I
\
&
%
LU
o
^ PRO^C
Fact Sheet
Chesapeake Bay Water Quality
Chesapeake Bay Program
A Watershed Partnership
Water quality is the most important measure of the Chesapeake Bay's health. For the Bay
to be healthy and productive, the water must be safe for people and must support aquatic
life, such as fish, crabs and oysters. The water should be fairly clear, have enough
oxygen, contain the proper amount of algae and be free from chemical contamination.
Excess nitrogen, phosphorous and sediment lead to murky water and algae blooms, which
block sunlight from reaching bay grasses and create low levels of oxygen for aquatic life,
also known as hypoxia. In 2008, water quality was again very poor, meeting only 21
percent of the goals established in the Chesapeake 2000 Agreement, the same as 2007.
Dissolved Oxygen
Mid-Channel Clarity
Chlorophyll a
Chemical
Contaminants
Water Quality
21%
OF GOALS ACHIEVED
10
20
30
40
50
60
70
80
90
100
Sources of Pollution
Currently the Bay and its rivers receive too much nitrogen, phosphorus and sediment for
the ecosystem to remain healthy. The main sources of these pollutants are agriculture,
urban and suburban runoff, wastewater, and airborne contaminants.
Nitrogen	Phosphorus	Sediment
Urban/
Suburban
28%
Agriculture
72%
Wastewater loads based on measured discharges; the rest are based on an average-hydrology year.
Does not include loads from direct deposition to tidal waters, tidal shoreline erosion or the ocean.
Data and Methods: www.chesapeakebay.net/status_reducingpollution.aspx
Urban/
Suburban
. 16%
Agriculture
42%
Wastewater
20% /
Atmospheric
_ 22%
Urban/
Suburban
32%
Agriculture
46%
Wastewater
. 22%
1

-------
Agriculture
Agriculture covers about 25 percent of the watershed, representing the largest intensively
managed land use. There are an estimated 87,000 farms covering about 8.5 million acres.
Agriculture is the number one source of pollution to the Bay. Improperly applied
fertilizers and pesticides flow into creeks, streams and rivers, carrying excess nitrogen,
phosphorus and chemicals into the Chesapeake Bay. Tilling cropland and irrigating fields
can cause major erosion. Additionally, the nutrients and bacteria found in animal manure
can seep into groundwater and runoff into waterways.
Urban and Suburban Runoff
Human development, ranging from small subdivisions to large cities, is a major source of
pollution for the Chesapeake. Runoff from urban and suburban lands is increasing due to
the region's continued population growth and related construction. Impervious surfaces
such as roads, rooftops and parking lots do not let water penetrate, and runoff carries
pollutants including lawn fertilizer, pet waste, chemicals and trash into waterways.
Developed areas also split up forests, decreasing their filtering capacity. Finally, onsite
wastewater or septic systems release nitrogen that eventually ends up in the water.
Wastewater
There is a tremendous volume of sewage that must be processed in the watershed. The
technology used by the 483 major municipal and industrial wastewater treatment plants
has not removed enough pollution, particularly nitrogen and phosphorus. Upgrading these
facilities so they can remove more pollution from the water is extremely expensive and
takes time. While there has been significant progress in improving treatment at many
wastewater plants, numerous facilities still use old technology. Population growth is
increasing the need for wastewater treatment, causing some facilities to be expanded.
Airborne Contaminants
When pollution is released into the air, it eventually falls onto land and water. Even
larger than the Chesapeake Bay's watershed is its "airshed," the area from which
pollution in the atmosphere settles into the region. This airshed is about 570,000 square
miles, or seven times the size of the watershed. Nitrogen and chemical contaminants -
such as mercury and PCBs - from air pollution contribute to poor water quality in the
region, and about half of these pollutants come from outside the watershed. Air pollution
is generated by a variety of sources, including power plants, industrial facilities, farming
operations and automobiles and other gas-powered vehicles.
(Last Updated: 7/24/09)
2

-------