Abstract: 【Objective】 Water use efficiency (WUE) is an important index of agricultural water management and decision. Water shortage is serious and winter wheat is the main water consuming plant, so this study analysed the winter wheat WUE to provide information and support for decision makers for winter wheat water saving irrigation and yield balance in Beijing.【Method】 The response characteristics of yield and WUE of winter wheat under different rainfall year types and irrigation treatments were analyzed using the experimental data collected in 2011-2012, 2012-2013 and 2013-2014 to simulate and validate the model under different years and irrigations and then calibrate the AquaCrop model in National Precision Agriculture Research and Demonstration base. The daily precipitations of winter wheat growing period were collected from 2004 to 2014 in Beijing, and then using the Pearson-III distribution to divide three precipitation types, wet year (2012-2013), normal year (2009-2010) and dry year (2005-2006). The response characteristics of grain yield and WUE were simulated under three precipitation types and 14 irrigation scenarios using the AquaCrop model. 【Result】 The correlation coefficient (R²), root mean square error (RMSE) and consistency (d ) of simulated and measured values of yield were 0.99, 0.3 t·hm^-2 and 0.99, respectively. The simulated and measured values of winter wheat grain WUE were 1.72 kg·m^-3 in 2011-2012 growth period, 1.67 kg·m^-3 in 2012-2013 growth period and 1.27, 1.74 and 1.64 kg·m^-3 under rainfall, normal irrigation and over-irrigation in 2013-2014. The highest WUE was under normal irrigation, the second was under over-irrigation and the lowest was under rainfall. The response characters of winter wheat grain yield and WUE under three precipitation types were simulated by AquaCrop model. The irrigations were 35 and 50 mm when yield and WUE were the highest in wet year, 35 and 40 mm in normal year and 65 mm in dry year, respectively.【Conclusion】 The results of the study show that the AquaCrop model well predicted the winter wheat grain yield and WUE under different years and irrigations in Beijing. The grain yield and WUE increased when irrigations increased, began to decrease when reached the maximum values. The plants could improve the WUE through their adaptation when water is in shortage, the WUE decreased with rainfall or irrigation increasing, therefore the ranking of the WUE was dry year, normal year and wet year under three precipitation types. Therefore both the yield and WUE must be considered in development of the irrigation strategies for winter wheat. The AquaCrop model can be used to provide guidance for the field irrigation and decision making of winter wheat in Beijing region. In this study, the grain yield and WUE were only simulated under wet year, normal year and dry year in over-wintering period, regreen period, stem elongation period, blooming period and grain filing period, the effects of different irrigations on grain yield and WUE were not considered in different periods, which need to be further studied and verified.

Key words: winter wheat, AquaCrop model, water use efficiency, biomass, grain yield