Temperature Monitoring

Thermal (heat) pollution is often overlooked as a source of environmental impact to our streams. Thermal loading is the cumulative effect of increased water temperatures on aquatic organisms. Stream temperatures often increase when trees along streams are removed to make way for urbanization, agriculture, or grazing. The loss of shade allows more direct sunlight to reach the water and has the potential to warm runoff entering the stream through urban “heat island” effects. Thermal loading affects can be lethal if temperatures exceed upper tolerance limits of aquatic animals, and at the very least can cause stress which affects their development and behavior. 

In the State of Illinois, 89 stream miles were listed as “impaired” in 2018 due to thermal pollution (warmer than 16°C between December and March or warmer than 32°C between April and November). While this is a fairly low number of stream miles, water temperatures are rarely measured in smaller headwater streams at the frequency that would be required to catch these high temperatures.

RiverWatch now has water temperature data loggers available for committed volunteers to deploy at their stream site in the spring or summer and then retrieve in the fall. While deployed, the temperature logger will record water temperature hourly, giving RiverWatch high resolution data on changing stream temperatures.  If you are interested in learning more about the RiverWatch temperature monitoring program, please reach out to RiverWatch staff at riverwatch@lc.edu.