Examples of the possessive form of plural nouns: actors - the actors' dressing rooms. bottles - the bottles' labels. children - the children's playground. doctors - the doctors' offices. eggs - the eggs' carton. friends - my friends' names. geese - the geese's pen.
This covered pool is really a good example of a watershed. The blue cover represents the watershed, the area in which precipitation that falls flows down-gradient towards the lowest part of the basin, the center of the pool cover in this case. Likewise, in nature, water flows towards a valley, river, or lake.
Drainage Basin / Watershed. The precipitation that falls into a valley, and on surrounding interfluves flows downward usually creating a stream or river. The area of land that contributes water to a stream or river is called a watershed, or drainage basin. Small drainage basins generally contribute to streams, while the water from larger drainage basins come together to form large rivers.