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MoisturEC: A New R Program for Moisture Content Estimation from Electrical Conductivity Data
Citation:
Terry, N., F. Day-Lewis, D Werkema, AND J. Lane. MoisturEC: A New R Program for Moisture Content Estimation from Electrical Conductivity Data. GROUNDWATER MONITORING AND REMEDIATION. National Ground Water Association, Westerville, OH, 56(5):823-831, (2018). https://doi.org/10.1111/gwat.12650
Impact/Purpose:
Geophysical inference of soil moisture is a longstanding problem in hydrogeophysics, with seminal papers going back several decades (LaBrecque et al., 1992; Sheets and Hendrickx, 1995) and petrophysical basis going back further (e.g., Archie, 1942). Whereas conventional measurements of moisture (e.g., time-domain reflectometry, tensiometer, neutron probe) are invasive and provide only local information at sparse locations, geophysical mapping of soil moisture can provide information non-invasively and over large areas; thus, geophysics offers potential to inform water management for agriculture, aquifer recharge, and landfill operations. A number of geophysical methods have sensitivity to soil moisture, including direct-current electrical, electromagnetic induction (EMI), nuclear magnetic resonance, ground penetrating radar, seismic, and time-lapse gravity. Here, we focus on the use of electrical conductivity (EC) as a proxy for moisture content (MC). EC can be measured using electrical or EMI methods, which allow for one-, two- or three-dimensional surveys. We present a new R program, MoisturEC, to facilitate the ‘translation’ of EC to moisture content, fill in gaps between measurement locations, and integrate geophysical measurements with direct measurements of EC at sparse locations. Although the petrophysical principles for this translation are well established (Archie, 1942; LaBrecque et al., 1992; Binley et al., 2006; Cassiani et al., 2006), the potential of geophysical mapping of MC has not 50 been fully realized for lack of straightforward software tools.
Description:
Non-invasive geophysical estimation of soil moisture has potential to improve understanding of flow in the unsaturated zone for problems involving agricultural management, aquifer recharge, and optimization of landfill design and operations. In principle, several geophysical techniques (e.g., electrical, electromagnetic induction, nuclear magnetic resonance) offer insight into soil moisture, but data-analysis tools are needed to ‘translate’ geophysical results into estimates of soil moisture, consistent with (1) the uncertainty of this translation and (2) any available direct measurements of moisture. Although geostatistical frameworks exist for this purpose, straightforward and user-friendly tools are required to fully capitalize on the potential of geophysical information for soil-moisture estimation. Here, we present MoisturEC, a simple R program with a graphical user interface to convert measurements or images of electrical conductivity (EC) to soil moisture. The program produces two- and three-dimensional images of moisture based on available EC and direct measurements of moisture, interpolating between measurement locations using a Tikhonov regularization approach.
URLs/Downloads:
DOI: MoisturEC: A New R Program for Moisture Content Estimation from Electrical Conductivity Data
https://onlinelibrary.wiley.com/doi/abs/10.1111/gwat.12650