A watershed is a geographic area in which all sources of water, including lakes, rivers, estuaries, wetlands, and streams, as well as ground water, drain to a common surface or water body. Watersheds are defined by the topography of the land.
Since a watershed is made up of several components that are all part of the “big watershed picture,” it is important to remember that what happens on the land can affect the water. For example, if a river or stream flows through an agricultural area, it can pick up fertilizer, manure, and pesticides from farming operations that run off the land after a rainstorm.
As it passes urban and suburban areas, it might gather fertilizers that wash off lawns, untreated sewage from failing septic tanks, wastewater discharges from industrial facilities, sediment from construction sites, and runoff from impervious surfaces like parking lots. All of these land uses – agricultural, suburban, urban, and coastal –can have an impact on our fresh and marine waters. (Excerpted from the US EPA Office of Water, Publication EPA 842-F-98-006, “Your Coastal Watershed”)
Monterey Bay Watersheds
The central coast of California has over 11 watersheds which drain into the Monterey Bay National Marine Sanctuary, the nation’s largest protected marine area and the second largest protected marine area on the earth (after the Great Barrier Reef in Australia). The Sanctuary’s boundaries stretch 350 miles from Marin County to San Luis Obispo County, covering over 1/3 the coast line of the state and extending as far as 53 miles offshore. The sanctuary has been in place since 1992 (Monterey National Marine Sanctuary).