Development of a vertical TDR probe to measure the water content profile with depth in peat columns

Time Domain Reflectometry (TDR) is used to monitor the moisture content in soils including peat. The objective of this research was to develop a TDR probe to measure the vertical moisture profile in a peat biofilter operating in the field where access to the filter is limited to the top surface.; The application of TDR to measure the water content in soils has been demonstrated by many researchers. In this research, it was demonstrated that a vertical TDR probe advanced to various depths estimated similar water content profiles with depth in peat columns compared to horizontal TDR measurements. The experiment was carried out in six columns exposed to a sequential water drainage process and two columns exposed to an organic loading to simulate a clogging process. Water content in peat columns was measured using both the vertical and horizontal TDR probes, and the gravimetric method. Water contents determined by the vertical and horizontal probes agreed well. The data was slightly more scattered in the clogging columns due to TDR signal attenuation. Total signal attenuation was observed with longer probes in clogged peat soils.; There is a consistent discrepancy between the TDR measured water contents and those determined gravimetrically, which is believed to be caused by a systematic error related to the TDR calibration curve.