A TDR array probe for monitoring near-surface soil moisture distribution

Wenyi Sheng, Rong Zhou, Morteza Sadeghi, Ebrahim Babaeian, David A. Robinson, Markus Tuller, Scott B. Jones

Research output: Contribution to journalArticle

  • 1 Citations

Abstract

Near-surface soil conditions (i.e., moisture and temperature) moderate mass and energy exchange at the soil–atmosphere interface. While remote sensing offers an effective means for mapping near-surface moisture content across large areas, in situ measurements, targeting those specific remotely sensed soil depths, are poorly understood and high-resolution near-surface measurement capabilities are lacking. Time domain reflectometry (TDR) is a well-established, accurate measurement method for soil dielectric permittivity and moisture content. A TDR array was designed to provide centimeter-resolution measurements of near-surface soil moisture. The array consists of nine stainless steel TDR rods spaced 1 cm apart, acting as waveguide pairs to form eight two-rod TDR probes in series. A critical aspect of the design was matching the spacing of the coaxial cable–TDR rod transition to avoid unwanted reflections in the waveforms. The accuracy of the TDR array permittivity measurement (±1 permittivity unit) was similar to that of conventional TDR as verified in dielectric liquids. Electric field numerical simulations showed minimal influence of adjacent rods during a given rod-pair measurement. The evaporation rate determined by the TDR array compared well with mass balance data in a laboratory test. Near-surface soil moisture profile dynamics were monitored at centimeter-depth resolution using the TDR array in a field experiment where volumetric moisture content estimates (0–8 cm) were within 2% of conventional three-rod TDR probes averaging across 0 to 8 cm and from 1- to 3-cm depths.

LanguageEnglish (US)
JournalVadose Zone Journal
Volume16
Issue number4
DOIs
StatePublished - Apr 1 2017

Fingerprint

time domain reflectometry
probes (equipment)
soil moisture
probe
soil water
monitoring
permittivity
moisture content
water content
soil-atmosphere interactions
distribution
evaporation rate
cables (equipment)
measurement method
stainless steel
electric field
energy transfer
cable
soil depth
in situ measurement

ASJC Scopus subject areas

  • Soil Science

Cite this

Sheng, W., Zhou, R., Sadeghi, M., Babaeian, E., Robinson, D. A., Tuller, M., & Jones, S. B. (2017). A TDR array probe for monitoring near-surface soil moisture distribution. Vadose Zone Journal, 16(4). DOI: 10.2136/vzj2016.11.0112

A TDR array probe for monitoring near-surface soil moisture distribution. / Sheng, Wenyi; Zhou, Rong; Sadeghi, Morteza; Babaeian, Ebrahim; Robinson, David A.; Tuller, Markus; Jones, Scott B.

In: Vadose Zone Journal, Vol. 16, No. 4, 01.04.2017.

Research output: Contribution to journalArticle

Sheng, W, Zhou, R, Sadeghi, M, Babaeian, E, Robinson, DA, Tuller, M & Jones, SB 2017, 'A TDR array probe for monitoring near-surface soil moisture distribution' Vadose Zone Journal, vol. 16, no. 4. DOI: 10.2136/vzj2016.11.0112
Sheng W, Zhou R, Sadeghi M, Babaeian E, Robinson DA, Tuller M et al. A TDR array probe for monitoring near-surface soil moisture distribution. Vadose Zone Journal. 2017 Apr 1;16(4). Available from, DOI: 10.2136/vzj2016.11.0112
Sheng, Wenyi ; Zhou, Rong ; Sadeghi, Morteza ; Babaeian, Ebrahim ; Robinson, David A. ; Tuller, Markus ; Jones, Scott B./ A TDR array probe for monitoring near-surface soil moisture distribution. In: Vadose Zone Journal. 2017 ; Vol. 16, No. 4.
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