Ill (France)

The Ill is a river in France. It flows through the plain of Alsace. It is an important left tributary of the Rhine river. It is the main river of Alsace. It flows through the Haut-Rhin and the Bas-Rhin departments in the Grand Est region.
Geography.
The Ill river is long. Its drainage basin has an area of .
Course.
The Ill starts in the northern side of the Glaserberg mountain, in the Jura Mountains near the Swiss border, in the "commune" of Winkel, (Haut-Rhin department), at an altitude of about . From here, the Ill flows first to the east to Ferrette and to Illfurth where it is joined by the "Largue" river, the main right tributary of the Ill.
From Illfurth, the Ill runs northward through Alsace, flowing parallel to the Rhine river. 
The Ill river flows within the Grand Est region, 2 departments and 70 "communes". It flows through the following "communes", among others:
Five "communes" in the Alsace have their names from the riverː
Finally, the Ill river flows into the Rhine river in the "commune" of Offendorf, just to the north of Strasbourg.
Main tributaries.
The main tributaries of the Ill river are all left tributaries; the right tributaries are very short streams. Only the Largue starts in the Jura Mountains; the rest have their sources in the Vosgues mountains, to the east.
Hydrology.
Its average yearly discharge (volume of water which passes through a section of the river per unit of time) is at Strasbourg in the Bas-Rhin department, for the period 1974 - 2017.