Copies of the Excel tutorial would be helpful to have on hand if students get stuck.
Show students photographs of flood events (local photos are included with this lesson). Ask: what do you think happens to a stream during a storm event? If students have completed the lesson “Storms and streams,” they should have a good idea of the types of physical changes, but chemical changes are difficult to measure without constant monitoring during the event.
Students will use the data set “Storm Chemistry” and choose a variable to study. Use the worksheet to guide them through this process. All students should first create a graph of rainfall and flow over time, in order to see the relationship between these two factors. Students can then work on different variables and try to understand the changes on their own.
There is a version of the worksheet available with graphs embedded in case you do not have access to Excel (or other graphing software) or prefer not to have the students graph the data.
Students may need help remembering how to use Excel. They also may be dissatisfied with data points that don’t point to an obvious pattern.
This data comes from a study that was done to try to understand what happens to different stream characteristics during a storm event. For a long time, scientists were not estimating the loads in stormwater when calculating watershed exports, and therefore had no idea how much nitrate or chloride ‘moves out’ during a big storm. Although students will not be doing these types of calculations, they should get an idea of the recovery that occurs in aquatic ecosystems and how long it takes for this to occur. For an extension of this idea, see the lesson titled “Ecosystem Disturbance: Deforestation” in the “Ecosystems in Action: Cycling of Matter & Energy” unit.
Students share their graphs and discuss whether or not their data supports their hypotheses. Ask students: How might exporting a large amount of nutrients in a short time period affect the local ecosystem? Have students discuss their thoughts in groups before presenting their ideas to the class. Evaluate: Assess student understanding by their answers on the associated worksheet.