It's call divide or watershed.
land
A divide
A watershed is the area separating two different drainage basins/river systems.
A divide
Yes, it is correct.
watershed
17 river basins GO NC!!
Trans-pecos, meaning "across the river"
the main river and all of its tributaries are called a river system. The land drained by the river system is called a drainage basin. Drainage basins are separated by the high land in between, known as a divide or watershed.
A ridge of land separating river systems is called a water shed. Normally the land is very high up and mountainous.
the area from which water drains into a river is called the river's catchment. A river's watershed is the connecting ridges surrounding the watershed, and separating it from adjacent ones.
There isn't a river running on the border and separating separating France and Belgium, but there are several rivers flowing from France and into Belgium: Yser, Escaut (called Schelde in Belgium), and the Meuse river.