Fiber Optics Distributed Temperature Sensing (FO-DTS) for Long-term Monitoring of Soil Water Changes in the Subsoil

This study investigates the temperature changes over the time in the vadose zone by FO-DTS at high spatial and temporal frequency. It buried at 0.05, 0.10 and 0.15 m of depth and at the soil surface along a 60 m profile is used. Soil temperature is measured every 6 minutes at a spatial resolution of 0.5 m using a double-ended configuration. This research aims to interpret the temperature in order to disclose the soil water changes in subsoil. The monitoring site is the Draix-Bleone catchment in the South French Alps, mainly composed of weathered clay-shales and characterized by a heterogeneous clay-rich soil. Fiber optic cable was spread along 350 meter through three different soil unit consisting of argillaceous weathered black marls, silty colluvium under grass and silty colluvium under forest. This indirect measurement technique is promising for the future; some limitations in the measurements are also discussed.