Spatial Time Domain Reflectometry (spatial TDR) in geo-environmental engineering

Spatial Time Domain Reflectometry (spatial TDR) is a measurement method for determining water content profiles along electrically insulated probes (transmission lines). The method is based on the inverse modeling of TDR reflectograms using an optimisation algorithm. By means of using flat ribbon cables as sensors it is possible to take two independent TDR reflectograms from both ends of the probe, which are used to improve the spatial information content of the optimisation results and to consider effects caused by electrical conductivity. The method has been used for different geo-environmental purposes, such as the monitoring of water content distributions on a sand island for investigating groundwater recharge processes and the monitoring of a mine waste cover.