This paper analyses the impacts and water policy implications of an increase of perennial crops on irrigation water requirements and on the vulnerability of the agricultural system to climatic events in the case of the Guadalquivir River basin. As indicated by the EU Water Framework Directive (WFD), the characterisation of a river basin requires information on the major economic drivers and pressures at river basin scale. Guadalquivir River basin (southern Spain) can be considered a representative Mediterranean case study that has faced basin closure and continues the trend towards increased crop intensification and greater water-use efficiency. Our result shows an increased vulnerability to drought and water scarcity in the basin due to the expansion of irrigated perennial crops and a decrease of RIS (relative irrigation supply) from 0.70 to 0.56 in the period 2000–2021, thereby forcing farmers to adopt deficit irrigation techniques. The potential increase in the frequency of droughts and the growth of irrigation water requirements (IWR) due to higher temperatures, raise the vulnerability of the system to extreme climate events. Such findings can be employed to support the efficient allocation of water resources in order to improve water policy through its adaptation to increasing risks related to droughts and water scarcity. •The evolution of irrigated area in Guadalquivir River basin is characterised by an increasing share of perennial crops.•IWR have increased continuously due to changes in crop patterns (intensification).•Since IWR exceed availability, the irrigation system applies deficit irrigation as a response, with a decreasing RIS.