A natural geo-hydrological unit of land that collects water and drains it through a common point by a system of streams is called a:

A watershed is a natural geo-hydrological unit of land that collects water and drains it through a common point via a system of streams. The Amazon Basin is the largest watershed in the world. For comparison:
- A reservoir is a large lake where water is stored for use by a particular area or city
- An aquifer is an underground layer of porous or permeable rocks that store and retain groundwater
- Warabandi is a rotational water supply system based on predetermined schedules according to area and crop needs