Conductivity measures how well water can conduct an electrical current. Streams tend to have a relatively constant range of conductivity. Significant changes in conductivity (due to an increase in salt content such as chloride, bicarbonate, sodium or calcium) could suggest that a discharge or some other source of pollution has entered the stream.
This Rivers and Us resource is in a downloadable PDF format. Use it as a guide to the scientific methodology for measuring pH. It also contains discussion questions.
Acknowledgement: NIWA
