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Climate change impacts on food production and water use efficiency are becoming more and more important. This paper mainly discusses the climate change effects on water use indices and maize yield under rainfed and irrigated conditions projected by three climate models in the Murray Darling Basin, Australia in 2020, 2050 and 2080 under A2 and B2 scenarios. The climate prediction results show that it is similar to the future precipitation and temperature projected by three climate models for the same time slices. For rainfed and irrigated maize, the crop yield, the potential and actual evapotranspiration will increase by 3-32, 3-12, 30-45 and 32-45, 3-15, 6-15% under both scenarios in the future during the maize growth period compared with the baseline respectively. Water use indices of maize under rainfed conditions will decrease and the variable increment will gradually be larger in the future, including evapotranspiration efficiency, crop water use efficiency and total water use efficiency. However, all the water use indices analysed under irrigated conditions will increase. The variation for evapotranspiration efficiency, ratio of evapotranspiration and irrigation is around 20%, but the variation for the other three indices is more than 30%. The projection results also indicate that the indices under the B2 scenario are smaller than those under A2 although the variable tendency and range are consistent. The conclusions suggest that it is significant to develop irrigated agriculture so as to mitigate climate change effects on crop production in the Murray Darling Basin. Copyright (c) 2015 John Wiley & Sons, Ltd.