A practitioner's guide to thermal infrared remote sensing of rivers and streams: recent advances, precautions and considerations

Abstract

Stream temperature is a key habitat variable controlling all physical and biological river processes. In light of the threat of climate change to fluvial environments, growing importance is being placed on the need to gain a better understanding of stream temperature dynamics. However, many current or historic stream temperature datasets are of very low spatial resolution. Such in situ measurements are often unable to provide the fine scale information on longitudinal or lateral temperature patterns necessary for understanding links between thermal heterogeneity and fluvial processes. In recent years, attention has therefore turned to the use of thermal infrared (TIR) remote sensing in order to acquire 2D stream temperature data at ecologically meaningful scales. While TIR remote sensing is a relatively mature technology in its own right, its application in fluvial environments is accompanied by a range of limitations and considerations that must be respected in order to ensure the acquisition of reasonable quality data. It is only in recent years that researchers have been started to shift from detailing the technical aspects of TIR imaging of river environments toward describing its application for river management and fundamental fluvial science. We critically review this recent research, demonstrating the utility of TIR for applied river temperature research. We also provide a detailed guide to the practical use of TIR in river environments with a view to further stimulating its use for advancing stream temperature science.

Big biology meets microclimatology: defining thermal niches of ectotherms at landscape scales for conservation planning

“…introDuction Interest in thermal ecology is growing given concerns about global environmental change, the importance of temperature to many biological processes (Angilletta 2009, Kingsolver 2009, Cooke et al 2013, and the ease with which temperature data are collected (Angilletta and Krochmal 2003, Selker et al 2006, Dugdale 2016. Thermal environments are particularly relevant for ectotherms because of their limited ability to physiologically regulate metabolic processes, so these organisms develop behavioral patterns and life histories that adjust to thermal resources over daily, seasonal, and annual cycles (Sunday et al 2014, Woods et al 2015.…”

Exploring Streamwater Mixing Dynamics via Handheld Thermal Infrared Imagery

“…During storm events, surface roughness, deeper water columns as well as stream temperature homogenisation due to precipitation tend to influence the applicability of remotely sensed data [27,45]. Consequently, because we are making these measurements for the first time we concentrated on winter low flows, when these disturbances were small and temperature contrasts more pronounced.…”

“…The images were taken by positioning the handheld camera perpendicular to the stream section under study and trying to cover the widest possible width with a single image. Since our purpose was to extract temperature cross-sectional distributions from the thermal images, we avoided using the panoramic picture mode, where shifts in absolute temperature can occur between contiguous images as a product of the camera's non-uniformity correction [27]. Moreover, both confluences were chosen in cleared areas in order to avoid tree shading effects which can influence the temperature detection.…”

“…Among these measurement tools, TIR cameras are particularly suitable for the collection of temperature data at multiple spatial and temporal scales with high resolution [26,27], overcoming the limitations of discrete measurements. To date, airborne and ground-based TIR imagery have been successfully used to describe longitudinal profiles of river temperature [27][28][29][30], to provide information on soil moisture and surface saturation patterns [31,32], to detect ground water exfiltration along the hillslope-riparian-stream continuum and inferring connectivity dynamics of water exfiltrating to the stream [33][34][35][36][37].…”

“…To date, airborne and ground-based TIR imagery have been successfully used to describe longitudinal profiles of river temperature [27][28][29][30], to provide information on soil moisture and surface saturation patterns [31,32], to detect ground water exfiltration along the hillslope-riparian-stream continuum and inferring connectivity dynamics of water exfiltrating to the stream [33][34][35][36][37]. Furthermore, information obtained through TIR imagery has been used as a data source for hydrological model validation [32,38].…”