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Climate change impacts on food supply and water use efficiency have become an urgent issue for the agricultural researchers and governments. With climate change, water resources will be a restricting factor for agriculture, especially in arid and semi-arid areas. This paper mainly discusses the changing tendency of water balance components, maize yield and water use indices under rainfed and irrigated conditions in subareas of the Loess Plateau under the A2 and B2 scenarios with the SWAGMAN (R) Destiny model. The results show that evapotranspiration will increase in future for both rainfed and irrigated maize under both scenarios. The water use indices mentioned in this paper have the same tendency under both scenarios in the same subareas, but variability under the A2 scenario is higher than that under B2. The crop yield and water use indices will decrease for rainfed maize production in the whole Loess Plateau. With irrigation, crop yield will increase in Clay Loam-2 and Clay Loam-1 while it will decrease in Light Loam and Sandy Loam under the A2 scenario and B2 scenarios in 2020, 2050 and 2080 respectively. The evapotranspiration efficiency and ratio of evapotranspiration and irrigation under irrigated maize will increase in Clay Loam-2, Clay Loam-1, Light Loam and Sandy Loam under both scenarios. Crop water use efficiency, irrigation water use efficiency and total water use efficiency will decrease under the A2 and B2 scenarios during irrigated maize growth. Therefore, for the rainfed crop, it is necessary to improve water harvesting technology so as to meet the increasing crop water requirements with climate change; while, for the irrigated crop, it is vital to enhance soil water capacity in order to make good use of the irrigated water. Copyright (C) 2013 John Wiley & Sons, Ltd.