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Water: Office of Wetlands, Oceans & Watersheds

Water Quality Facts

We encourage you to visit EPA’s Web sites to learn as much as possible about water quality issues before picking up your video camera.  Below are some key facts about water that may be useful as you begin your research for the EPA Water Quality Video Contest.

Water Quality 

  • About 44% of assessed stream miles, 64% of assessed lake acres, and 30% of assessed bay and estuarine square miles are not clean enough to support uses such as fishing and swimming.
  • Leading pollutants in our nation’s waters include bacteria, mercury, nutrients such as phosphorus and nitrogen, and low levels of dissolved oxygen, which often caused by the decomposition of organic material.
  • Leading sources of pollution in our nation’s waters include air deposition, agricultural runoff, and hydrologic modifications such as water diversions and channelization of streams.
  • A recent study of the nation's streams found that only 28% have healthy biological communities compared to best possible conditions in their region

Urban Runoff

  • Storm water from streets, parking lots, and otherpaved surfaces (known as urban runoff) carries pollution directly into our waters
  • The impervious surface of a city block can generate five times more runoff than a wooded area of the same size.
  • In a natural environment, 50% of the rain fall is absorbed in the ground, 40% is evapotranspired  and 10% runs off; in an area of 75%-100% impervious surface (such as many urban areas) 15% of the water is absorbed in the ground, 30% is evapotranspired and 55% runs off.
  • When it rains, sediment, oil, grease, toxic chemicals from motor vehicles,pesticides and fertilizers from lawns, pathogens and bacteria from pet waste and leaking septic systems, road salts and heavy metals run off city streets untreated into our rivers, lakes, and bays.  

Nutrient Pollution and Hypoxia

  • Agricultural runoff is also one of the leading sources of water impairment for rivers and streams, estuaries, and lakes (reference).
  • The increased use of nitrogen, phosphorus and other nutrient fertilizers in the Mississippi River Basin has led to an increase in the amount that is washed down the Mississippi River and eventually ends up in the Gulf of Mexico (reference).
  • The increase of nutrients leads to large algal blooms. When the algae eventually die and decompose, this dramatically reduces the amount of dissolved oxygen in the water creatinghypoxic zones, more commonly called “dead zones,” in which organisms cannot survive. (reference
  • The Gulf of Mexico “dead zone” is the second largest in the world and persists from summer to early fall there are also smaller dead zones around the coast of the US, including Long Island Sound and Chesapeake bay and over 400 identified in the world. (reference  Exit EPA Disclaimer )
  • In 2008 the Gulf of Mexico dead zone was estimated to be 7,988 sq. miles, roughly the size of New Jersey. (reference  Exit EPA Disclaimer )


  • More than one-third of the United States' threatened and endangered species live only in wetlands, and nearly half use wetlands at some point in their lives. Many other animals and plants depend on wetlands for survival. (Reference)
  • Wetlands provide substantial flood and storm water control. (reference)
  • Wetlands make a significant contribution to water quality and availability including: recharging groundwater aquifers, filtering surface water runoff, they are natural carbon dioxide reservoirs that capture atmospheric carbon, and are also a source of wastewater treatment. (reference)
  • Since colonial times over half of the wetlands in the conterminous United States have been destroyed. (reference)
  • Despite a trend that indicates a slight increase in wetland acreage nationwide, the United States lost an estimated 59,000 acres of vital wetlands annually between 1998 and 2004 in coastal watersheds of the Eastern U.S. (Atlantic, Great Lakes, and Gulf of Mexico). (reference)

Marine Debris

  • Marine debris is any persistent solid material (e.g., plastic grocery bags, soda cans, plastic bottles, cigarette butts, fishing line, etc.) that is directly or indirectly disposed of or abandoned into the aquatic environment.
  • Trash that is not properly disposed of can wash into storm drains or get blown into rivers, streams, and coastal waters and become marine debris.
  • Marine animals such as seals, sea turtles, birds, and fish can be wounded, strangled, or unable to swim if they consume or become entangled in marine debris.
  • Marine animals can swallow marine debris causing suffocation or starvation. Sea birds have been known to swallow small plastic pieces (which look like fish eggs); and sea turtles have been known to swallow clear plastic bags (which look like jellyfish).
  • Marine debris can threaten public safety and hurt the economy with costly cleanups and deterred tourism.

For more information about these and more topics explore our Website.

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