AquaVar decision support system for water resource management: Lessons learned from the first five years of operation

Abstract Decision support systems (DSS) based on physically based numerical models are standard tools used by water services and utilities. However, few DSS based on holistic approaches combining distributed hydrological, hydraulic, and hydrogeological models are operationally exploited. This holistic approach was adopted for the development of the AquaVar DSS, used for water resource management in the French Mediterranean Var watershed. The year 2019 marked the initial use of the DSS in its operational environment. Over the next 5 years, multiple hydrological events allowed to test the performance of the DSS. The results show that the tool is capable of simulating peak flows associated with two extreme rainfall events (storms Alex and Aline). For a moderate flood, the real‐time functionality was able to simulate forecast discharges 26 h before the flood peak, with a maximum local error of 30%. Finally, simulations for the drought period 2022–2023 highlighted the essential need for DSS to evolve in line with changing climatic conditions, which give rise to unprecedented hydrological processes. The lessons learned from these first 5 years of AquaVar use under operational conditions are synthesized, addressing various topics such as DSS modularity, evolution, data positioning, technology, and governance.