Conductivity
in Ice Lake
Group
Names: ________________________________________________
Date:
_______________________
Knowledge
Base
- What
four main factors affect conductivity in lakes?
1.
2.
3.
4.
Experimental
Design
- Use the
"Data" section of the Web site to find the following information. Select
"Ice Lake" and "Current Profiles." Select the data for the week of Jan.
3, for the 2:00 p.m. sampling period. What changes occur in RUSS parameters
as the probe drops from the surface to the depths of the lake? Circle
the correct answer for your January profile.
With increasing
depth, temperature increases decreases stays the same
With increasing
depth, pH increases decreases stays the same
With increasing
depth, conductivity increases decreases stays the same
With increasing depth, dissolved oxygen increases decreases stays the same
With increasing depth, DO % saturation increases decreases stays the same
With increasing depth, turbidity increases decreases stays the same
- Now select the data for Ice Lake for the week of July 12, 1998. What changes occur
in this profile as the RUSS probe drops in the lake?
With increasing
depth, temperature increases decreases stays the same
With increasing
depth, pH increases decreases stays the same
With increasing
depth, conductivity increases decreases stays the same
With increasing
depth, dissolved oxygen increases decreases stays the same
With increasing
depth, DO % saturation increases decreases stays the same
With increasing
depth, turbidity increases decreases stays the same
- Compare
the water quality parameters for July to those in January. In what ways
are they similar or different?
- Using the method described in the WOW lesson on the heat budgets
of lakes (http://wow.nrri.umn.edu/wow/student/heat/study.html),
find the volume of Ice Lake.
V= _______________________
- In
early July1998, a strange pattern in conductivity measurements was recorded
in Ice Lake. Download the data and then graph conductivity at 1 m, 5
m, and 10 m depths in the lake for each of the dates indicated in the
table below.
Date
|
1
m Depth
|
5
m Depth
|
10
m Depth
|
6/28/98
|
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|
6/29/98
|
|
|
|
6/30/98
|
|
|
|
7/1/98
|
|
|
|
7/2/98
|
|
|
|
7/3/98
|
|
|
|
7/4/98
|
|
|
|
7/5/98
|
|
|
|
7/6/98
|
|
|
|
7/7/98
|
|
|
|
7/8/98
|
|
|
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7/9/98
|
|
|
|
7/10/98
|
|
|
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7/11/98
|
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7/12/98
|
|
|
|
Data
Management and Analysis
- Graph
conductivity vs. depth, creating a separate line for each day and use
the color plotter feature online to observe changes in conductivity
during the two week period. On what day did the conductivity values
peak? ___________________
- Were
there major changes in other water quality parameters during the two
week period beginning June 28, 1998? If so, what might these changes
tell you about the possibility of sensor error or data transmission
problems?
- Determine
the actual increase in conductivity for each of the following depths
for the two week period beginning June 28.
at 1 m =
__________ at 5 m = __________ at 10 m = _________
- What
is the average increase in conductivity during the two week period beginning
June 28, 1998? (Average the three values in #9.)
Interpretation
of Results
- What
factors might explain why the conductivity increases with depth in summer
and not in winter?
- List
some factors that might explain the jump in conductivity during the
two-week period beginning June 28, 1998.
- What
further lab or field research might help explain the increase in conductivity?
What other data could you download from WOW or other sources to help
identify the source of this conductivity increase?
- An
increase in conductivity of 100 uS is equivalent to an increase in salt
(sodium chloride) concentration of 0.05 g/liter. Using that correlation
and the volume of the lake, determine how much salt would be required
to produce the observed increase in conductivity. (Choose an appropriate
unit for the mass of salt.)
- Develop
a hypothesis for why conductivity increased in early July of 1998. Explain
and back up your theory with logical reasoning and evidence if possible.
Reporting
Results
- What
are some of the strengths and limitations of your teams theory
on the cause of the conductivity increase during early July 1998 in
Ice Lake?
|