Owing to contradicted scientific results, trends in drought due to global warming have been assigned with medium confidence. Drought will likely continue inputting immense pressure on food security in fragile ecosystems like Sub-saharan Africa (SSA). As an adaptation measure to severe drought events since the 1980s, the overall goal of irrigated schemes (foreign exchange earnings) thus has been shifted to sustain food security. This study assessed the impacts of such drought-driven agricultural policy and future climate change on the performance of large irrigated schemes in SSA, with special emphasis on the Gezira scheme, GS (0.88 mha), Sudan. The optimized scenario of the baseline period, developed in GAMS (the general algebraic modeling system), showed that the expansion of food crops on the expensive of cash crops resulted in a reduction of 83 % in gross net benefits and loss of 63 % in irrigation water in the GS since the severe drought of 1984. The biased corrected rainfall and temperature outputs of three randomly selected regional climate models (RCMs) under unmitigated pathways (RCP 8.5), suggested increased rainfall of 40 mm, increased temperature of 3.3 degrees C and 5 % increase in reference evapotranspiration for the period 2040-2070, compared to the baseline (1960-1990). The predicted conditions experienced neither extreme drought nor extreme wet events; however, severe and moderately drought events remain a challenge up to 2060. Due to climate change and current water management practices, the FAO-Aquacrop predicted reductions in crop yields and water productivity, especially for cotton and sorghum of 40 and 29 % respectively. Optimized future crop scenarios indicate that food crops such as sorghum and wheat are not viable. Cash (cotton) and soil fertility maintenance crops (groundnuts) would be better for sustaining economic viability. The agricultural policy and water management practices thus should be revisited to keep pace with future climate changes.
