the.com/catchment
The land's way of deciding which raindrop becomes whose river.
means The entire area of land from which rainfall drains into a particular river, lake, or reservoir.
from Built from catch plus the suffix -ment, coined by 19th-century engineers tracking exactly where water gets caught and carried.
Also calledWatershed in America, drainage basin everywhere else.
Invisible bordersDivides follow ridgelines, not human maps.
Modern reuseSchools borrow it for enrollment zones.