Watershed Assessment
Analysis of Data
Q Values
• Raw data values are NOT Q values.
• We need to convert the raw data/observations into “grades” (Q
values)
• Post all of your group’s collected abiotic and biotic data on the board
such that averages may be obtained.
Temperature
1. Find difference between highest and lowest temperatures
for the pond (∆T). Consider ALL of the collected values for
each location (not just your class)
2. Use the Table 4 in your lab handout to determine the
“grade”/Q value for temperature
3. The smaller the difference, the higher the Q value
4. Repeat steps 1-3 for the river
Dissolved Oxygen
• To determine the Q value for D.O., we must first
determine how much oxygen the water source could
be expected to have at its temperature
• Calculate the average D.O. for the pond
• Use the nomogram on page 3 of your lab handout to
determine the % saturation for the pond. Use AVG
temp. and AVG D.O.
• Once you have determined % saturation for the pond,
use table 1 to determine the Q value for Dissolved
Oxygen
• If % saturation exceed 100%, you will have to
extrapolate the Q value on table 1
• Repeat steps 2-4 for the pond
pH and Total Dissolved Solids
1. Use the appropriate tables (2-3) to determine the Q value for each
parameter
2. Average the pH readings for the pond and use the appropriate table to find
the Q value
3. Average the TDS readings for the pond and use the appropriate table to
find the Q value
Note: NTU = mg/L
4. Extrapolate if the average pH or TDS is between the increments on your
table
5. Repeat steps 1-3 for the river
6. While low TDS/turbidity values are desired, moderate pH values are desired
Benthic Macroinvertebrates
• Benthic Macroinvertebrate Q value does NOT factor
into the overall abiotic Q value
• Unlike the abiotic Q values, a lower Q value for
benthic macroinvertebrates is indicative of a healthier
ecosystem
• High biodiversity of pollution tolerant species is
indicative of an unhealthy ecosystem
Fecal Coliform
• Obtain your Coliscan plate from the incubator and view under a
stereoscope
• Count all purple and pink fecal coliform colonies on your plate. Keep a
separate tally of purples alone as they represent E. coli
• Since you sampled 5mL of water, multiply your total # of f.c. x 20 to express
as total number of fecal coliform/100mL
• Post your findings on the board and average the number of fecal coliform
for the water source
• Using Chart 2 on p.7 of your lab, use the class average to calculate the Q
value for fecal coliform.
• Make sure you obtain the results for both river and pond
Conclusion
• To determine the relative health of each ecosystem (river and pond), think about its overall
abiotic Q value, its benthic macroinvertebrate Q value and its fecal coliform. The last two factors
should be about 1/3rd of your consideration.
• Cite specific data AND Q values when supporting your decisions about the health of each
ecosystem
• For each parameter (pH, temp, etc.) you should attempt to explain why it was healthy or
unhealthy using logical reasoning. This needs to be addressed for both river and pond.
• You are comparing the systems but also addressing each’s individual health
• Include any qualitative observations in your decisions
• Be sure to address both confounding variables AND sources of error
Data Presentation
• Data tables (2): one for abiotic Q values, one for biotic Q values
• Graph the Q values for 5 of the 6 values (do not graph benthic
macroinvertebrates Q value as it is inverse)
• Bar graph format