Assessing groundwater discharge to streams with distributed temperature sensing technology Birkham, T.; Barbour, S. Lee; Goodbrand, A.; Tallon, L. K.; Szmigielski, J.; Klein, R.
Characterization of the interactions of groundwater with surface stream water is fundamental to understanding and managing stream water quality in natural and altered watersheds. The spatial and temporal variability in the exchange of water and solutes across the streambed affects stream water quality evolution along the channel length, especially in coarse-grained alluvial sediments. Identifying and delineating areas of groundwater discharge has the potential to inform water quality management strategies including the location and design of intake structures, groundwater cut-off systems, or permeable reactive barriers. Distributed temperature sensing (DTS) is an emerging technology that has found wide application in stream hydrology. A DTS system integrates a fibre-optic (FO) cable to measure continuous temperature profiles (manufacture reported accuracy of ±1 °C and resolution of ±0.01 °C) with spatial resolutions of 1 m or better over distances of up to several kilometres. In September 2013, a DTS cable was installed in a predominantly coarse-textured stream channel at a coal mining operation in the Elk Valley of British Columbia. The objective was to evaluate the utility of a FO DTS system in a location where identification of groundwater discharges to a stream was being studied as part of Teck Resources Limited (Teck) applied research and development program focused on managing water quality in mine watersheds. This study was intended as a verification of methods for in-stream DTS installation and measurements with recommendations made for improved calibration procedures. Temperature was measured along a 160-m stretch of stream and streambed at 20 minute sampling intervals using a 5 minute signal integration time over six days. In-stream DTS measurements were successful in delineating a localized area of lower temperature identified as a groundwater discharge zone. The measurement of cooler groundwater discharge in the streambed relative to the stream was corroborated by the presence of well-established riparian vegetation and a streambank seep.
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