Editing River source (section)

{{short description|Starting point of a river}}
{{Redirect|Headwater}}
{{refimprove|date=October 2024}}
[[File:wey source farringdon.jpg|right|thumb|upright=1.3|[[River Wey]] near its source at [[Farringdon, Hampshire|Farringdon]], England]]
The '''headwater''' of a [[river]] or [[stream]] is the geographical point of its beginning, specifically where [[surface runoff]] water begins to accumulate into a flowing channel of water. A river or stream into which one or many [[tributary]] rivers or streams flows has many headwaters, these being all of the individual headwaters of its tributaries. Each headwater is one of the river or stream's sources, as it is the place where [[surface runoff]]s from [[rainwater]], [[meltwater]], or [[spring water]] begin accumulating into a more substantial and consistent flow that becomes a [[Strahler number|first-order tributary]] of that river or stream. The tributary with the longest [[channel (geography)|channel]] of all the tributaries to a river or stream, such length measured from that tributary's headwater to its mouth where it discharges into the river or stream, is the [[main stem]] of the river or stream in question.