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What is a Watershed?
A watershed is..."that area of land, a bounded hydrologic system, within which all living things are inextricably linked by their common water course and where, as humans settled, simple logic demanded that they become part of the community." -- John Wesley Powell, scientist and geographer
No matter where you are or where you live, you are in a watershed. A watershed is an area of land that catches rain and snow and drains it into a body of water, such as a river, pond, estuary, bay, lake, or ocean. A watershed can also be called a drainage basin.
"Watershed" is the term used to describe the geographic area of land that drains water to a shared destination. The drainage system (and the watershed) also includes the geographic area surrounding the stream system that captures precipitation, filters and stores water, and determines water release into stream systems. The stream system is the visible, aboveground portion of a larger drainage system. A watershed, therefore, is "an area of land that drains water, sediment, and dissolved materials to a common outlet" (FISWRG 1998).
Any activity that changes soil permeability, vegetation type or cover, water quality, quantity, or rate of flow at a location can change the characteristics of a stream or even the watershed at downstream locations. Land use practices such as clearing land for timber or agriculture, developing and maintaining roads, housing developments, and water diversions may have environmental consequences that greatly affect stream conditions even when the land use is not directly associated with a stream. Proper planning and adequate care in implementing projects can help ensure that one activity within a watershed does not detrimentally impact the downstream environment.
In recent years, watersheds across the United States have become a focal point for community-based environmental conservation. Through the collaborative efforts of watershed groups – consisting of the people living and working within each watershed – major improvements in water quality, fisheries enhancement, wildlife habitat, and overall quality of life have been accomplished. A watershed provides water for drinking, recreation, and agriculture, and is a rich source of biological diversity that includes habitat for many threatened and endangered species, including salmon and trout. Coho salmon (Oncorhynchus kisutch) and steelhead trout (O. mykiss) return from the ocean and travel upstream to reach spawning grounds deep within the watersheds in Napa County. Spawning success depends upon good environmental conditions to ensure the survival of the next generation of salmon.
Source: Circuit Rider Productions, Inc. and National Oceanic and Atmospheric Administration Coastal Services Center. 2004. Salmonid Habitat Restoration Planning Resource for San Mateo and Santa Cruz Counties [Website]. Available at: http://www3.csc.noaa.gov/salmonid/index.htm.
Reference: Federal Interagency Stream Restoration Working Group (FISWRG). 1998. "Stream Corridor Restoration: Principles, Processes, and Practices." GPO Item No. 0120-A; SuDocs No. A 57.6/2:EN3/PT.653. View on-line document.
Watercolor by Jenny MacIlvaine
