ORIGINAL RESEARCH article
Front. Water
Sec. Water and Critical Zone
Volume 7 - 2025 | doi: 10.3389/frwa.2025.1574618
This article is part of the Research TopicUtilizing Well-Instrumented Critical Zone Sites: Infrastructure, Data Integration, and Advancements in Earth System ResearchView all articles
PASSIVELY HEATED FIBER OPTIC DISTRIBUTED TEMPERATURE SENSING FOR LONG-TERM SOIL MOISTURE OBSERVATIONS
Provisionally accepted
- 1Padjadjaran University, Bandung, Indonesia
- 2Department of Geophysics, Universitas Padjadjaran, Sumedang, West Java, Indonesia
- 3Institut Terre et Environnement de Strasbourg, Université de Strasbourg, Strasbourg, Alsace, France
- 4UMR7154 Institut de Physique du Globe de Paris (IPGP), Paris, Île-de-France, France
- 5INRA UMR Environnement Méditerranéen et Modélisation des Agro-Hydrosystèmes, Avignon, Provence-Alpes-Côte d'Azur, France
- 6IRIS-Instruments, Orléans, France
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This paper presents a strategy to improve spatial and temporal volumetric water content (VWC) using passive DTS observation. We demonstrate this method using 22 months of passive fiber optic distributed temperature (FO-DTS). This method has previously encountered challenges, primarily due to noise effects and instability of diurnal temperature. We improve the water traceability by employing numerical estimation of the soil thermal diffusivity. This method was tested on a slope catena at the Draix-Bléone Mediterranean catchment (South-East France) and with synthetic data prior to applying it to field-scale scenarios. The results show a good performance as indicated by a determination coefficient of 0.92, a root mean square error of 0.06 m³/m³ and a mean relative percentage error of 1.41%. We conclude that the proposed strategy is convenient for analyzing passive DTS experiments using diurnal heat sources, where reliable thermal diffusivity and VWC data can be obtained without the use of active application sources. 1 Deleted: R 89 Deleted: FO-DTS temperature measurements use many other 90 scatterings such as Brilloin and Raman scattering. Raman scattering 91 in the optical fiber to achieve a temperature resolution as small as ± 92 0.01°C. Deleted: One of the common approaches for calculating VWC 139 involves data assimilation, utilizing temperature measurements to 140 determine VWC. This method ensures the accuracy of the results by 141 incorporating correlations between temperature and soil moisture in 142 the shallow soil layers 143 Deleted: 144 Deleted: A second, approach is to estimate soil VWC using thermal 145 diffusivity by solving the heat transfer equation 146 Deleted: Therefore, diffusivity estimated from time resolution 147 techniques can only be used to determine daily values of VWC.
Keywords: Passive DTS, soil moisture, Thermal diffusivity, HYDRUS, VWC
Received: 11 Feb 2025; Accepted: 19 Jun 2025.
Copyright: © 2025 Susanto, Malet, Chavanne, Marc and Gance. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Kusnahadi Susanto, Padjadjaran University, Bandung, Indonesia
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