Xiaojie Yang

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ISP217L 004

Dec 4

Lab 5

Water and the EnvironmentLaboratory ISP 217L
Lab Write-Up Assignment
Fall 2015

How does human activity inwatersheds affect the quality of lakes and rivers?

  1. The watershed that has the most human development/activity

  1. The watershed that has the least human development/activity

Use different colors or fillpatterns to differentiate the land use categories, but use the samescheme for both charts. Hint: the different categories may not sum toexactly 100%: you can create an “other” category to make up thedifference (this is what the “other” space is for in your Exceltemplate). You can also re-size the graphs so they both fit on onepage to ease comparisons across the watersheds.

ii. Produce three scatter plotsas follows: [3 pts each]

  1. Plot 1: plot % agriculture against one water quality variable of your choice.

  1. Plot 2: plot % forest against one water quality variable of your choice.

  1. Plot 3: CHOOSE % urban or % open field or % wetland and plot it against one water 
quality variable of your choice. Pick a relationship here that interests you most or 
surprises you!

All 3 scatterplots should have: atrend line, its equation, and R2. Hint for the scatter plots: thinkabout which variable belongs on which axis, the number of points eachgraph should have, and what each individual point represents!

iii. Compute the correlationcoefficient (r) for the relationship between total phosphorus (TP)and chlorophyll-a (chla), using Excel. This number will be used inyour answer to Question 5 below.


Mean total phosphorus (µg/L)

Mean chlorophyll a (µg/L)

Mean total phosphorus (µg/L)


Mean chlorophyll a (µg/L)



B. Questions

  1. State your hypothesis (es). Do the data support or reject your hypothesis (es)? [2 pts]

Null hypothesis: Humanactivity in watersheds affect water quality in lakes and rivers

Researcher hypothesis: Humanactivity in watersheds do not affect water quality in lakes andrivers

  1. Interpret your pie charts [3 pts]

a. What watershed has thegreatest level of human activity?

The watershed with the most human activity is the Lake Christianawatershed

b. What watershed has the least?

The watershed with the leastis Moon Lake watershed.

c. What land covers/uses areprevalent in each case?

Agriculture hasthe human activity largest level at 67.17% in Christiana Lake

Forest is thedominant land cover class in the Moon Lake watershed with 89.22%

  1. Interpret your scatterplots [4 pts]

    1. What is the relationship between agriculture land use activity and the lake water quality 
variable? Refer to the R2 values

The increase use of land foragriculture leads to poor quality of lake water

Increased agriculture isassociated with decreased Secchi depth and this indicates less clearwater or poor water quality

The R^2 value of 0.50 indicatethat there is a strong relationship between agriculture % and Secchidepth.

    1. What is the relationship between forest (natural) land cover and the lake water quality 
variable? Refer to the R2 values

Thecontinuous use of the land for forest creates an improvement of waterquality. Forest acts to absorb the excessive phosporus and otherdebris before they reach the lake thereby increasing the quality ofwater.

    1. What is the relationship between the land use/cover variable of your choice and the lake 
water quality variable? Refer to the R2 values

The increase use of land forurban development increases the phosphorus content in lake watermaking its quality to go down. The 0.396 of R2 values indicate thatland for urban development determines phosphorus content by 39.6%

ISP 217L Lab 5 Assignment Page 1

  1. Why is it important to consider multiple water quality metrics and multiple years of water quality data when making an assessment of a lake’s condition? [3 pts]

This would remove bias andincrease reliability of the results that can be achieved after arepeat study..

    1. Why might there be some variation in the measurements from a single lake from year to year?

The variation might be broughtout by the timing of the tests and the accuracy of the equipmenttogether with the change in the non-controllable variables such asthe urban development or the farm inputs used in agriculture fields.

    1. How can we best deal with that variation when making a determination of the lake’s water quality?

Theresearcher should put some allowance to accommodate the variationsusing the assumptions that are relevant and use several years to evenout the variations.

  1. Is there a correlation between nutrient concentrations (Total Phosphorus) and algae abundance (Chlorophyll-a) in the lakes? [3 pts]

    1. Provide the correlation coefficient (r) and explain exactly what it tells you about the strength and directionality of the relationship.


The correlation indicates thatthere is a strong relationship that is positive. The increase innutrient concentrations leads to an increase of algae abundance

    1. Does your correlation analysis make sense biologically?

There is biological sense madeby correlation analysis. Phosphorus is required for the groth of thealgae but the extra increase by human activities leads to eccessiveincrease in algae that chocks the sun sunlight penetration to seabed. When algae die they discompose therby using large amount ofoxygen depriving it from other animals.

    1. What do the findings imply about the steps required to manage and ameliorate 

There is need to ensure thatthe increase of phosphorus is controlled to curb the increase of thealgae population because it lead to changing of the watershed in thelake ecosystem and disrupt the food web for native communities.

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