Factors Impacting Bay and Watershed Health

Chesapeake Bay Health & Restoration Assessment:Executive Summary03/10/09

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Factors Impacting Bay and Watershed Health


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Pollutants


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Nitrogen Loads and River Flow to the Bay

Billions ofGallons of Flow

0

200

400

600

800

1990 1995 2000 2005 20100

25

50

75

100

Data and Methods: www.chesapeakebay.net/status_nitrogen.aspx. 2008 data are provisional.

Nitrogen Loads and River Flow to Chesapeake BayMillions of Pounds

of Nitrogen

River Flow

Average Load


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Phosphorus Loads and River Flow to the Bay

0

20

40

60

80

1990 1995 2000 2005 20100

25

50

75

100

Billions ofGallons of Flow

Data and Methods: www.chesapeakebay.net/status_phosphorus.aspx. 2008 data are provisional.

Phosphorus Loads and River Flow to Chesapeake BayMillions of Pounds

of Phosphorus

Average Load

River Flow


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Sediment Loads and River Flow to the Bay

• Preliminary estimates indicate that 3.3 million tons of sediment reached the Bay during 2008. This is 700,000 tons more than 2007 and 800,000 tons less than the 4.1 million ton average load from 1990-2008.

• The sediment load estimates do not account for sediment from the coastal plain areas of the watershed.

• Scientists are currently developing methods to quantify the total loads of sediment to the Bay.


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Chemical Contaminant Loads to the Bay • Synthetic organic pesticides and their

degradation products have been widely detected at low levels in the watershed, including emerging contaminants such as pharmaceuticals and hormones.

• Fish (principally male bass) in the Potomac watershed have testicular oocytes - female eggs growing in their testes - a form of intersex. Reproductive abnormalities in fish have been strongly linked with a variety of contaminants that affect the endocrine systems of fish.

• Scientists are currently developing methods to quantify chemical contaminant loads to the Bay.


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Land Use


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Bay Watershed Population and Impervious Surface

0

0.2

0.4

0.6

0.8

1

1.2

1950 1960 1970 1980 1990 2000 2010 2020 20300

5

10

15

20

25

Millions of Acres of Impervious Surface Millions of People

Projection

Data and Methods: www.chesapeakebay.net/status_population.aspx

Bay Watershed Population and Impervious Surface

PopulationImpervious Surface


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Bay Watershed Forest Cover

0

20

40

60

80

100

1650 1700 1750 1800 1850 1900 1950 2000

Percent Forest Cover

Data and Methods: www.chesapeakebay.net/status_watershedforests.aspx

Bay Watershed Forest Cover


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Natural Factors


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River Flow into Chesapeake Bay

0

10

20

30

40

50

60

70

80

9019

38

1948

1958

1968

1978

1988

1998

2008

Normal Range

Wet Years

DryYears

Data and Methods: www.chesapeakebay.net/status_riverflow.aspx

Water Year Mean River Flow (billions of gallons per day)


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Weather• Rainfall, temperature and winds have a

great impact on water quality, habitats and fish and shellfish populations.

• Climate change and variability have caused water temperatures in the Bay to exhibit greater extremes during the 20th century than the previous 2,000 years.

• Sea-level rise related to climate change is contributing to the loss of vital coastal wetlands.


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Other Pressures

Factors Impacting Bay and Watershed Health

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