What is Instream Temperature Monitoring?

The Instream Temperature Monitoring program collects water temperatures from watershed streams during the summer months.

Why do we monitor instream temperatures?

Fish species, such as brook trout, brown trout and rainbow trout, are important indicators of stream health and support a vibrant recreational fishery within the watershed and Nottawasaga Bay. Trout and some aquatic insects require relatively cool, well-oxygenated water throughout the summer months to survive.

Instream temperature monitoring allows us to understand the distribution of trout species within the watershed and assists in our interpretation of stream health. It also shows us where trout populations may be stressed due to high summer temperatures and where stewardship projects such as dam removal and streamside tree planting may have the most benefit. Over the long term, instream temperature monitoring can be used to assess stream/ecological responses to weather trends and possible climate change.

How do we sample instream temperature?

Staff deploy dataloggers each summer to collect a continuous record of instream temperature at sites over a two week period. Staff and volunteers also collect instream temperature data using thermometers during dry, warm weather periods. These instream temperatures can be compared to maximum daily air temperatures to determine whether stream sections are cold, cool or warm.

Where do we monitor benthic invertebrates?

Approximately 35 sites are sampled each year within the watershed. Two of our ten subwatersheds are monitored each year so that we cover our entire watershed every five years. We also assist our Land and Water Stewardship Services program to monitor the effectiveness of stewardship projects such as dam removal.

What results are we seeing?

• Cool and cold water habitats are strongly associated with groundwater discharge areas, particularly those along the Niagara Escarpment, Oak Ridges Moraine and Oro Moraine

• Naturally occurring warm water habitats are present along the middle and lower portions of the Nottawasaga River

• The historical extent of cool and cold water habitats in the watershed has been restricted by: loss of forest cover along streams, construction of ponds on streams, conversion of wetlands to agricultural lands