal) in 2009 to around 1.3 (moderately wet) in 2010 in LCB. In Somalia however, there was a corresponding decrease from 0 to -2 (extremely dry). Continued decrease in precipitation southwards in Somalia appears to have triggered the present drought. The threat of drought in LCB has not been given adequate coverage partly because the Sahel region today may have been receiving just enough precipitation. The lessons from the current drought in Horn of Africa are however, a reminder of the potential threat facing over 30 million inhabitants of LCB.

Keywords: Somalia, Lake Chad Basin, drought, standard precipitation index, aridity, water resources.