Photo Credit: www.depweb.state.pa.us/justforkids
A watershed is a geographic region: an area of land drained by a river and its tributaries to a common outlet. A watershed also represents a connection between all of the people and activities found within its boundaries. In hydrology, the watershed is the unit of focus for studying the movement of water.
Groundwater is part of the watershed but the underlying aquifer often does not have the same boundaries. A portion of the water that enters the aquifers beneath the watershed may flow towards an adjacent watershed because groundwater flow paths do not always match those of their overlying drainage network. See more information on our groundwater page.
John Welsey Powell, Civil War veteran, geologist, early river explorer and the second Director of the U.S. Geological Survey, is the father of the watershed concept. He had some interesting thoughts on why the west should have been settled according to watershed boundaries. For excerpts from his writings please click here.