Winter wheat yields were simlulated by a model requiring climatic data as input for estimating crop evapotranspiration and phenological development. An assumed relationship between the winter wheat yields and the amount and timing of crop water use was optimized to simulate yields for two case studies: a single season, irrigated wheat study, and a multi-year, dryland wheat study. The model explained more than 90% of the variance of wheat yields in the irrigated study where total irrigation amounts varied between 0 and 55 cm. About 40% of the variance was explained for annual yields from a 21-year, dryland winter wheat study
