Application of Shortwave Infrared Imaging for Estimation of Soil Water Content and Flux Profiles.

A novel approach for determination of high resolution soil water content and water flux profiles under laboratory conditions is introduced. Constant-head upward flow experiments were performed on various soils packed into quartz Hele-Shaw cells. Soil profile during the experiments was imaged at high temporal frequency with a shortwave infrared (SWIR) camera in the 900-1700 nm electromagnetic domain. The SWIR reflectance recorded for each spatial pixel was converted to soil water content with a linear physically-based model. The obtained moisture profiles were in reasonable agreement with soil moisture data independently measured with a recently developed time domain reflectometry (TDR) sensor array with 1-cm depth resolution. The high spatial (i.e., 0.3 mm) and temporal (i.e., 1 min) SWIR reflectance-derived moisture profiles allowed calculation of water flux, which provides a potential new avenue for rapid estimation of soil hydraulic properties via inverse numerical modeling or analytical solutions.