Measurement of Water Content Profiles using Spatial Time Domain Reflectometry (spatial TDR)

摘要

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 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 purposes, such as monitoring water content distributions on a full scale dike model made of well-graded clean sand, the development of a flood warning system for small catchments with open ended 3-rod-probes and as a laboratory application for the investigation of water content dynamics in unsaturated soils. The contribution introduces the spatial TDR technology and presents results of different applications.