Traits related with water productivity in dryland cropping interact in multiple ways to influence final grain yield. The APSIM-Wheat model has proved useful to address how to best combine traits for region-specific and management-specific adaptation of new genotypes. However, the model requires further effort to accurately simulate important traits associated with enhanced water productivity, especially during the vegetative stage. Field experiments were conducted in 2015 and 2016 to assess variation and covariation in traits related to canopy development, e.g. tillering and leaf area development. An improved wheat model has been developed with, in particular, distinction of between the different tillers and their characteristics (e.g. leaf size and life span) by using the plant model framework (PMF) in APSIM Next Generation. The new model allows more accurate predictions of major traits related to canopy development (e.g. tiller number and leaf area index) during the growing season. The improved wheat model was evaluated in different environments and can be used to evaluate genotypic variations in traits related to water productivity.