Understanding the Changing Characteristics of Droughts in Sudan and the Corresponding Components of the Hydrologic Cycle

Abstract

roughts are becoming the most expensive natural disasters in former Sudan and have exerted serious impacts on local economic development and ecological environment. The purpose of this paper is to improve understanding of the temporal and spatial variations of droughts by using the Standard Precipitation Index (SPI) and to discuss their relevance to the changes of hydrological variables in Sudan. The analysis results show that 1) droughts start in the late 1960s in Sudan and severe droughts occur during the 1980s in different regions of Sudan?the annual precipitation and soil moisture also reveal the evidence that the droughts prevail since the late 1960s; 2) the greater negative soil moistures anomalies are found in central and southern Sudan during the rainy seasons while greater negative anomalies of precipitation occur only in central Sudan compared between 1969?2009 and 1948?68; 3) the precipitation recycling ratio averaged over 1948?2009 decreases from south to north and the percentage of local actual evapotranspiration to local precipitation in dry conditions is greater than that in wet conditions; and 4) the highest (second highest) correlations appear between soil moisture and precipitation (actual evapotranspiration) and the significant decreases in annual soil moisture are associated with the decrease of annual precipitation and the increase of annual temperature. This suggests that continuous droughts in Sudan are caused jointly by the decrease of precipitation and the increase of temperature in the region.