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What Is A Watershed?
Information
taken from EPA's Coastal Watershed Factsheets: http://www.epa.gov/owow/oceans/factsheets/fact1.html
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 water body. In our case, this common body of water is Manhasset
Bay.
Parts of the Coastal Watershed
The coastal watershed has several parts. It
starts up at the beginning headwaters of the streams and rivers
that ultimately drain down to the coastal areas. Headwaters often
include wetlands, and wetlands often are 
adjacent to the flowing waters of rivers or streams. As the streams
and rivers flow to coastal waters, they are influenced by many land
and water uses. They pass through upland areas used for a variety
of purposes such as farming, housing, businesses, recreation, and
conservation. Upon reaching the coastal areas, the rivers empty
into estuaries, which provide a unique habitat for a diverse group
of organisms. Among other habitat functions, rivers and estuaries
provide breeding and feeding grounds for a variety of aquatic and
terrestrial animals. Nearshore waters, the areas directly offshore
from the beach, are part of the coastal watershed because they are
influenced by the activities going on along the shoreline and by
pollutants coming from the land. Farther offshore are coral reefs
(in tropical areas) and other offshore habitats that are part of
the coastal watershed as well.
How Does the Watershed Influence Marine Resources?
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
urbanized and suburbanized 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. Upon
reaching the coast, the stream or river can be affected by commercial
and recreational boating, discharges from industrial and municipal
facilities, and recreational activities on beaches. All of these
areas-- agricultural, uburban, urban, and coastal-- can have an
impact on marine resources.
Some Pollution Impacts on the Coastal Watershed
Soil (loose dirt) from construction
sites, farms, and areas where dirt is exposed can wash off into
streams and rivers when it rains and flow to lakes, estuaries, and
oceans. The result can be muddy waters that smother organisms living
on the bottom, decrease the amount of light reaching the sea grass
beds, and clog fish gills. Some kinds of pollutants can bind to
sediment and flow with it to coastal waters.
Excess
nutrients can also wash off the land when it rains and end up
in coastal waters. Sources of excess nutrients include lawn fertilizers,
pet and farm animal waste, decaying plant material, failing septic
tanks, atmospheric deposition, and inefficient sewage treatment
plants. The loss of wetlands in many watersheds has reduced the
ability of nature to process these nutrients before they enter rivers,
streams, and ultimately estuaries. These nutrients can  cause
an excessive amount of algae (microscopic plants) to grow in the
water, blocking the light reaching sea grass. When the algae die
off, the decaying process uses up the oxygen in the water, leaving
little, if any, for fish and other aquatic organisms. In addition,
some of these algae and related organisms (including Pfiesteria
piscicida) release toxins that can kill fish or shellfish, and
can be harmful, or even fatal, to humans.
Toxic
substances, such as pesticides from lawns, gardens, and farms,
and lead, oils, and greases deposited on roads from cars and trucks,
can all run off the land with rainfall and snowmelt. Industrial
plants and municipal wastewater treatment plants can also contribute
to the amount of toxic substances entering streams and rivers and
ultimately lakes, estuaries, and coastal waters. Fish kills and
loss of the recreational uses of an area can occur.
Pathogens
are microscopic organisms like bacteria and viruses. They come from
untreated or poorly treated sewage, pet and farm animal waste, and
improperly handled medical waste. Pathogens in the water in unsafe
amounts result in beach closures, shellfish bed closures, fish kills,
and human health problems.
Resource Impacts
Activities in the watershed can adversely
affect a variety of resources. (Specific impacts on each of these
resources are discussed in the referenced factsheets.)
Beaches-- Overloading of pollutants
such as sewage and debris can result in beach closings. (EPA 842-F-98-010)
Bays and estuaries-- Pollutants in
and structural alterations to bays and estuaries can lead to loss
of breeding and feeding grounds of fish, other aquatic animals,
and birds, as well as loss of recreational areas. (EPA 842-F-98-009)
Nearshore waters-- Along with bays
and estuaries, nearshore waters are collection places for pollutants
that flow from the watershed. (EPA 842-F-98-007)
Coral reefs and other offshore areas--
Marine debris and pollutants such as nutrients and pesticides can
flow offshore and affect coral reefs and other offshore habitats.
(EPA 842-F-98-008)
It is important to think of the watershed
as a whole system that is tied together. What happens in one part
of the watershed can affect another part, sometimes hundreds of
miles away
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