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A new approach for groundwater fluxes assessment in alluvial aquifers using active-DTS with a Brillouin-based sensor.

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Title: A new approach for groundwater fluxes assessment in alluvial aquifers using active-DTS with a Brillouin-based sensor.
Authors: Labbe, Jordan1 (AUTHOR) jordan.labbe@univ-fcomte.fr, Romanet, Maxime2 (AUTHOR), Celle, Hélène1 (AUTHOR), Zerbib, Maxime2 (AUTHOR), Huy, Kien Phan2,3 (AUTHOR), Matic, Alexandre2 (AUTHOR), Klaba, Victor1 (AUTHOR), Mailhot, Gilles4 (AUTHOR), Beugnot, Jean-Charles2 (AUTHOR)
Source: Journal of Hydrology. Jul2026, Vol. 673, pN.PAG-N.PAG. 1p.
Subjects: Aquifers, Brillouin scattering, Groundwater flow, Raman spectroscopy
Abstract: Fiber optic distributed temperature sensing has become a widely used approach to estimate groundwater fluxes in various hydrogeological contexts. Raman-based sensors are the most commonly adopted DTS units but they rely on calibration baths that may be challenging to maintain for experiments extending over several days. In this paper, a novel method using a Brillouin-based sensor (DITEST) is proposed. This approach relies on the linear relationship between the Brillouin Frequency Shift and the fiber temperature which is not affected by optical losses. The proposed methodology was tested at the experimental site of Port-Douvot where an Electrical Resistivity Tomography profile and a core sample were conducted to assess vertical and lateral heterogeneities. These investigations have identified that the alluvial deposits extend to an average thickness of 10 m with a top layer of clayey sands (∼5 m) overlying a second layer of coarse gravel and pebbles (∼5 m). Point Dilution Tests were carried out to investigate the range of possible groundwater fluxes q , the results of which have revealed fluxes ranging from 1.2 × 10−5 to 8.2 × 10−7 m/s. Brillouin active-DTS measurements were conducted with a spatial resolution of 1 m, a sampling interval of 0.25 m and a temperature sensitivity of 0.2°C. The vertical variations of horizontal groundwater fluxes q are consistent with subsurface heterogeneities. Estimated fluxes spanned a shorter interval than Point Dilution Tests, between 1.0 × 10−7 to 7.0 × 10−7 m/s, but remain plausible. The fact that frequency measurements are absolute and do not require any field calibration makes Brillouin sensing an attractive tool for long-term monitoring. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:Fiber optic distributed temperature sensing has become a widely used approach to estimate groundwater fluxes in various hydrogeological contexts. Raman-based sensors are the most commonly adopted DTS units but they rely on calibration baths that may be challenging to maintain for experiments extending over several days. In this paper, a novel method using a Brillouin-based sensor (DITEST) is proposed. This approach relies on the linear relationship between the Brillouin Frequency Shift and the fiber temperature which is not affected by optical losses. The proposed methodology was tested at the experimental site of Port-Douvot where an Electrical Resistivity Tomography profile and a core sample were conducted to assess vertical and lateral heterogeneities. These investigations have identified that the alluvial deposits extend to an average thickness of 10 m with a top layer of clayey sands (∼5 m) overlying a second layer of coarse gravel and pebbles (∼5 m). Point Dilution Tests were carried out to investigate the range of possible groundwater fluxes q , the results of which have revealed fluxes ranging from 1.2 × 10−5 to 8.2 × 10−7 m/s. Brillouin active-DTS measurements were conducted with a spatial resolution of 1 m, a sampling interval of 0.25 m and a temperature sensitivity of 0.2°C. The vertical variations of horizontal groundwater fluxes q are consistent with subsurface heterogeneities. Estimated fluxes spanned a shorter interval than Point Dilution Tests, between 1.0 × 10−7 to 7.0 × 10−7 m/s, but remain plausible. The fact that frequency measurements are absolute and do not require any field calibration makes Brillouin sensing an attractive tool for long-term monitoring. [ABSTRACT FROM AUTHOR]
ISSN:00221694
DOI:10.1016/j.jhydrol.2026.135336