CLIMATE CHANGE IMPACT ASSESSMENT ON CROP WATER REQUIREMENT OF SORGHUM ON BORKENA RIVER CATCHMENT, AWASH SUB-BASIN

Abstract

Assessment of climate variability at local level has enormous advantage in Ethiopia, where the driver of the economy is agriculture. This study was conducted to analyze rainfall and temperature trend and variability to guide sorghum production in Borkena catchment. The region is known by its food insecurity problem due to increasing population and increasing natural resource degradation as well as unpredictability of rainfall. Marksim software was used to download future climatic parameter. The onset, end of the growing season and the Length of Growing Period were analyzed using Instat software version 3.37. Temporal variability and extreme values of selected rainfall and temperature indices were analysed and trends were evaluated using Sen’s slope estimator and Mann–Kendall trend test methods. crop water requirement was calculated by using CROPWATE model window 8.0. The mean annual maximum and minimum temperature exhibited a significant warming trend of from 0.1 –1.6 °C and 0.1–0.4 °C per decade respectively. Depending on the emission scenarios, maximum and minimum temperature by the 2050 would increase by 1.5 – 2.1 and 0.5 – 1.3 °C, respectively. The mean annual rainfall varied from slightly over 918.1 mm in Kabie to more than 1192.9 mm in Haik stations with CV 12.3 % and 16% respectively. Kiremt rainfall varied from 681.9 mm in Kombolch to 748.1 mm in Haik with CV 17.9% and 23.8% respectively. Belg season rain varied from 187.9 mm in Kabie to 328.4 mm in Haik with CV 44.5% and 37.9% respectively. The mean onset, Cessation and LGS of the main growing season was found to be at Days of year (DOY) 146, 284 and 138 days at kombolcha; DOY 150, 286 and 136 days at Haik; and DOY 150, 287 and 136 days at Majete and DOY 166, 275 and 109 days for Kabie respectively. Projections from marksim GCMs suggest that future annual rainfall will change by - 10.3 to 38.2 % in 2030 and -12.1 to 29.6 % in 2050 respectively. The Eto was low in January (2.93 mm day-1) due to less radiation intensity and high during Feb to Oct xix (3.33 and 3.42 mm day-1), reaching maximum value at May (3.89 mm day-1) and declined during November and December (3.17 to 2.91 mm day-1). CROPWAT Result shows that the crop evapotranspiration (ETc) of Sorghum crop was high during development mid-season and late stages (23.4, 105.3, 186 and 163) mm/stage respectively. when compared to base period, the crop evapotranspiration in both future periods (2030 and 2050) shows an increment by 41.7%, and 42.9% in 2030 and 43.2%, and 46.7% in 2050 for Rcp 4.5 and Rcp 8.5 scenarios respectively. To suggest that developing countries like Ethiopia, in particular are more susceptible to the significant influences of climate variability. This is because of their low adaptive capacity and high sensitivity of their socio-economic systems to climate variability and change. Therefore, the concerned bodies should take in to consideration the precipitation and temperature variability of the area in to their climate change adaptation strategies.