Awatershed is
an area where all water drains into the same river system
the start of a river system
the location where tributaries form rivers
a depression left by glaciers which forms a lake

Another word for "watershed" is drainage basin - it refers to all the land that will end in the same river and it's separated from land which will provide water for other rivers (but sometimes this separation is also called watershed- this can be confusing!)

so the correct answer is
an area where all water drains into the same river system

Could  i have the map?

The telegraph idk what else to tell you you are probably just gonna copy it which btw i would do the same thing but it says i have to have at least 20 characters so yeah there you go