Estimating soil moisture on a spatial and temporal scale beginning with temperature signals collected via Distributed Temperature Sensing

Distributed Temperature Sensing (DTS) allows for the nearly continuous measurement of temperature over both a spatial and temporal scale by use of standard fiber optic cables. Theoretically, measurement of temperature progression throughout a soil column can lead to estimates of bulk soil thermal properties. From these thermal properties, soil moisture estimates can then be achieved. In Yerington, Nevada, three fiber optic cables in a vertical profile have been plowed into the shallow subsurface. Passive temperature measurements were made every meter along the cable, and from these measurements thermal properties of the soil have been estimated. Soil samples co-located with the fiber optic cables were used in the lab to derive a relationship between water content and thermal conductivity, as well as to determine the bulk soil heat capacity. By combining these measurements, efforts have been made to accurately predict soil moisture on the spatial and temporal scales. Preliminary data shows the thermal response of the soil to change in accordance with both wetting and drying periods. The use of distributed temperature sensing allows for the assessment of soil moisture and soil thermal properties on scales otherwise very difficult to achieve with current techniques.