Headwaters are the source of a river or stream, the literal waters that feed the river. There are a number of ways to define headwaters, and a number of potential sources of water to feed rivers and streams. In some cultures, people have mystical associations with these waters, especially those of major rivers which play a vital role in their communities, and these people may view the place as the source of life for the community as well as the literal source of water for the stream. As a result, shrines are sometimes established at sites identified as headwaters.
One way to think about headwaters is to imagine walking along the banks of a river or stream until it vanished. This furthest point along the river could be considered the headwaters. Some people consider this to be the furthest conceivable point from which water could flow in a watershed, whether or not the place is bearing water, and as a result, the location may move around. Others consider the headwaters to be the furthest point that supplies water throughout the year, making the location a stable, static place.
Many rivers start out as marshes. Others may start with springs and upwellings of ground water that are a bit easier to find and define than a large marsh. It is also possible to find glacial headwaters, those that come from glacier runoff. One concern of scientists who are worried about global warming is that glacier shrinkage may result in the loss of rivers and streams supplied by this source.
Many rivers have an assortment of tributaries, small branches that come together to form the river. As a result, their headwaters may be very diverse and widely dispersed, with some people calling the small streams which come together to make a river headstreams. Looking at a river on a map, people often find that the river looks like a tree, with a thick trunk and many forking branches with even smaller tributaries sprawled out across a drainage basin.
Finding a river's source can be an adventure. Some people like to structure hiking and walking trips around searches for headwaters, because it can make an interesting and fun goal for the trip. When the source of a river ends in a marsh, looking for the source can be rough going, as marshes are often surrounded by dense groundcover and woodland that must be slogged through.