Deriving and validating parametric spectrotransfer functions for estimating soil hydraulic properties in VIS-NIR-SWIR range

Soil hydraulic properties are very important in hydrological cycle. The objective of this study was to explore the feasibility of estimating soil hydraulic parameters using diffused spectral reflectance data in visible، near-infrared and short-wave infra-red (350-2500 nm) ranges. Consequently، hyper-spectral reflectance of some soil samples was measured using a handheld spectroradiometer. After preprocessing the spectra، correlation between spectral data in each wavelength and Mualem van Genuchten hydraulic parameters (، n and Ks*) were explored. Using stepwise multiple regression method، parametric spectro-transfer functions (PSTFs) were derived. According to the results، the largest correlation coefficients were obtained for and n at wavelengths 550 and 2300 nm، while Ks* parameter showed maximum correlation at wavelength 1927 nm. The parametric STFs showed similar results for (R=0. 54) and n (R=0. 58). The best results were obtained for Ks* parameterwith R values equal to 0. 76. The parametric STFs provided mean RMSR values of 0. 017 cm3 cm-3 for all the pressure heads. Although the performance for MvG parameters was not very high، this approach can be considered as a novel application of soil spectroscopy and might be used as a useful indirect method for estimating soil hydraulic properties.