T41 Innovations and New Technologies for Measuring and Characterizing Groundwater–Surface Water Interaction

Sunday, 28 October 2007
1:30 PM - 5:30 PM

DISTRIBUTED TEMPERATURE SENSING: DESIGN AND PROTOCOLS FOR HYDROLOGIC APPLICATIONS

Paper number: T41-3
Program: Technical Sessions
Time: 1:55 PM – 2:10 PM

Authors

Abstract

The transfer of Raman Spectra fiber optic distributed temperature sensing (DTS) from industrial applications (oil and gas, electric utilities, fire protection) to environmental monitoring (stream/groundwater interactions, limnology, dam seepage, snow hydrology, soil moisture, etc.) has only recently begun. We report on the results of a week-long DTS campaign designed to test the applicability of commercial DTS units for hydrologic applications and to investigate appropriate designs for installations in streams, lakes and soil. A combination of laboratory testing at the University of Nevada, Reno and fiber optic cable installation in Lake Tahoe were used as test beds for three commercially available DTS units and 4 different fiber optic cables. Results showed that temperature precision from 30 minute readings could be as low as +/-0.05 oC over cable lengths of up to 1 km. The importance of several field methods emerged: cable terminations and connectors can introduce temperature artifacts that vary in time; the use of known temperature baths during cable calibration is essential to obtain accuracy better than 1 oC; and double ended measurements, in which the illuminating laser is sequentially fired into both ends of the monitoring cable, both improved temperature resolution and eliminated artifacts from cable impingements that would be highly problematic for many hydrologic applications.

The results reiterated the significant potential for DTS systems to monitor hydrologic systems at temporal and spatial scales that were previously considered impossible and beyond the reach of most hydrologists, as well as the importance of attention to detail in field implementation.