What do we call the total area from which a river collects its water?

The term "drainage basin" is used to describe the total area from which a river collects its water. It encompasses all the land where precipitation collects and flows downhill, eventually contributing to the river and its tributaries. This area is essential for understanding how a river system operates, as it highlights the geographical features, ecosystems, and communities that are affected by the river's flow.

The drainage basin includes various smaller areas, which can be referred to as watersheds, but the drainage basin itself represents the larger system that channels water into the river. This terminology is crucial for studies related to hydrology, ecology, and environmental management, as it helps in identifying how water resources and landscapes are interconnected. In this context, the source is where a river begins, and tributaries are smaller streams or rivers that feed into the main river, but they do not represent the overall area of water collection.