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Using Fiber-Optic Distributed Temperature Sensors to Monitor Ground-Water and Surface-Water Processes and Interaction

J.W. Lane, Jr.

Abstract

A new fiber-optic distributed temperature sensor (FO-DTS) based on laser backscatter technology allows for high-resolution, real-time monitoring of temperature along the entire length of an optical fiber. Commercially available FO-DTS technology can achieve spatial resolution of less than 1 meter and thermal resolution of less than 0.1 degree Celsius, at sub-minute measurement intervals. Measurements are taken along one or more standard or reinforced telecommunications fiber-optic cables, which serve as distributed thermal sensors with hundreds to thousands of data points acquired over lengths up to tens of kilometers.

In the spring of 2006, the U.S. Geological Survey, Office of Ground Water, Branch of Geophysics began a six-month FO-DTS technology demonstration/evaluation project. Results are presented from several FO-DTS pilot studies, at the 100-meter to kilometer scales. Study goals include mapping submarine ground-water discharge, identification of gaining stream reaches, and inference of transmissive fractures in boreholes. For each project, additional hydrologic, chemical, or geophysical data are used to help confirm interpretations based on the fiber-optic temperature monitoring results.

Final copy as submitted to National Ground Water Association Ground Water Summit for publication as: Lane, J.W., Jr., 2007, Using fiber-optic distributed temperature sensors to monitor ground-water and surface-water processes and interaction [abs.]: NGWA Ground Water Summit, Albuquerque, New Mexico, April 29 - May 30, 2007, Proceedings: Westerville, Ohio, National Ground Water Association.