Temperature directly and indirectly affects abiotic and biotic processes in rivers and streams, and can vary widely by different locations in the watershed and across seasons and flow regimes. Temperature can also vary across smaller spatial distances, shaped by factors like groundwater connectivity, channel morphology, and riparian shading. This lesson engages students in a structured, team-science activity to identify thermal heterogeneity in a river reach, and discuss the factors that influence spatial patterns in temperature and the implications of thermal heterogeneity. To prepare for the lesson, assigned readings before the field exercise may be useful if students are not already familiar with stream channel morphology and hydrology (see recommended reading). Students will also use remote-sensing imagery to familiarize themselves with the stream reach before the field visit. During the field portion of the lesson, students will individually sketch and annotate an illustration of the river reach, will work in small groups to generate hypotheses and determine sampling locations, and will collect temperature data using thermisters or handheld thermometers. Students will report findings back to the full class toward the end of the field session, and collaboratively build a map of the river reach depicting temperature and annotating hypothesized drivers. They will also consider questions related to the implications of water temperature and spatial and temporal thermal heterogeneity. This lesson will guide students through a full cycle of inquiry: observation, hypothesis generation, sampling design, data collection, collaborative synthesis, and ecological interpretation. Students will be evaluated on diagnostic, formative, and summative aspects of their work; this will include their initial observations and hypotheses, their collaborative map, and their answers to synthetic questions on the abiotic and biotic implications of temperature heterogeneity. Optionally, this lesson may also be modified to involve other learning outcomes such as use of spatial tools such as GIS or Survey123, or data analysis exercises using publicly-available water temperature time series. This lesson is also well suited to comparative studies (e.g. headwaters versus mainstem, or forested versus urban watersheds), and may be repeated in subsequent field trips or at different locations on a multi-day river trip.
Rachel Hovel (Fri,) studied this question.