What is the natural removal of water from an area known as?

The natural removal of water from an area is referred to as drainage. This process involves the movement of water, typically from rain or natural bodies of water, away from a specific area through various channels, like rivers or streams, or via absorption into the ground. Drainage is critical for preventing waterlogging, managing flood risks, and maintaining the health of ecosystems by ensuring that water does not remain stagnant, which can lead to problems such as erosion or habitat loss.

Other concepts mentioned in the choices are related to water but do not specifically define the broader process of moving water out of an area. Water flow can describe the movement of water in general, hydration refers to the process of absorbing water, and evaporation is the transformation of water from liquid to vapor, which is a different process entirely. Therefore, drainage is the most accurate term to describe the natural removal of water from an area.