Now that you have collected data, it's time make sense of it. Compare your data to the scientific standards for clean water. Make a claim about whether the water is healthy or polluted, using your data as evidence and the standards for clean water as the basis for your REASONing.


data tree

Based on an analysis of the data you collected in the GATHER stage, does your initial explanation of the phenomenon "hold water" when applied to the creek or stream you tested? Have you learned anything that could help you revise or refine your explanation to be more accurate and complete? For instance:

  • If you conducted physical and chemical tests, use this Water Quality Index Calculator to compare your results to the standards for each parameter and overall.
  • If you sampled aquatic macroinvertebrates, use this Biotic Index Calculator to compare your results to the standards for each category of macroinvertebrates.
  • If you conducted a streamside habitat survey, use this Score Calculator to compare your results to the scores of other streams.
  • If you gathered other data, display it in a graph to make it easier to spot patterns or trends and analyze their significance. Try this online graph-maker: Create A Graph. Think about how you could compare your data to a standard. What would be your authoritative source? What conclusions about water quality can you draw from your data and findings?


Convert your explanation to a claim about the water quality of the stream you tested. Note this C-E-R form and scoring rubric you can use to make your argument.

  • Make a Claim that answers the question: What is the water quality of the creek we tested?
  • Support the claim with Evidence (test results and other data you gathered).
  • Connect the evidence to the claim with scientific Reasoning by comparing your data to the ideal level (the standard) for each parameter such as phosphates, nitrates, dissolved oxygen, pH and turbidity; or sensitive vs tolerant macroinvertebrates; etc. Explain the significance of your findings, according to a a scientific principle or an authoritative source.
  • Revise the claim to be consistent with the evidence, if necessary.


problem tree

Based on your claim, evidence (data), and reasoning, what problems are affecting the stream's water quality? (Hint: Were there there any parameters for which the data was not in an acceptable range? If all the test results were ideal, are there any pollutants for which you did not test? How could you find out more about those parameters?)

Select one of your stream's water quality problems and focus on its causes, its consequences or effects, and and their significance. Identify and write about this problem in the Reason section of your Portfolio. Identify factors that cause or contribute to the problem.  Consider what happens as a result of this problem. Why does it matter?

Deliverable: Problem Statement

Identify a problem with the water quality of the stream or pond you investigated.

Break the problem down into bite-sized tasks and decide on one that you will try to solve.

I analyzed my data about the stream or pond we are investigating.
I made a claim about the quality of water, backed by evidence (my data) and reasoning.
I used my data analysis to create a problem tree in my portfolio.
I identified a component of the problem that I will try to solve.