MODELING IMPACTS OF CLIMATE CHANGE AND VARIABILITY ON WHEAT (TRITICUM AESTIVUM L.) PRODUCTION IN SINANA DISTRICT, SOUTHEASTERN ETHIOPIA

he national economy of Ethiopia is dependent on agricultural sector which is heavily dependent on rainfed system. The impacts of climate change and variability are very local in nature, hence a local level and crop specific understanding of the impact is extremely important. Wheat is one of the food security crops in Ethiopia which is critically sensitive to the impacts of climate change and variability. With this understanding, a study was conducted at two stations in Sinana district to model impacts of climate change and variability on wheat production under past and future climate scenarios. Historical climate data (1984-2016) and future climate data (2040-2090) downscaled using the spatially explicit daily weather generator that uses third order Markov chain climate simulator for ensemble of all General Circulation Models, were analyzed to understand the local level climate change and variability. Past and future climates were analyzed in terms of changes in annual, seasonal and monthly rainfall statistics. Dry spell length and climate extreme indices were analyzed using INSTAT v3.37 and RClimDex v3.3.3 software analytical tools respectively. The result of historical data analysis suggested that, annual and kiremt rainfall total was increased by 9.1 mm/yr and 6.1 mm/yr at Sinana 2.8 mm/yr and 2.9 mm/yr at Robe station respectively. The mean minimum temperatures at Sinana and mean maximum and minimum temperatures at Robe showed a significant increase. Correlation of wheat yield with rainfall was done and the result showed kiremt rain had an impact on Madda walabu yield with r =-0.292 and r=0.018 at Sinana and Robe respectively. For Sofumer, the seasonal rainfall of kiremt with r =0.181 and r=0.453 at Sinana and Robe showed positive a non-significant positive correlation respectively. Observed agronomic and soil data were used to calibrate and validate the Crop model of Decision Support for Agro-technology Transfer model. The model was then used to simulate the impact of future climate changes and variability in bread wheat yield of Madda walabu and Sofumer varieties at Sinana district. The results revealed that climate change and variability caused variability on wheat productivity in Sinana district within both time slices. There is a positive impact on Madda walabu variety in both time period at Sinana while negative impact was simulated at Robe except in 2080’s under RCP4.5 and in 2050’s and 2080’s under RCP8.5 scenarios. Madda walabu yield was simulated to increase by up to 74.7 % in 2050’s under RCP8.5 scenario at Sinana and decreased up to -21.4% at Robe in 2050’s under RCP4.5 scenario relative to the baseline due to climate change impacts. Sofumer yield was increased by 7.3 % and 20.6 % in 2050’s and 2080’s under RCP4.5 scenario relative to baseline and it was increased up to 15.7 % for RCP8.5 scenario at Sinana. Therefore; climate change and variability had a severe impact that justifies need for site specific study. Therefore, future agricultural practices should benefit from agro weather advisory service for farming decision in study areas.