Adapting HYDRUS-1D to simulate the transport of soil water isotopes with evaporation fractionation

Ecohydrological processes are often evaluated by studying the fate of stable water isotopes. However, isotopic fractionation during evaporation is ignored or simplified in current models, resulting simulation errors that may be propagated into practical applications isotope tracing. In this study, we adapted and tested HYDRUS-1D model, a numerical model widely used to simulate variably-saturated flow solute transport porous media, including an option while accounting for fractionation. The results obtained were excellent agreement with existing analytical solutions. Additional plausibility tests field evaluation further demonstrated model's accuracy. A simple particle tracking algorithm was also implemented calculate soil water's transit times validate modified results. Transit calculated module (PTM) similar those estimated peak displacement method, validating applicability PTM. developed represents comprehensive tool numerically investigate many important research problems involving critical zone.