Fiber-Optic Distributed Temperature Sensing in Waquoit Bay, Massachusetts

Science Center Objects

In 2006 the USGS Office of Groundwater, Branch of Geophysics (OGW BG) conducted a technology demonstration and evaluation project in Waquoit Bay, East Falmouth, Massachusetts, to evaluate the use of fiber-optic distributed temperature sensing (FO-DTS). In this project, the USGS used FO-DTS to investigate aquifer-estuary interaction by monitoring submarine groundwater discharge in Waquoit Bay. OGW BG conducted the project at the Waquoit Bay National Estuarine Research Reserve in cooperation with scientists from the Massachusetts Institute of Technology(MIT) and with support from the USGS Groundwater Resources Program.

The results of the demonstration and evaluation project indicate that high spatial and temporal resolution of thermal variations is possible with FO-DTS. In addition, the FO-DTS results were consistent with direct measurements of submarine groundwater discharge.

During the project, multiple equipment systems were used, and a variety of data sets were collected in addition to FO-DTS, including direct temperature sensors at discrete points, seepage measurements, and pore-fluid salinity measurements. Previous research conducted by MIT scientists at the site also provided important background information.

The FO-DTS cable was deployed over an 80- by 60-meter area just offshore. As configured, the resolution along the cable was approximately:

  • Spatial resolution along cable: ~1 meter
  • Temporal resolution: ~1 minute
  • Thermal resolution: 0.1 degree Celsius

To identify submarine groundwater discharge into the Bay, data were analyzed for:

  • Near-shore cold region
  • Tidal influence that diminished with distance offshore
  • More stable temperatures beyond 30 or 40 meters offshore
  • Effects of water temperature, tides, and precipitation



Day-Lewis, F.D., Karam, H.N., Harvey, C.F., and Lane, J.W., Jr., 2006, Monitoring submarine ground-water 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://