Modelling the effect of field management on crop water productivity and catchment hydrology

By linking a crop water productivity model (AquaCrop) to a lumped conceptual hydrological model (VHM), we aimed to develop a general modeling procedure to evaluate the impact of field management on WPET and catchment hydrology. To avoid disadvantages related to other model approaches, we specifically aimed at a procedure that (i) can be applied for both current and future climatic conditions, (ii) is widely applicable and generally relevant, i.e. also for developing countries, and (iii) requires a relatively small number of explicit parameters and mostly-intuitive input variables. The linkage between AquaCrop and VHM is tested for two catchments in Flanders with a high proportion of agricultural land. After the VHM model is calibrated and AquaCrop simulations are run for the different land units (crop-soil combinations) of the catchment, the response behaviour of the VHM unsaturated zone model and the AquaCrop soil water balance is compared. Differences are identified and interpreted and a final coupling of the two models is established trough the water balance of the unsaturated zone. Thereby the overland runoff and water percolation to the groundwater or subsurface flow are the most crucial linkage components. After both models are linked different field management scenarios can be investigated with respect to their effect on both WPET and catchment hydrology.