THE APPLICATION OF TDR IN LABORATORY COLUMN EXPERIMENTS

An automated TDR system was used together with an automated tensiomete r system in laboratory column experiments for the measurement of unsat urated hydraulic properties of soils. The laboratory experiments were a stationary flux (sprinkling infiltrometer) carried out with differen t fluxes, and a transient (evaporation) method. Simultaneous measureme nts of water content and pressure head give the water retention charac teristic and enable the application of the instantaneous profile analy sis for calculating the hydraulic conductivity. This direct analysis i s compared with the traditional analysis methods normally used for the laboratory experiments. The application of automated measurement tech niques and the use of TDR increases the speed of the measurements, gen erates more data points and requires less assumptions in the data anal ysis. Moreover, TDR measurements give insight in the flow process, inc luding effects of hysteresis and heterogeneity within a sample. Perfor ming the sprinkling infiltrometer and evaporation experiments on the s ame sample enables the determination of the unsaturated hydraulic cond uctivity at pressure heads ranging from -0.01 m to -6 m.