USGS Groundwater Information: Branch of Geophysics
Handheld Thermal Imaging Cameras > Example: Identifying Groundwater Inputs to a Reef
USGS hydrologists recently used a thermal camera in American Samoa as part of a larger study designed to understand the effect of land-based contaminants on an adjacent coral reef lagoon ecosystem. In order to understand the fate of the contaminants, scientists need to understand the distribution of freshwater entering the lagoon and the circulation of the lagoon water at various tidal levels.
The infrared (IR) camera was used to capture thermal images of the lagoon from the top of a nearby mountain to look for temperature differences between fresh water (cooler) and ocean water (warmer) which may indicate fresh-water input. Images were taken during various tidal levels and times of day, including through the night. As part of the larger project, strings of temperature sensors were deployed and water-quality profiles were also collected across the lagoon to identify salinity and thermal differences.
Thermal images captured the temperature contrast where fresh water flows to the ocean through a deep cut in the reef (ava). In addition, the camera was used to identify a previously undetected thermal anomaly for further study. The information gained from use of the thermal camera informed scientists' understanding of the circulation of surface water in the reef. However, because the camera only measures surface temperatures, it was difficult to identify small scale fresh-water inputs that did not result in differences in surface temperature observable with the camera.
Figure 1. USGS scientist collects thermal images of shoreline in American Samoa. Image courtesy USGS Utah Science Center/USGS Arizona Water Science Center.
Figure 2. Thermal image indicates water temperature, where warmer temperatures are represented as red and cooler temperatures as blue. The image presents an area where groundwater may be discharging into the lagoon. Temperature is in degrees Celsius. (The linear red feature extending from the left edge to the center of the image is a road.) Image courtesy USGS Utah Science Center/USGS Arizona Water Science Center.
Figure 3. USGS scientist collects thermal images of lagoon in American Samoa. Image courtesy USGS Utah Science Center/USGS Arizona Water Science Center.
Figure 4. Thermal image indicates water temperature, where warmer temperatures are represented as red and cooler temperatures as blue. The image presents an area where warmer groundwater (red) may be discharging into a lagoon. Temperature is in degrees Celsius. Image courtesy USGS Utah Science Center/USGS Arizona Water Science Center.
Use of the handheld thermal imaging camera by the USGS Utah and Arizona Water Science Centers for this project
For more information about the use of the thermal imaging camera in this project please contact USGS hydrologist Kim Beisner (firstname.lastname@example.org) at the USGS Arizona Water Science Center. For more information about the project in general, please contact USGS research ecologist Anne Brasher (email@example.com) at the USGS Utah Water Science Center.
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