Non-Invasive Detection of Soil Moisture in Wet Vertisols Using Electrical Resistivity Tomography
Abstract
The unique characteristics of Vertisols complicate soil moisture measurements
and often obscure traditional markers of wetland soils, which may result in failure to
identify jurisdictional wetlands. Electrical Resistivity Tomography (ERT) has been
proposed for non-invasive measurement and temporal monitoring of soil moisture in
Vertisols. Resistivity measurements were conducted on two Texas Vertisols: a Typic
Hapludert and a Chromic Haplustert. Water and clay content were determined from soil
cores taken from corresponding ERT transects. Multiple linear regression models
predicting volumetric water content from log resistivity and clay content indicate that
resistivity is, at best, a weak predictor of water content in high-clay soils (p-value ≥
0.03), while clay content is consistently highly significant (p-value < 0.001). Further,
regression models were site-specific. Regression of changes in log resistivity and water
content over time provides weak evidence that ERT may be used to monitor temporal
trends. Resistivity was a significant predictor of changes in water content (p-value <
0.001) in a limited area at one site where clay content was well-known and changes in
both resistivity and water content were large compared to other areas in the same site.
Changes in soil moisture cannot be accurately quantified from changes in resistivity in
wet Vertisols, though wetting and drying trends may be discernible. ERT data in wet
Vertisols are prone to noise that obscures the signal from soil moisture. Accordingly,
ERT is generally unfit for monitoring temporal changes in soil moisture in wet Vertisols.
Citation
Marley, Elizabeth Grace (2018). Non-Invasive Detection of Soil Moisture in Wet Vertisols Using Electrical Resistivity Tomography. Master's thesis, Texas A & M University. Available electronically from https : / /hdl .handle .net /1969 .1 /174141.