Application of Shortwave Infrared Imaging for Estimation of Soil Hydraulic Properties.

A novel laboratory method for cost- and time-efficient estimation of the soil water characteristic (SWC) curve and the unsaturated hydraulic conductivity, K(h), function will be presented. Constant flux water distribution was imaged with a Shortwave Infrared (SWIR) line scan camera and the obtained high resolution reflectance maps were converted to surface water content with a physically-based optical model. The surface moisture information together with the applied constant flux boundary and the geometrical container dimensions were applied for inverse estimation of the SWC and K(h) functions with HYDRUS-2D/3D. While the forward simulations were performed with HYDRUS, the optimization was executed with the Matlab Global Optimization Toolbox. The results obtained for soils spanning the full textural range show reasonable agreement with independently measured SWC and saturated hydraulic conductivity data, demonstrating the feasibility of the approach for time efficient estimation of soil hydraulic properties. An appealing feature of the developed methodology is its ability to predict the wetting as well as the drying branches of the SWC.