Temperature affects many of the chemical and physical properties in streams. Macroinvertebrates will not survive in temperatures above 22°C, and higher temperatures also increase conductivity.
This Rivers and Us resource is in a downloadable PDF format. Use it as a guide to the scientific methodology for measuring water temperature. It also contains discussion and reflection questions.
New Zealand’s freshwater aquatic animals prefer colder temperatures. Their natural habitat is in well-shaded waterways through forests. Without dense forest cover, streams across New Zealand are exposed to more sunlight and higher temperatures.
Aquatic macroinvertebrates struggle to survive in water warmer than 22°C, and few invertebrates can live in temperatures above 30°C.
The chemistry of the water changes as it warms. Warmer water holds less oxygen than colder water, increases the sensitivity of aquatic animals to toxins and disease and speeds up chemical reactions and biological processes.
Temperature will fluctuate over a 24-hour period so it is important to record the time and the weather conditions when you take the temperature reading.
Measure temperature in the main flow of the stream. Leave the thermometer in the water for at least a minute or until the reading stabilises.
And don’t forget to always use the same testing protocol to ensure robust data that can be used to compare over time.
The Fairfield Project
Hannah and Jess, Waikato Diocesan School for Girls
Stream footage: Dairy NZ, Healthy Farms Healthy Rivers and Waikato Regional Council
Invertebrate guide, Greater Wellington Regional Council
This video has been developed in partnership with the Waikato Regional Council as part of the Rivers and Us resource.