Fibre optic distributed temperature sensing (DTS) is used increasingly for environmental monitoring and subsurface characterisation. Combined with heating of metal elements embedded within the fibre optic cable, the temperature response of the soil provides valuable information from which soil parameters such as thermal conductivity and soil moisture can be derived at high spatial and temporal resolution, and over long distances.

In this manuscript, we present a novel Active Distributed Temperature Sensing (A-DTS) system and its application to characterise spatial and temporal dynamics in soil thermal conductivity along a recently forested hillslope in Central England, UK. Compared to conventional techniques (needles prob surveys), A-DTS provided values with similar spread though lower on average. The larger number of measurement points that A-DTS provides at higher spatial and temporal resolutions, the ability to repeat surveys under different meteorological/hydrological conditions allows for a more detailed examination of the spatial and temporal variability of thermal conductivities at the study site. Although system deployment time and costs are higher than with needle probes, A-DTS can be extremely appealing to applications requiring (1) long term monitoring, (2) at high temporal repeatability, (3) over long (km) distances and with (4) minimum soil disturbance, rather than one-off spatial surveys.

Thematic collection: This article is part of the Measurement and monitoring collection available at: https://www.lyellcollection.org/cc/measurement-and-monitoring

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