A catchment area, or the people it serves.
Any structure or land feature which catches and holds water; the collection of such water.
To divide into catchment areas.
An area which drains itself into a river.
An elongated depression cast between hills or mountains, often garnished with a river flowing through it.
Any structure resembling one, e.g. the interior angle formed by the intersection of two sloping roof planes.
To form the shape of a valley.