Dam operations restrict or eliminate connectivity longitudinally, laterally, vertically, and temporally and can affect thermal heterogeneity, particularly mixing of the water column. We examined thermal heterogeneity across space and time in two tributary confluences before and after instream structures were constructed (i.e., large woody debris, gravel spits) in a dam-influenced river in the inland Pacific Northwest (USA) during summer months. Structures were placed to reduce mixing of cold water from tributaries with warm water from the mainstem and promote scouring to create pools for coldwater fishes. To describe thermal and hydrologic patterns, we used thermal infrared (TIR) imagery from an uncrewed aerial vehicle (UAV), high- resolution in-situ thermographs, and flow data from an upstream gage. Preliminary results revealed that cold water (<16 °C) was mostly maintained near the substratum within the confluence areas throughout July and August after structures were installed. Mainstem flows were more important than air temperature in influencing the magnitude of stratification and can dissipate the cold-water plumes rapidly once the plumes move past the gravel spits. However, flows below 140 m3s-1 in the mainstem reduced the amount of usable area for fish behind the gravel spits due to insufficient water depth, suggesting that minimum instream flows may be needed to maximize the effectiveness of instream structures designed to enhance cold-water refuges. Preliminary findings also suggest that using multiple tools can help identify the extent to which surface-release flows influence the persistence and size of cold-water refuges.