An irrigation module was developed to determine irrigation water requirements within the SPHY model. The irrigation module is based on the Plant Water Stress curve and uses only one parameter (Management Allowable Depletion). For each crop the user can indicate between which dates irrigation is applied. The new irrigation module was tested in the Campo de Cartagena catchment (SE Spain), which is characterized by intensive irrigated agriculture. In a climate change impact assessment we showed how irrigation water requirements change in the future and how the changes in irrigation demand affect the land use distribution in the study area.