An unusual and useful property of PostgreSQL databases is that they allow for object inheritance models as they apply to tables. This means that we can have parent/child relationships between tables and leverage that to structure out data in meaningful ways. In our example, we will apply this to hydrology data. This data can be points, lines, polygons, or more complex structures, but they have one commonality; they are explicitly linked in a physical sense and inherently related and are all about water. Water/hydrology is an excellent natural system to model this way, as our ways of modeling it spatially can be quite mixed depending on scales, details, the data collection process, and a host of other factors.