Thermal Imaging Camera Use: Identifying Groundwater Inputs to a Reef in American Samoa

Science Center Objects

USGS scientists used a thermal camera in American Samoa to understand the effect of land-based contaminants on an adjacent coral reef lagoon ecosystem. The infrared (IR) camera was used to capture thermal images of the lagoon to look for temperature differences to understand the distribution of freshwater entering the lagoon and the circulation of the lagoon water at various tidal levels.

As part of a larger study conducted by the USGS Utah and Arizona Water Science Centers in American Samoa, USGS hydrologists used a thermal infrared (IR) camera 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.

 

Benefits of Thermal Imaging Camera

Use of the handheld thermal imaging camera provided several benefits, including:

  • improved understanding of the extent of freshwater input to a coral reef lagoon, and
  • rapidly produced easy-to-understand images that were used to inform selection of locations for deployment of other water-quality sensors.
USGS scientist collects thermal images on hill of shoreline in American Samoa

USGS scientist collects thermal images of shoreline in American Samoa. (Credit: USGS Utah Science Center and USGS Arizona Water Science Center)

 

Thermal image indicates water temperature,  warmer temperatures are represented as red and cooler temperatures as blue.

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.) (Credit: USGS Utah Science Center and USGS Arizona Water Science Center)

 

USGS scientist collects thermal images with camera next to a lagoon in US Samoa

USGS scientist collects thermal images of lagoon in American Samoa. (Credit: USGS Utah Science Center and USGS Arizona Water Science Center)

 

 Thermal image indicates water temperature, where warmer temperatures are represented as red and cooler temperatures as blue.

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. (Credit: USGS Utah Science Center and USGS Arizona Water Science Center)