in the Swiss canton of Graubünden is generally regarded as the source of the Rhine. Its outflow is called Rein da Tuma and after a few kilometers, it forms the Vorderrhein/Rein Anteriur. The course of this river is not particularly representative, after about two kilometers, its water is diverted into Curnera reservoir. The water is released at the Tavanase plant and flows into the Rhine at Ilanz. The river begins to be called Rhine in the vicinity of Chur, more specifically, at the confluence of the Vorderrhein and Hinterrhein/Rein Posteriur next to Reichenau in Tamins.
There are different criteria for the definition of tributaries, and by some definitions, irrespective of the official name, one strand or another may be called the source. Determining the source of the Rhine is difficult, because in the river system of the Anterior and Posterior Rhine, there are many headwaters of similar size. Apart from the common criterion of the larger discharge, ongoing cartographic research allows us to determine the headwater with the greatest length, the largest catchment area or the highest source. The direction of flow may be crucial to the nomenclature as may be the significance of the valleys as room for housing and transport. Both criteria are more appropriate to the Vorderrhein, since the Hinterrhein valley was hardly populated before the influx of the Walser.
Rhine sources by name
The Swiss Federal Office of Topography and ETH Zürich indicate a point north of Lake Toma and the Rein da Tuma as the source of the Rhine, and as the source of the Hinterrhein a point in the upper valley of the Rheinwald, east of the Rheinwaldhorn. In the area of the headwaters of the Rhine, the term Rhine is used as part of the name of many rivers, in many different spellings, such as Rhine, Rein, Rain, Ragn, Ren, Reno and Rin.
Size of the catchment areas
The catchment area of the Vorderrhein covers about 1512 km²; the basin of the Hinterrhein, is slightly larger at 1693 km². The percentage of precipitation flowing down the river is fairly similar in the valleys of the headwaters of the Rhine, so the size of the catchment area tends to be proportional to the average discharge, and therefore this criterion does not need to be considered separately.
Summary
No clear hierarchy can be established among the headwaters of the Rhine. The two main systems, the Vorderrhein in the west and the Hinterrhein in the south and east, differ only slightly in length, discharge and size of their catchment areas. The longest paths begin in the upper Surselva and the upper Landwasser Valley, respectively the most western and the most eastern parts of the headwaters area. The source of the hydrological main path would be found in the east, in the Dischma.
