Journal ArticleDOI
Calibration of time domain reflectometry for water content measurement using a composite dielectric approach
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TLDR
In this paper, a calibration curve for the TDR method is presented which is not restricted to specific soil conditions, based on the dielectric mixing model of Dobson et al. (1985).Abstract:
Time domain reflectometry (TDR) has been developed to an operational level for the measurement of soil water content during the past decade. Because it is able to provide fast, precise and nondestructive in situ measurements, it has become an alternative to the neutron scattering method, in particular for monitoring water content under field conditions. One of the major disadvantages of the neutron scattering technique is that, due to the relatively high sensitivity of the signal to factors other than water content, site-specific calibration is usually required. In this paper a calibration curve for the TDR method is presented which is not restricted to specific soil conditions. The calibration is based on the dielectric mixing model of Dobson et al. (1985). Measurements of volumetric water content and dielectric number at eleven different field sites representing a wide range of soil types were used to determine the parameter of the model by weighted nonlinear regression. The uncertainty (root mean square error) of water content values calculated with the optimized calibration curve was estimated not to exceed 0.013 cm3/cm3. This value is comparable to the precision of the thermogravimetric method. From a sensitivity analysis it was determined that the temperature dependence of the TDR signal may have to be corrected to obtain optimum accuracy.read more
Citations
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Susceptibility of soils to preferential flow of water : a field study
TL;DR: In this article, the effect of initial water content on the flow patterns of water and solutes in soils was investigated. But the initial water contents had a less pronounced effect in some soils and no effect in others, and the spatial structure of flow patterns showed remarkable differences.
Journal ArticleDOI
Measuring Soil Water Content with Ground Penetrating Radar: A Review
TL;DR: A comprehensive review of methods to measure soil water content with ground penetrating radar (GPR) is presented in this article, where the authors distinguish four methods: reflected wave velocity, ground wave velocity and surface reflection coefficient.
Journal ArticleDOI
Measuring Soil Water Content with Ground Penetrating Radar
TL;DR: In this paper, a comprehensive review of methods to measure soil water content with ground penetrating radar (GPR) is presented, which distinguishes four methodologies: reflected wave velocity, ground wave velocity and surface reflection coefficient.
Journal ArticleDOI
Measurement of soil water content and electrical conductivity by time domain reflectometry: a review
TL;DR: An overview of theoretical background for measuring water content and electrical conductivity is presented as well as characteristics of different types of probes in this article, and limitations of applying TDR techniques to measuring soil water and salinity are also addressed.
Journal ArticleDOI
On the spatio-temporal dynamics of soil moisture at the field scale
Harry Vereecken,Johan Alexander Huisman,Yakov Pachepsky,Carsten Montzka,J. van der Kruk,Heye Bogena,Lutz Weihermüller,Michael Herbst,Gonzalo Martinez,Jan Vanderborght +9 more
TL;DR: In this paper, the authors review the state of the art of characterizing and analyzing spatio-temporal dynamics of soil moisture content at the field scale and discuss measurement techniques that have become available in recent years and that provide unique opportunities to characterize field scale soil moisture variability with high spatial and temporal resolution.
References
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Numerical Recipes, The Art of Scientific Computing
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Electromagnetic determination of soil water content: Measurements in coaxial transmission lines
TL;DR: The dependence of the dielectric constant, at frequencies between 1 MHz and 1 GHz, on the volumetric water content is determined empirically in the laboratory as discussed by the authors, and the effect of varying the texture, bulk density, temperature, and soluble salt content on this relationship was also determined.
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Classical Electrodynamics (2nd edn)
TL;DR: The present edition of this now classic text offers substantial refinements and improvements over the first edition and includes some new material as mentioned in this paper, including an improved derivation of the macroscopic equations, monopoles, causality and dispersion relations, signal propagation in a dispersive media.
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Microwave Dielectric Behavior of Wet Soil-Part II: Dielectric Mixing Models
TL;DR: In this paper, the authors evaluated the microwave dielectric behavior of soil-water mixtures as a function of water content and soil textural composition for the 1.4-to 18-GHz region.
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Microwave Dielectric Behavior of Wet Soil-Part 1: Empirical Models and Experimental Observations
TL;DR: In this article, the authors evaluate the microwave dielectric behavior of soil-water mixtures as a function of water content, temperature, and soil textural composition, and present two mixing models to account for the observed behavior: 1) a semi-empirical refractive mixing model that accurately describes the data and requires only volumetric moisture and soil texture as inputs, and 2) a theoretical four-component mixing model explicitly accounts for the presence of bound water.