SOURCE (RIVER OR STREAM)

'Headstream' is the origin of water flow that initiates the subject watercourse. It is the start of the river or stream.
The 'source' of a river or stream may be a lake, a marsh, a spring, glacier, or a collection of 'headwaters'. For example the source of the River Tees is marshland. The furthest stream is called the 'headstream'. Headwaters are usually small streams that are often cool waters, because of shade and recently melted ice or snow. Also they may be 'glacial headwaters', waters formed by the melting of glacial ice. The source is normally the farthest point of the river stream from its estuary or its confluence with another river or stream.
Where a river is fed by more than one source, it is customary to regard the highest as its source, with other sources considered tributaries. Often, however, the manner in which streams are named is not consistent with this convention.
Near its source, a river or stream may have a modest flow rate, but the flow increases as more surface runoff and tributaries drain into the subject stream.
Headwaters are the most extreme upstream areas of a watershed. The end point of the watershed is called a outflow or discharge.
A watershed is an area of land that is drained by a body of water.