Cooperative Fish and Wildlife Research Units Program: Arizona
Education, Research and Technical Assistance for Managing Our Natural Resources

We evaluated a ground-based hand-held thermal imaging system for measuring water temperatures using data from eight southwestern USA streams and rivers. We found hand-held thermal imagers could provide considerably more spatial information on water temperature (for our unit one image = 19,600 individual temperature measurements) than traditional methods could supply without a prohibitive amount of effort. Furthermore, they could provide measurements of stream surface temperature almost instantaneously compared to most traditional means such as hand-held thermometers (> 20 seconds per reading). Spatial temperature analysis is important for measurement of subtle temperature differences across waterways, and identification of warm and cold groundwater inputs. Hand-held thermal imaging is less expensive and equipment intensive than airborne thermal imaging methods, and is useful under riparian canopies. Disadvantages of hand-held thermal imagers include their current higher expense compared to thermometers, their susceptibility to interference when used incorrectly, and their slightly lower accuracy than traditional temperature measurement methods. Thermal imagers can only measure surface temperature, but this usually corresponds to subsurface temperatures in well-mixed streams and rivers. Using thermal imaging in select applications, such as where spatial investigations of water temperature are needed, or in conjunction with stationary temperature data loggers or hand-held electronic or liquid-in-glass thermometers to characterize stream temperatures by both time and space, could provide valuable information on stream temperature dynamics. These tools will become increasingly important to fisheries biologists as costs continue to decline. This work was published in the December, 2015 issue of the North American Journal of Fisheries Management.