River basin is The area of land from which all surface run-off flows through a sequence of streams, rivers and, possibly, lakes into the sea at a single river mouth, estuary or delta
River basin district corresponds to a national river basin district (example: rivers of Corsica)) or a portion of an international river basin district situated on the territory of a Member State (examples: Meuse, Sambre)
River basin district is the main unit for management of river basins and is represented cartographically by the aggregation of sub-basins component.