USGS Groundwater Information: Branch of Geophysics
Figure 2. Example of portable, handheld thermal imaging camera used in USGS groundwater studies.
Figure 1. Example of portable, handheld thermal imaging camera used in USGS groundwater studies.
USGS Science Centers are using high-resolution handheld thermal imaging cameras (figs. 1 and 2) in groundwater/surface-water interaction studies and other investigations where thermal signatures are of interest. The cameras can be used to image streams, lakes, and adjacent structures (e.g., banks, bars, seeps, etc.) to quickly locate and characterize thermal anomalies in real time at a scale of centimeters to tens of meters. Variations in temperature can be used to track (or trace) the heat carried by flowing water, such as during groundwater discharge into a stream.
Although airborne and satellite thermal imaging for water-resources studies is common, the availability of robust handheld thermal imaging tools in support of USGS groundwater studies is relatively new. The cameras' allow hydrologists to rapidly image real-time variations in temperature at high resolution in the field. The information can be used to
The small size of the cameras makes them convenient tools for studies in dense urban settings as well as remote field sites. Potential field applications are being explored within the USGS Water Mission Area and in interdisciplinary work with other USGS Mission Areas.
Temperature has long been recognized as an important water-quality parameter. Differences between temperatures in a stream and surrounding sediments can be analyzed to trace the movement of groundwater to and from streams and to better understand the magnitudes and mechanisms of stream/groundwater (hyporheic zone) exchanges. Figures 3 and 4 show how thermal imaging can be used to rapidly identify, visualize, and quantify differences in water temperature that may indicate groundwater discharging to the surface. To learn more about use of heat as a tracer, see "Heat as a tool for studying studying the movement of ground water near streams."
Figure 3. Thermal image displayed as an inset of the true-color photograph taken in the field. Thermal image indicates water temperature, where warmer temperatures are represented as red and cooler temperatures as blue. The image presents an area where cooler groundwater (blue) may be discharging along a warm stream bank in mid-summer. The photo spans an area about 3 meters across. The temperature scale is in degrees Celsius. USGS/Image by Martin Briggs.
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 cooler (blue) stream in late fall at Tidmarsh Farms, Massachusetts. (Learn more about the Tidmarsh Farms wetlands restoration and conservation project .) The image spans an area about 6 meters across. Temperature is in degrees Celsius. USGS/Image by Martin Briggs.
The USGS Branch of Geophysics has sponsored handheld thermal imaging camera technology demonstration and evaluation projects by USGS researchers in around the Nation. Examples of recent applications include:
Briggs, M.A., Voytek, E.B., Day-Lewis, F.D, Rosenberry, D.O., and Lane, J.W., 2013, The hydrodynamic controls on thermal refugia for endangered mussels in the Delaware River : Environmental Sciences and Technology: v. 47, no. 20, p. 11423-11431. doi:10.1021/es4018893.
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