The source of a river, the set of streams that feed into the river's beginning.(noun)
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Use "headwaters" in a sentence
"Needless to say he spent a lot of time bent double under the foliage dapping in headwaters 4 feet wide."
"A watershed is the area representing all the land draining moisture from the highest elevations, usually referred to as the headwaters, to a specified outlet point."
"Right now, the headwaters are the meetings that were held last Tuesday, the party leadership that those delegates will select, and what the newly elected precinct committee people do between now and the 2012 to reach out in their neighborhoods."