Algorithm for Measuring Water Content and Salinity in Regions of High Salinity

Time Domain Reflectometry (TDR) is becoming a popular method of measuring water content. By measuring the time it takes for a step-waveform to propagate down and back an open circuited transmission line, one can determine the dielectric constant of the media. Regression equations can then be used to determine water content from the dielectric constant. Problems occur, however, in regions of high salinity (or electrical conductivity) in that the phase velocity and attenuation of electromagnetic waves as well as the characteristic impedance of the transmission lines are functions of frequency as opposed to constants. This results in dispersion of the low frequency components and attenuation of the high frequency components of a TDR step-waveform which causes errors in the determination of water content. This Phase I research project will investigate using existing electromagnetic and soil physics models to develop an algorithm to enable TDR systems to accurately measure water content and salinity over a wide range of water contents, salinities and soil types with a minimum amount of calibration.