Spatial time domain reflectometry and its application for the measurement of water content distributions along flat ribbon cables in a full‐scale levee model

Abstract

[1] Spatial time domain reflectometry (spatial TDR) is a new measurement method for determining water content profiles along elongated probes (transmission lines). The method is based on the inverse modeling of TDR reflectograms using an optimization algorithm. By means of using flat ribbon cables it is possible to take two independent TDR measurements from both ends of the probe, which are used to improve the spatial information content of the optimization results and to consider effects caused by electrical conductivity. The method has been used for monitoring water content distributions on a full-scale levee model made of well-graded clean sand. Flood simulation tests, irrigation tests, and long-term observations were carried out on the model. The results show that spatial TDR is able to determine water content distributions with an accuracy of the spatial resolution of about ±3 cm compared to pore pressure measurements and an average deviation of ±2 vol % compared to measurements made using another independent TDR measurement system.

Coupled hydrogeophysical parameter estimation using a sequential Bayesian approach

“…At the foot of the landside slope, there is a drain that removes excess water and ensures the stability of the model dike. More details on the dike model can be found in Scheuermann et al (2009) and Rings et al (2008).…”

“…By applying a reconstruction algorithm (Schlaeger, 2005), permittivity profiles can be obtained along these cables. These can be converted to spatially resolved soil water content profiles by applying a petrophysical relationship, in this case a site-specific calibration (see Scheuermann et al, 2009). Fig.…”

Stabilisation of river dykes with drainage elements

“…5b). Multiple measurement devices such as TDR-Sensors (Scheuermann et al, 2001(Scheuermann et al, , 2008Woersching et al, 2006), tensiometers and a hydraulic gauge in the centre of the dyke permitted a spatial investigation of the seepage conditions inside the dyke structure. The positions of the measurement devices as well as installed drainage elements are shown in Fig.…”

A quality assessment of Spatial TDR soil moisture measurements in homogenous and heterogeneous media with laboratory experiments

“…The essential idea of Spatial TDR is to cluster several wave guides in a small area, operate them by a single sampling TDR and invert the reflectograms to elucidate the evolution of the soil moisture profile. Spatial TDR was originally proposed by Schlaeger (2005) and further tested by Scheuermann et al (2009) to monitor moisture in sandy dams. The reflectogram of the TDR measurement is influenced by the probe geometry (Bänninger et al, 2008;Spittlehouse, 2000), solids in the sphere of influence (Knight et al, 1997), layered soils (Greco, 2008) or energy dissipation along the probe due to clay and salinity (Jones and Or, 2004;Chen et al, 2007;Kupfer et al, 2007).…”