The document discusses an event-driven architecture for decision support related to water quality monitoring. It describes a use case of monitoring for cyanobacterial blooms in a reservoir in France. The architecture includes sensors to collect pH values, an event processing layer to analyze the data as it arrives, and a decision maker module to notify authorities if pH variation exceeds 0.5 in 24 hours, indicating a bloom. The proposed architecture aims to process measurements quickly as they arrive to support timely decision making.