How can we determine if water is safe for human consumption or recreation? How is the biological community affected by pH, nitrogen and phosphorus influxes, dissolved oxygen levels, and turbidity? Objective Students will: - Understand how water chemistry data can help quantify the health of a stream. - Make predictions about the cause and effect of certain water chemistry conditions. Preparation Instructor should review the presentation and accompanying handout before instruction. Total preparation time: about 20 minutes. Materials Microsoft PowerPoint presentation Download Indicators of Water Duration: 30 Minutes.