Presentation Type

Poster

Abstract

In this study, skin temperature measured with a thermal infrared (TIR) camera was used to estimate soil hydraulic parameters. These are the physical properties that control how soils transport and retain water, which are notoriously difficult to measure in the field due to the extreme spatial variability of their values. Laboratory experiments were set up to record surface skin temperature response in a clean soil column using a TIR camera after an artificial wetting event. An array of thermocouples, a net radiometer, heat flux sensor and weather station were used to constrain the TIR data and the energy budget during the experiment. The soil column surface was then wetted with a known amount of water over a controlled time period and the thermal response recorded at five minute intervals over the course of 18 hours. Soil hydraulic parameters were then estimated by fitting a water-energy conservation model (ECH2O) to the observed data using a Levenberg-Marquardt least squares minimization. This inversion of ECH2O was able to estimate soil air entry pressure, soil porosity, and the Brooks-Corey pore size distribution parameter with a relatively high degree of precision. The estimated parameters were compared to several sets of known values based on soil textural classification. Most of the estimates were within the range of standard published values. These results show that soil hydraulic parameter estimation based on TIR skin temperature data could prove to be a fast and useful new tool to characterize the distribution and spatial heterogeneity in soil hydraulic properties at the field scale.

Category

Physical Sciences

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Apr 28th, 11:00 AM Apr 28th, 12:00 PM

Using Thermal Infrared Imaging to Estimate Soil Hydraulic Parameters: A Novel Approach

UC South Ballroom

In this study, skin temperature measured with a thermal infrared (TIR) camera was used to estimate soil hydraulic parameters. These are the physical properties that control how soils transport and retain water, which are notoriously difficult to measure in the field due to the extreme spatial variability of their values. Laboratory experiments were set up to record surface skin temperature response in a clean soil column using a TIR camera after an artificial wetting event. An array of thermocouples, a net radiometer, heat flux sensor and weather station were used to constrain the TIR data and the energy budget during the experiment. The soil column surface was then wetted with a known amount of water over a controlled time period and the thermal response recorded at five minute intervals over the course of 18 hours. Soil hydraulic parameters were then estimated by fitting a water-energy conservation model (ECH2O) to the observed data using a Levenberg-Marquardt least squares minimization. This inversion of ECH2O was able to estimate soil air entry pressure, soil porosity, and the Brooks-Corey pore size distribution parameter with a relatively high degree of precision. The estimated parameters were compared to several sets of known values based on soil textural classification. Most of the estimates were within the range of standard published values. These results show that soil hydraulic parameter estimation based on TIR skin temperature data could prove to be a fast and useful new tool to characterize the distribution and spatial heterogeneity in soil hydraulic properties at the field scale.