Drought risk during the early growing season in Sahelian Sudan

The African countries are known to be the most vulnerable to climate change and variability and food insecurity. An effort is devoted in this study to assess the year-by-year drought risk to sorghum and millet during the onset of the growing season in the Sudanese Sahel. A recently developed drought risk index (DRI) is used for this purpose. The DRI is a multiplicative formula of six variables, namely frequency, duration, severity and spatial extent of drought, production level and coping capacity through irrigation. A significant finding is that drought at the early stage of the growing season can pose a dramatic risk to crop yield. Analysis and results for 12 provincial states of the region reveal a strong relationship between the probabilistic DRI and yield of these major crops. This relationship offers vital information of a considerable potential risk to crop yield if the drought occurs as early as June and July. Significant proportion of the variations in the crop yield can be explained by the DRI. June DRI expresses up to 68 and 90 % of the variations in sorghum and millet yields, respectively. Up to 84 and 68 % of the respective yields can be explained by June-July DRI. Based on the regional analysis, the median area under drought risk for the entire data period (1970-2006) is 43 % for sorghum and 40 % for millet. From the frequency analysis, the occurrence probabilities of these medians are 41 and 34 %, respectively. Evidence is presented that the agricultural drought risk in this part of the African Sahel is still high during the period 1991 onwards when annual rainfall is said to have been recovering. The present results provide useful information for drought forecasters and decision making in crop and disaster planning and management, especially in view of projected drier and warmer climate conditions during this part of the growing season. Also, the DRI proves to be robust spatially and temporally for agricultural monitoring under situations of limited meteorological data and could be tested for other regions in the African Sahel.