IMPACTS OF CLIMATE CHANGE ON RAINFED MAIZE PRODUCTION IN RIFT VALLEY LAKES BASINS OF ETHIOPIA; HAWASSA AS CASE STUDY

Abstract

Agriculture is mainstay of Ethiopian economy. Developing country like Ethiopia suffers from effects of climate change, due to their limited economic capability to build irrigation projects to reduce climate change impact on crop production. This study evaluates climate change impact on rainfed maize production in rift valley lakes basins of Ethiopia. First, outputs of 15 General Circulation Models (GCMs) under two emission scenarios (SRA1B and SRB1) are statistically downscaled by using LARS-WG software. Probability assessment of bounded range with known distributions is used to deal with the uncertainties of GCMs’ outputs. These GCMs outputs are weighted by considering the ability of each model to simulate historical records. The study result indicates that LARS-WG 5.5 model is more uncertain to simulate future mean rainfall than generating maximum and minimum mean temperatures hereby GCMs weight difference for rainfall mean is 0.83 whereas weight difference for minimum and maximum mean temperatures is 0.09. AquaCrop, version 4 developed by FAO that simulates the crop yield response to water deficit conditions, is employed to assess potential rainfed maize production in the study area with and without climate change. The study results indicate minimum and maximum temperatures absolute increase in the range of 0.34 0 C to 0.580 C, 0.940 C to 1.80 C and 1.420 C to 3.20 C and 0.320 C to 0.560 C, 0.910 C to 1.80 C and 1.340 C to 3.0350 C respectively in the near-term (2020s), mid-term (2055s) and long-term (2090s) under both emission scenarios. The expected percentage change of rainfall during these three time periods considering this GCMs weight difference into account ranges from -2.3 to 7%, 0.375 to 15.83% and 2.625 to 31.1%. Maize yields are expected to increase with the range of 3.63% to 7%, 5.39% to 14.08%, and 6.83% to 15.61%, during the same time periods. Unlike many studies in the world this study result show that maize yield increased in coming three time periods under both emission scenarios. Due to rainfall increase with temperature increase maize yield is expected to increase in future for this study area by using only rainfall. In conclusion, the results indicate that climate change will respond positively to climate change impact on maize yield production for this district if all field management, soil fertility and crop variety improved; but since there is rainfall variability among the seasons planting date should be scheduled well to combat water stress on crops