Hydrofracking Data - Turbidity

Advance preparation: Prepare a bag for each pair (or group) of students that has two different colors of dried beans (any two colors will work).  You want to have enough beans in the bag so that students need to take the beans out of the bags and carefully count them.  We suggest bags of 40-50 beans per color.  Each bag needs to have the same amount of beans- but don’t tell the students this!   You will limit the amount of time it takes them to count the beans, and providing a distraction while they are counting can also be helpful.  We suggest giving students 1 minute to count if you use 50 beans per color.  This reminds students how easy it is to make mistakes when you aren’t paying close attention!  For a fun introduction to this idea, consider watching the “Gorilla in the Room” video: http://www.youtube.com/watch?v=m_8nJZ_VUKY .  This video shows two teams of students (team white vs team black) passing basketballs.  Students are asked to count how many times the white team passes their ball.  Most students will completely miss the gorilla that walks into the middle of the basketball court during the 1-minute exercise. 

1. Engage:  Students may not be familiar with turbidity.  There is an online video that may help you: http://www.youtube.com/watch?v=MFpCJsc_k64 , which shows erosion.  Other options are a video about sampling turbidity or having the students do a reading.  An easier route, though, would be to take some sediment (soil, detritus), place it in a jar with water, and shake it vigorously.  If you have a turbidimeter available, measure the turbidity in the shaken jar.  Then, allow it to settle and measure it again. 

2. Explore: Hand out the student worksheet, “Hydrofracking Data” and ask students to answer the first two questions about turbidity.  Then, have the students create the prediction graph and share their ideas.  Students may have a range of ways they think turbidity and the number of fracking wells are related - probe their answers to see if they have a reason for why turbidity might change with the increase in wells.  Next, have them graph the turbidity data in the space provided.  This turbidity study was conducted in a watershed in Arkansas where new fracking wells are being developed in the Fayatteville shale; the researchers sampled seven streams that had different densities of gas wells in their drainage area.  Turbidity was measured with a Hach meter during the spring flow; overall, the students should notice a relationship between the number of wells and turbidity.  As the number of wells in an area increases, turbidity increases.  Prompt students to explain why this might be happening - the idea is that more wells means more construction in an area, thus more disturbance of the soil.  Once students have produced the graph, begin a discussion of variability.   They should notice that there is not a direct relationship.  
3. To introduce the concept of variability, give each pair (or group) of students a bag of beans.  Give students a defined amount of time (less time if you have fewer beans – I recommend limiting the counting to 1 minute if you have 50 beans per bag) and ask them to count all of the beans in the bags.  Tell them that both speed AND accuracy matter.  Once students have counted, they should come up to the board and write down their counts on the board.  Don’t allow students to recount their beans.
4. Compare and discuss the students’ results – are they the same?  Do some counts differ?  Why?  What are some reasons for the differences – could it be due to human error, or actual differences between the bags?
5. Next, provide students with the natural objects – leaves, pine needles, etc.  They should have enough of the objects so that when they compare them, they are similar but not exactly the same.  Ask students to measure the diameter of the leaves or the lengths of the pine needles, and record the results.  Students should share their results.  Ask:  Why are there differences between the leaves?  Are these differences due to the leaves, or to human error?  Brainstorm answers to both questions. 
6. Explain: Place this chart up on the board, and fill in with student help (students have a copy of this chart in their packet).  Ask students to think about potential error with reference to the turbidity data.   Some examples are included below.

 Students often focus on human error instead of thinking about the types of changes that might naturally occur in the ecosystem.  Make sure they can also recognize some natural variability in the system.  Finally, show students the “Beans Example Template” that gives an example of the bean data – this spreadsheet will show you an example of the activity.  (You can also put in your own bean count data.)  First, you can see the bean counts individually (as a scatter plot), the averaged bean counts (bar graph), and a bar graph with error bars.  Ask students to explain the benefits and drawbacks of the different types of graphs.  Students should recognize that error bars allows them to have some information about the range of the data in the sample, similar to a scatter plot, but with the additional benefit of knowing the average of the set of data.  This idea will be reviewed in the last lesson.

7. Scientists are concerned that if proper safeguards are not put into place, and the number of wells continues to increase, it could have a significant impact on streams.  Construction of any sort can lead to increased turbidity due to erosion.  Scientists are concerned that if proper safeguards are not put into place, and the amount of wells continues to increase, it could have a significant impact on streams.  This schematic, taken from a paper by Entrekin et al (2011), shows how total dissolved solids could increase both from the supporting infrastructure of fracking and the treatment and waste handling of the flowback water. 
8. Extend: Students could research the ecological impacts of removing water from stream systems (reducing base flow). 

9. Evaluate: Students should complete the worksheet.  Pay attention to whether students are able to explain their claim about whether a change in turbidity will affect the aquatic ecosystem.