Stream Monitoring

At the request of Emily Heald (UW-Madison Division of Extension | Natural Resources Institute Rivers Educator), Rick Eilertson, volunteer with the Friends of the Baraboo River, installed thermistor devices in 3 streams that drain into the Baraboo River within Sauk and Columbia Counties (Boulder Creek, Rowley Creek, and Leech Creek) in early May 2026 to gather continuous stream temperature throughout the spring, summer, and fall months. Rick and/or other volunteers will be checking the thermistors monthly before pulling them out in late October/early November and delivering to the DNR for compiling the temperature data into DNR's stream monitoring database. This data will be correlated with the fish surveys that DNR plans to do in these 3 streams during Summer 2026.

Why This Matters

Continuous stream temperature monitoring using thermistors provides a practical and reliable way to collect real-time data about changing water conditions. A thermistor is a temperature-sensitive resistor that changes electrical resistance as temperature changes. When placed in or near a flowing stream, the thermistor can record frequent temperature readings, allowing researchers, educators, or environmental monitors to observe daily and seasonal temperature patterns. This type of continuous monitoring is more useful than occasional manual readings because it captures temperature fluctuations that may occur throughout the day or during weather events.

Stream temperature is an important indicator of aquatic ecosystem health. Many fish, insects, amphibians, and microorganisms depend on specific temperature ranges for survival, reproduction, and growth. Sudden increases in stream temperature can reduce dissolved oxygen levels and place stress on aquatic organisms. Continuous thermistor data can help identify patterns related to shade loss, runoff, groundwater input, drought, stormwater discharge, or seasonal warming. By tracking these changes over time, stakeholders can better understand whether a stream environment is remaining stable or experiencing thermal stress.

Thermistors are especially useful because they are small, relatively affordable, and capable of recording data at regular intervals over extended periods. When paired with a data logger, a thermistor can collect temperature measurements every few minutes or hours without constant human supervision. The resulting data can be graphed to show trends, compare locations along a stream, and support decisions about conservation, restoration, or land-use planning. For students and community groups, continuous stream temperature monitoring also provides a meaningful hands-on way to connect science, technology, and environmental stewardship.