The source of a river or stream is the place from which the water in the river or stream originates. The River Wey in Surrey, Hampshire and West Sussex is a tributary of the River Thames with two separate branches which join at Tilford Farringdon is a village in the East Hampshire district of Hampshire, England. Wildlife Hampshire has wildlife typical of the island of Great Britain "Riverine" redirects here For the use of that term in Maritime geography, see there A stream is a body of Water with a current, confined within a bed and stream-banks Water is a common Chemical substance that is essential for the survival of all known forms of Life.
More specifically, a source is defined as the most distant point (from the river mouth) in the drainage basin from which water runs year-around, or, alternatively, the furthest point from which water could possibly flow. "Riverine" redirects here For the use of that term in Maritime geography, see there A drainage basin is an extent of Land where Water from Rain or Snow melt drains downhill into a body of water such as a River,  This latter definition includes sometimes-dry channels and removes any possible definitions that would have the river source "move around" from month to month depending on precipitation or ground water levels. This definition, from geographer Andrew Johnston of the Smithsonian Institution is also used by the National Geographic Society when pinpointing the actual source of rivers such as the Amazon or Nile. The Smithsonian Institution (smɪθsoʊnɪən is an educational and research institute and associated Museum complex administered and funded by the Government of Overview The NGS's historical mission is "to increase and diffuse geographic knowledge while promoting the conservation of the world's cultural historical and natural
Other authoritative geographic definitions agree, stressing that a river source is never a confluence but is "in a location that is the farthest, along water miles, from where that river ends. Confluence, in Geography, describes the meeting of two or more Bodies of water. " 
Thus, neither a lake (except in rare cases in which it has no inflows) nor a confluence of tributaries can by definition ever be a true river source, though both often provide the starting point for the portion of a river carrying a single name. For example, National Geographic and all other major geographic authorities and atlases define the source of the Nile River not as Lake Victoria's outlet where the name "Nile" first appears, but as the source of the largest river flowing into the lake, the Kagera River. The Nile (النيل, Ancient Egyptian iteru or Ḥ'pī, Coptic piaro or phiaro) is a major north-flowing River Lake Victoria or Victoria Nyanza (also known as Ukerewe and Nalubaale) is one of the Great Lakes of Africa. The Kagera River, also Akagera River, is a remote source of the Nile.
The official source of the Mississippi-Missouri is not where either river begins in name, but is defined by the USGS as the source of the longest tributary, the Jefferson River The official source of the Amazon River is a similar example. This is a list of the longest rivers on Earth. It includes river systems over 1000 kilometers The United States Geological Survey ( USGS) is a scientific agency of the United States government. The Jefferson River is a Tributary of the Missouri River, approximately long in the U The Amazon River (Rio Amazonas Río Amazonas of South America is the largest river in the world by volume with a total river flow greater than the next top ten largest rivers 
Often the source, or start of the most remote tributary, may be in an area that is more marsh-like, in which the "uppermost" or most remote section of the marsh would be the true source. In Geography, a marsh, or morass, is a type of Wetland which is subject For example, the source of the River Tees is marshland. The Tees is a river in Northern England. It rises on the eastern slope of Cross Fell in the Pennines, and flows eastwards for about 85 miles In Geography, a marsh, or morass, is a type of Wetland which is subject
The furthest stream is also often called the headstream. Headwaters are usually small streams that are often cool waters, because of shade and recently melted ice or snow. They may also be glacial headwaters, waters formed by the melting of glacial ice. "Glacial" and "Glaciation" redirect here For the geological periods see Glacial period. Ice is a Solid phase, usually crystalline, of a Non-metalic substance that is liquid or gas at Room temperature, such as Ammonia
The source is the farthest point of the river stream from its estuary, mouth, or its confluence with another river or stream, regardless of what name that watercourse may carry on local maps and in local usage. An estuary is a semi-enclosed Coastal body of Water with one or more Rivers or Streams flowing into it and with a free connection to the open Confluence, in Geography, describes the meeting of two or more Bodies of water. Where a river is fed by more than one source, it is customary to regard the longest as its source, with other sources considered tributaries. A tributary is a Stream or River which flows into a mainstem (or parent river Often, however, the manner in which streams are named is not consistent with this convention. Many rivers change names numerous times over their length.
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. The volumetric flow rate in Fluid dynamics and Hydrometry, (also known as volume flow rate or rate of fluid flow) is the volume of fluid which Surface runoff is a term used to describe when soil is infiltrated to full capacity and excess Water, from Rain, Snowmelt, or other sources flows
Headwaters are the most extreme upstream areas of a watershed. The end point of the watershed is called an outflow or discharge. A drainage basin is an extent of Land where Water from Rain or Snow melt drains downhill into a body of water such as a River, A watershed is an area of land that is drained by a body of water. The river source is generally on or quite near the edge of the watershed, or watershed divide.
The word "source", when applied to lakes rather than rivers or streams, refer to the lake's inflow. A lake (from Latin lacus) is a Terrain feature (or Physical feature) a body of Liquid on the surface of a world that is localized to the In Hydrology, the inflow of a Body of water is the source of the Water in the body of water