Sauer

The Sauer (German, Luxembourgish) or Sûre (French) is a river in Belgium, Luxembourg and Germany. It is a left tributary of the river Moselle, and so it is part of the drainage basin of the Rhine river.
Geography.
The Sauer river has a length of and a drainage basin with an area of .
Course.
The source of the Sauer is, as Sûre, in the southeast of Belgium in the Ardennes (Luxembourg province), on the western part of the Rhenish Massif, at an altitude of about .
From there, the Sauer flows to the east and crosses the border between Belgium and Luxembourg near Martelange. It forms the border between Belgium and Luxembourg for north of Martelange. On their way through the mountainous north of Luxembourg (the Oesling), it passes through the Lac de la Haute Sure, an artificial lake to the west of Esch-sur-Sûre.
After flowing through Ettelbruck and Diekirch, the Sauer forms the border between Luxembourg and Germany for the last of its course, passing Echternach before joining, as left tributary, the Moselle in Wasserbillig, at about of altitude.