The Rhine river basin is dealt into nine – mostly international - sub-basins, all depending on hydrographical and natural characteristics. The main stream Rhine and its tributaries have been divided into six sections (Alp Rhine / Lake Constance, High Rhine, Upper Rhine, Middle Rhine, Lower Rhine, Delta Rhine). The three largest tributary areas – Neckar, Main and Moselle-Saar are separate units. In these sub- basins the different countries and German Länder involved or the regions concerned agree upon all questions relating to water management on a transboundary level.
The water quality and ecology of the R. Aare is being coordinated in the area of operation High Rhine.