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Fiber-Optic Distributed Temperature Sensing in Waquoit Bay, Massachusetts

Overview

In 2006 the USGS Office of Ground Water, 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 ground-water 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 Ground-Water 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 ground-water 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 ground-water 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

Photo Gallery

Figure 1. The Waquoit Bay National Estuarine Research Reserve is located in Massachusetts.	Figure 2. The study area is located just off shore in Waquoit Bay, Massachusetts.
Figure 3. Charles Harvey (MIT) and Fred Day-Lewis (USGS) prepare the fiber-optic distributed temperature sensing system. To relieve strain on the cable, it was taped to a heavy rope.	Figure 4. Hannan Karam (MIT) connects the distributed temperature sensor to a laptop computer. This allows temperature data to be monitored real-time and (or) saved and analyzed later.
Figure 5. Hanan Karam (MIT) attaches floats to the cable and rope to help with the deployment.	Figure 6. Fred Day-Lewis (USGS) deploys the cable off shore.
Figure 7. Seepage meters being prepared for installation by MIT graduate students.	Figure 8. Seepage meters and salinity measurements at pipes along the cable provided ground truth.

For More Information

For more information about the Waquoit Bay FO-DTS project, contact Fred Day-Lewis (daylewis@usgs.gov or 860-487-7402 x21) at the OGW, Branch of Geophysics.

This project was conducted with support from the USGS Ground-Water Resources Program.

Collaborators & Cooperators

• Dr. Charles Harvey, MIT Civil and Environmental Engineering Hydrogeology Group
• Waquoit Bay National Estuarine Research Reserve

References

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://video.wr.usgs.gov/wrd/30Nov2006.wmv).