© 2021 The Authors Water Practice & Technology Vol 16 No 3 864 doi: 10.2166/wpt.2021.033 Modeling climate change impacts on crop water demand, middle Awash River basin, case study of Berehet woreda Negash Tessema Robaa,*, Asfaw Kebede Kassab and Dame Yadeta Geletac a Water Resources and Irrigation Engineering Department, Haramaya Institute of Technology, Haramaya University, P.O. Box 138, Dire Dawa, Ethiopia b Hydraulic and Water Resources Engineering Department, Haramaya Institute of Technology, Haramaya University, P.O. Box 138, Dire Dawa, Ethiopia c Natural Resources Management Department, College of Dry Land Agriculture, Samara University, P.O. Box 132, Samara, Ethiopia *Corresponding author. E-mail:
[email protected] Abstract Climate change mainly affects crops via impacting evapotranspiration. This study quantifies climate change impacts on evapotranspiration, crop water requirement, and irrigation water demand. Seventeen GCMs from the MarkSim-GCM were used for RCP 4.5 and 8.5 scenarios for future projection. A soil sample was collected from 15 points from the maize production area. Based on USDA soil textural classification, the soil is classified as silt loam (higher class), clay loam (middle class), and clay loam (lower class). The crop growing season onset and offset were determined using the Markov chain model and compared with the farmer’s indigenous experience. The main rainy season (Kiremt) starts during the 1st meteorological decade of June for baseline period and 2nd decade to 3rd decade of June for both RCP 4.5 and RCP 8.5 of near (2020s) and mid (2050s) future period. The offset date is in the range of 270 (base period), RCP 4.5 (278, 284), and RCP 8.5 (281, 274) DOY for baseline, near, and mid future.