Microthermal variability in a Welsh upland stream

This chapter yields insight into the spatial distribution of water temperature within a small upland stream and examines the potential impact of channel morphology, groundwater influence and hydrological flow conditions on microthermal patterns. Stream temperature was measured in situ at multiple sites over a 10-week summer period to reveal uniform thermal patterns with differences in mean daily water temperature across monitoring locations of less than 0.1 °C. Hence, channel water temperature within the study reach appears largely insensitive to morphological channel features such as channel incision, channel width-depth ratio and riparian vegetation. Thermal infrared (IR) imaging provided a useful tool to monitor temperature distribution within the channel in a spatially continuous way even though shading from the river bank and reflectance of solar radiation from the water surface may hamper the detection of temperature variation.