The presence and movement of groundwater results in heat transport and moreover in temperature distribution in soil. The temperature can be measured continuously along a fibre optic cable up to a few kilometres in length and with high accuracy by using the technology of Distributed Fibre Optic Temperature measurements (DFOT). This paper shows the prospects of DFOT in combination with the heat-up method for monitoring infiltration processes, changes in groundwater table and groundwater flow velocity as well as the theoretical basis of the measurement technique, the fundamental procedure and results from extensive experimental investigations. It also gives insight in the thermodynamic theory which rules the convection from heated cylinders in cross flow. Furthermore, tests are presented that prove the applicability of the heat-up method to measure the velocity of flow through porous media in-situ. Keywords: distributed seepage velocity measurement; filter velocity; monitoring

The presence and movement of groundwater results in heat transport and moreover in temperature distribution in soil. The temperature can be measured continuously along a fibre optic cable up to a few kilometres in length and with high accuracy by using the technology of Distributed Fibre Optic Tempe...