headwater

This term refers specifically to the geographical origin of a river system. It carries a connotation of purity and untouched nature, often evoking images of remote mountain springs or glacial melts. While it describes a specific location, it is frequently used to describe the entire upper reach of a river basin.

In technical hydrological contexts, the term is often used in the plural form "headwaters" to encompass the collective network of small streams and springs that feed into a main river. While the singular form is grammatically correct for a single source, the plural is significantly more common in academic and environmental discourse.