Spatiotemporal Dynamics Of Climate Variability Its Impact On Major Cereal Crops And Suitability Projections At Bilate Watershed Sub Basins Of Ethiopian Rift Valley
Climate variability and changes are among the hazards affecting rain-fed agriculture. The study was undertaken in Bilate Watershed, Southern Ethiopia. It aimed to evaluate the relationships between local climate and Sea Surface Temperature, realize patterns of drought, and predict future climate suitability for major cereal crops. Data were obtained from the National Meteorology Agency of Ethiopia, Statistical Agency, worldclim.org, and National Oceanic and Atmospheric Administration (NOAA). Climate data were downscaled using the Statistical Downscaling method. The climate data was analyzed using the Mann-Kendal (MK) and Modified Mann Kendal (MMK) test, Pearson correlation coefficient, and Standardized Evapotranspiration index. Maxent model was used to analyze the climatic suitability for crops. The results show that the watershed has experienced a Coefficient of Variation (CV) of 30-58% for rainfall and 0.04 to 0.14% for temperature. The MK and MMK tests revealed that significant trends were detected for summer (Z=2.9) and decreasing trends of spring rainfall (Z=-1.6). The maximum temperature trend increases for all seasons, spring Z>2.9, summer Z= 3.6, autumn Z=2.8, and winter Z= 3.23. Minimum temperatures trend were observed in spring Z= 2.7 and summer Z= 5.9. An increasing trend of minimum temperature was observed in autumn Z=3.6. With regards to rainfall and temperature relation with SST, it is positively correlated with ENSO (Nino 3.4 and IOD, except for areas in the north). In spring, IOD was positively correlated r = 0.42 with the south and northeastern parts of the watershed, while summer and winter were negatively correlated with IOD in the north. The entire watershed's rainfall is positively correlated with IOD in autumn. Positive correlations r=0.3-1 were observed with Nino3.4 regions in all seasons. It was found that in the upcoming decades, the southwestern areas of the watershed would experience a change in maximum temperature in spring by RCP8.5 scenario -1 to 1°C. The northern parts would have a change of 6.4°C in summer maximum temperature. Precipitation of the wettest month is the top-ranking contributor for Enset 81%, Annual temperature by 48.5% for maize, and precipitation of wettest month for wheat by 88.1%. The southern areas were found to be highly suitable for Enset with a suitability grade of 0.7 to 1, in both SSP4.5 and 8.5 scenarios. Analysis from Maxent indicates the watershed is less suitable for maize with a suitability grade