When reviewing a groundwater concentration trend chart, unexplained spikes or drops become much clearer when annotated with real-world events. A ChartAnnotation linked to a siteId and placed at an annotationDate provides that context — for example, a label reading "Pump-and-treat startup" or "Storm event" explains why concentrations changed at that point in the timeline. The category field helps group annotations by type — regulatory, operational, sampling anomaly — and the color field allows visual distinction between different categories on the chart. Annotations are authored centrally and appear on all charts for the site, making them a lightweight but powerful tool for compliance storytelling in regulatory reports.
Technical section
Data model, API, and internals — visible to developers.