Unified framework for model-based optimal allocation of crop areas and water

The paper presents a model-based optimization scheme for allocation of cropping areas and water. The novelty of the scheme is that rather than using highly simplified models of crop response to deficit irrigation, detailed dynamic models of crop/soil/atmosphere interactions are used to determine the crop water productivity function. While the use of such models has traditionally been considered as prohibitive in terms of computation time, the current scheme circumvents this limitation by using each model independently in a simple multi-objective optimization procedure outside of the main optimization procedure. Once the optimization problem dealing with land and water allocation has been solved, the same models are used to compute optimal irrigation schedules for each crop at each location. During the season, a simplified version of the optimization scheme can be used to update water allocation in response to discrepancies between the actual and forecasted weather or factors such as changes in water quota or crop prices. The proposed scheme is illustrated for a hypothetical farm with four fields near Davis, CA. The model AquaCrop is used to determine optimal cropping and water allocation for simultaneous cultivation of maize and sunflower at that farm.