PERSISTENCE AND HETEROGENEITY: EXPLORING STREAM TEMPERATURE VARIABILITY AS OBSERVED BY UAV-COLLECTED TIR IMAGERY

Stream temperature is an important metric for determining the health of a stream system, both in terms of nutrient cycling, available oxygen, and aquatic habitat. Most stream temperature analyses have been conducted using an array of sensors creating a discrete picture of stream temperature through time via in situ observations. However, thermal infrared (TIR) imagery collected via unmanned aerial vehicles (UAV) offers potential to augment these measurements by characterizing the heterogeneity of stream temperature in space. For this study, we used thermal infrared (TIR) imagery collected via unmanned aerial vehicle (UAV) to document the heterogeneity of stream temperature across the stream channel and down the length of a stream. Our study site focused on a 2.4 km stretch of a local river (Onondaga Creek) in Syracuse, NY. The TIR images effectively create a continuous, two-dimensional sampling of stream temperature along the study area. We analyzed images collected from four flights spaced monthly from April 2017 through July 2017. The images reveal that stream temperature is heterogeneous both across and downstream. In fact, heterogeneities derived from artificially channelized inputs to the stream were documented to persist as far as 290m downstream from their source, depending on the time of year. Overall, this study reveals that stream temperature heterogeneity is variable throughout the year and ultimately determined by the interaction between in-stream temperatures and artificially channelized sources.