Answer Sheet
Land Use Impact on Water Quality
Part 1
1. Describe the spatial patterns of measured phosphorous in 1991. Is there a pattern
by State/ Province? By size of the tributary?
• Larger tributaries have higher raw phosphorous
• There is more phosphorous in Vermont and Quebec than in New york
2. How is the spatial pattern of 1991 phosphorous levels different when we divide
by area? Why is it important to consider the area of a tributary when we are
looking at phosphorous measures?
• Particular tributaries stand out: Rock, Pike, Mill, Stevens, Indian Brook,
LaPlatte, Mettawee, and low levels in New York stand out even more
• Larger drainage areas causing higher phosphorous is a given and we want
to factor that out to find out what has high phosphorous per given area.
3. Why might a Resource Manager want to see data normalized by area or not
normalized by area?
• Tell different stories- highest contributing tributaries versus highest
contributing per hectare.
• Raw tributary data may correspond better to phosphorous levels in parts of
the lake, but normalized data more important for policy considerations.
4. Which tributaries have stayed consistently high in phosphorous measures across
the years? Which have stayed consistently low? (Hint: use the identify tool to get
the names of those tributaries and compare the data.)
• Pike, Missisquoi, Mettawee- consistently high
• Saranac, Salmon, Ausable- consistently low
5. For the 1991 phosphorous measures data choose equal interval as the
classification method. Move your class number up to 30 or higher. Which
tributary becomes highlighted?
• Rock
6. Now change the method to quantile and the number of classes to 4. This breaks up
the data so that there are an equal number of tributaries of each color. This way
we can easily see the top 25% percent and the bottom 25%. Where are the lowest
phosphorous values grouped? Why is it important to know the top 25% and
bottom 25%?
• New York -Adirondack Park area
• Answers will vary for why important- for policy, for analysis, etc.
7. Now choose standard deviation as the classification method. You can change the
colors on the color ramp to a color scheme which makes sense to you. This
classification method applies the data to a bell curve, and highlights the outliers
that are far away from the average phosphorous measure. Which color schemes
best highlight these outliers?
• Answers will vary- something which goes from a dark/ saturated color
through a neutral, to another dark/ saturated color.
8. Which classification scheme do you find most useful for visualizing the 1991
phosphorous data and why?
•
Answers will vary- why is important for explanation of what pattern they
want to show
9. How might a resource manager portray the data? How might a policy maker
portray the data and why?
• Answers will vary- look for understanding how different data displays
suggest different interpretations.
Part 2
10. What areas in the watershed have a higher percentage of forest? What areas stand
out as having a high percentage of agriculture?
• New York has higher forest
• Agriculture high in northern tributaries and Addison County
11. What patterns do you notice between the land use and the phosphorous levels?
Are there tributaries which don’t follow this pattern well? Where are they?
• High and Midphosphorous loads come from high percent agriculture and
percent urban
• Lower phosphorous loads come from heavily forested areas
• Answers will vary for tributaries that don’t follow pattern depending on
data display, but may include Bouquet, East, Mississquoi, Lamoille,
Winooski
12. Why are phosphorous estimates useful? Who might use these estimates?
• Help estimate phosphorous loading in different geographies- like by town
• Help correlate with land use
• Resource Managers, Policy Makers, Scientists, etc.
13. Describe the pattern between the 1992 Land Use and 1992 Phosphorous
estimates.
• High agriculture/ urban produced high phosphorous estimate
• High forest produces low phosphorous estimate
14. What type of phosphorous loading comes from areas with a large increase in
urban land and decrease in agricultural land? Where are these areas?
• Moderate/ average phosphorous load. Specifically in Otter, Winooski,
Lamoille
• Mississquoi is the exception.
• (This data on land use change was actually prepared to better estimate
phosphorous loading from agricultural sources- and demonstrate urban
land use has a higher impact on phosphorous loading than previously
thought).
Part 3
15. What is the predominant type of land use for towns significantly below the
average phosphorous load per hectare?
• Forest
16. Where are towns below average clustered?
• New York- Adirondack Park, as well as other clusters on Vermont and
Quebec on edge of watershed
17. Describe each of the areas with significantly high phosphorous loading. What
general area or towns have high phosphorous loading? What is the predominant
land type contributing to the phosphorous loading in each of these areas?
• In Rock Area- high agriculture
• Northern Vermont- moderately high agriculture
• Greater Burlington- high urban
• Ferrisburgh/ Vergennes- high agriculture
• Granville? – high forest (possible data error?)
• Queensbury/ Glens Falls- high urban
• Plattsburgh- moderately high urban, moderately high agriculture
18. What types of land use may be contributing to phosphorous loading in your area?
• Answers dependent on location