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The Chesapeake Bay is the national treasure. 

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It's one of the most productive estuaries in the world.

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It's the largest estuary in the United States and

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has the largest land area to water volume ratio of any estuary in the US. 

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Which means what happens on the land greatly affects the conditions of the Chesapeake  Bay.

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Landsat is a critical and invaluable tool for characterizing the landscape and 

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characterizing it in terms of mapping impervious surface, mapping it over time. 

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We have satellite imagery for the Chesapeake Bay that covers the entire

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64,000 square miles of the Chesapeake Bay watershed. 

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Unfortunately, the Chesapeake Bay and 90 percent of its title tributaries are impaired. 

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They're impaired with poor water clarity and low dissolved oxygen, as a result of

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excess  nutrients and sediment coming into the bay. 

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 Excess nitrogen and phosphorous and sediment that's draining off the land into the Bay 

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is obscuring the clarity of the water. 

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The nutrients are contributing to increased algal growth. 

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And when those algae die at the bottom of the bay and decompose, they starve the bay of oxygen

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oxygen that living resources need to survive. 

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 The sources of those nutrients and sediments are fertilizers, both manure and chemical fertilizers,

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applied to farmland and applied to residential lawns. 

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It's also from the exhaust from our cars and air pollution from power plants out in the Ohio Valley. 

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Landsat imagery is critical for monitoring changes in impervious surfaces,

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monitoring changes in tree canopy and and then other ground cover like grasses and shrubs. 

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We can use the satellite imagery to track consistently through time across six states

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how the condition of the landscape has changed and what it is like. 

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The Landsat satellite is basically a camera in space,

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and in essence it's actually seven  cameras,

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because it collects the reflection of the sun off the earth's surface

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in seven bands, seven kind of wavelengths. 

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 We use this information to characterize different features on the land

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such as trees or impervious cover

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because each one of these features reflects the sun in different wavelengths. 

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We're able to take the information from the satellite

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 and take what's basically a bunch of numbers

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and translate that into well these numbers correspond to trees

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and these other numbers correspond to impervious surfaces,

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and do that consistently across very large areas. 

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 Landsat is just invaluable in providing this baseline of observations

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 for science about how human activities on the land

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affect water quality, affect wildlife habitat, affect air quality. 

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Without it we wouldn't be able to really understand

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how sources of nutrients and sediment have changed

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and where they are in the Chesapeake Bay.

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