What defines a watershed?

A watershed is defined as a total land area contributing runoff to a waterway. This means that any precipitation that falls within the boundary of the watershed will eventually flow into the waterway, whether it is a stream, river, lake, or any other body of water. The concept of a watershed is critical for understanding water quality and hydrology, as the land and activities within the watershed can significantly affect the water that gathers in these waterways.

The other options do not capture the complete essence of what a watershed is. A low-lying area where water collects may describe a pond or a depression, but it does not encompass the broader land area that drains into a waterway. Heavy rainfall can occur in various places, but not all of these areas make up a watershed. Lastly, while a wetland ecosystem is important in terms of environmental health and water filtration, it is just one type of habitat that might exist within a watershed rather than a definition of the watershed itself. Thus, the defining characteristics of a watershed relate specifically to the drainage area that contributes to a waterway.