USGS Groundwater Information: Branch of Geophysics
New geophysical methods are required for monitoring hydrologic processes at the catchment and larger scales, and for quantifying fluxes between groundwater and surface water. Fiber-optic distributed temperature sensing (FO-DTS) is an emerging technology that has promise for characterizing estuary-aquifer and stream-aquifer interaction and for identifying transmissive fractures in bedrock boreholes. Although routinely used for monitoring temperature and (or) strain in petroleum wells, FO-DTS applications in hydrology are uncommon.
In the spring of 2006, with support from the USGS Groundwater Resources Program, the USGS Office of Groundwater, Branch of Geophysics began a six-month FO-DTS technology demonstration/evaluation project. As part of this project, several FO-DTS pilot studies were conducted at the 100-meter to kilometer scales. Study goals included evaluating the use of FO-DTS for:
For each project, additional hydrologic, chemical, or geophysical data were used to help confirm interpretations based on the fiber-optic temperature monitoring results.
FO-DTS measurements involve sending laser light along a fiber-optic cable. Photons interact with the molecular structure of the fibers, and the incident light scatters. Analysis of Raman backscatter for variation in optical power allows the user to estimate temperature. Analysis of Brillouin backscatter for variation in optical frequency allows the user to estimate temperature and strain.
Commercially available FO-DTS technology can achieve:
Spatial, thermal, and temporal resolution are mutually dependent, and depend on measurement configuration.
The Branch of Geophysics has sponsored fiber-optic distributed temperature sensor technology demonstration and evaluation projects by USGS researchers in estuarine and riverine locations around the Nation:
For more information about applied research on the use of FO-DTS, contact John W. Lane, Jr., Chief, Branch of Geophysics (firstname.lastname@example.org or 860-487-7402 x13) or see the publications listed below.
This project was conducted with support from the USGS Groundwater Resources Program.
Learn about scheduled OGW Branch of Geophysics courses and workshops on FO-DTS.
Day-Lewis, F.D., Karam, H.N., Harvey, C.F., and Lane, J.W., Jr., 2006, Monitoring submarine groundwater discharge using a distributed temperature sensor, Waquoit Bay, Massachusetts [abs.]: EOS Transactions, American Geophysical Union, v. 87, no. 52, Fall Meeting Supplement, Abstract NS24A-02, Invited.
Day-Lewis, FD and Lane, J.W., Jr., 2006, Using a Fiber-Optic Distributed Temperature Sensor to Understand Ground-Water/Surface-Water Interaction: U.S. Geological Survey Water Resources Discipline - Wester Region Research Seminar Series, November 30, 2006 (video online at mms://video.wr.usgs.gov/wrd/30Nov2006.wmv).
Day-Lewis, FD, and Lane, J.W., Jr., 2006, Watershed-scale temperature monitoring of hydrologic processes [abs.]: Hydrogeophysics Workshop, Vancouver, British Columbia, July 31-August 2, 2006, Proceedings, Society of Exploration Geophysics.
Lane, J.W., Jr., 2007, Using fiber-optic distributed temperature sensors to monitor groundwater and surface-water processes and interaction [abs.], in NGWA Ground Water Summit, Albuquerque, New Mexico, April 29- May 30, 2007, Proceedings: Westerville, Ohio, National Ground Water Association.