Streambed Flux Measurement Informed by Distributed Temperature Sensing Leads to a Significantly Different Characterization of Groundwater Discharge

Groundwater discharge though streambeds is often focused toward discrete zones, indicating that preliminary reconnaissance may be useful for capturing the full spectrum of groundwater discharge rates using point-scale quantitative methods. However, many direct-contact reconnaissance techniques can b...

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Bibliographic Details
Published in:	Water (Basel) 2019-11, Vol.11 (11), p.2312
Main Authors:	Gilmore, Troy E., Johnson, Mason, Korus, Jesse, Mittelstet, Aaron, Briggs, Marty A., Zlotnik, Vitaly, Corcoran, Sydney
Format:	Article
Language:	eng
Subjects:	Anomalies Aquifers Cables Creeks & streams distributed–temperature sensing Estimates Fiber optics Fluxes Groundwater Groundwater discharge groundwater–surface water interaction Hydraulics hyporheic zone Locations (working) Measurement Permeability Reconnaissance Remote sensing Rivers Sampling Seepages Solutes Streambeds Surface water Surface-groundwater relations Temperature Water circulation Water column Water exchange
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Summary:	Groundwater discharge though streambeds is often focused toward discrete zones, indicating that preliminary reconnaissance may be useful for capturing the full spectrum of groundwater discharge rates using point-scale quantitative methods. However, many direct-contact reconnaissance techniques can be time-consuming, and remote sensing (e.g., thermal infrared) typically does not penetrate the water column to locate submerged seepages. In this study, we tested whether dozens of groundwater discharge measurements made at “uninformed” (i.e., selected without knowledge on high-resolution temperature variations at the streambed) point locations along a reach would yield significantly different Darcy-based groundwater discharge rates when compared with “informed” measurements, focused at streambed thermal anomalies that were identified a priori using fiber-optic distributed temperature sensing (FO-DTS). A non-parametric U-test showed a significant difference between median discharge rates for uninformed (0.05 m·day−1; n = 30) and informed (0.17 m·day−1; n = 20) measurement locations. Mean values followed a similar pattern (0.12 versus 0.27 m·day−1), and frequency distributions for uninformed and informed measurements were also significantly different based on a Kolmogorov–Smirnov test. Results suggest that even using a quick “snapshot-in-time” field analysis of FO-DTS data can be useful in streambeds with groundwater discharge rates
ISSN:	2073-4441 2073-4441