Modeling vapor transfer in soil water and heat simulations – a modularized, partially-coupled approach

Authors: WANG, ZHUANGJI - University Of Maryland; Timlin, Dennis; Fleisher, David; SUN, WENGUANG - University Of Nebraska; BEEGUM, SAHILA - University Of Nebraska; LI, SANAI - Oak Ridge Institute For Science And Education (ORISE); CHEN, YAN - China Agriculture University; Reddy, Vangimalla; TULLY, KATHERINE - University Of Maryland; HORTON, ROBERT - Iowa State University

Submitted to: Journal of Hydrology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/24/2022
Publication Date: 1/31/2022
Citation: Wang, Z., Timlin, D.J., Fleisher, D.H., Sun, W., Beegum, S., Li, S., Chen, Y., Reddy, V., Tully, K., Horton, R. 2022. Modeling vapor transfer in soil water and heat simulations – a modularized, partially-coupled approach. Journal of Hydrology. 608:127541. https://doi.org/10.1016/j.jhydrol.2022.127541.
DOI: https://doi.org/10.1016/j.jhydrol.2022.127541

Interpretive Summary: In soil, water can evaporate in the warm areas, move to colder zones, and then condense. Such a process can be a predominant component of soil water transfer when the soil is relatively dry. Our objective is to add vapor transport to a computer model called 2DSOIL that simulates water, chemical and temperature dynamics in soil. Directly adding vapor transport to the 2DSOIL water and heat modules however may induce substantial modifications to the computer code of these modules. Therefore, we implement vapor transfer as a separate “corrector” that can be embedded in 2DSOIL without major revisions to the original 2DSOIL code. This implementation does not impact performance. Here we show how the addition of vapor transport to 2DSOIL affects evaporation of water where the soil is covered by plant residues and also left uncovered. This research is useful to soil scientists, hydrologists, agronomists, and agricultural managers interested in quantifying evaporation, plant water uptake and drainage of water input into soil as irrigation or rainfall.

Technical Abstract: Coupled water and heat transfer models are widely used to analyze soil water content and temperature dynamics, evaluate agricultural management systems, and support crop growth modelling. In relatively dry soils, vapor transfer, rather than liquid water flux, becomes the main pathway for water redistribution. However, in some modularized soil simulators, e.g., 2DSOIL, vapor transfer is not included. Directly embedding vapor transfer into existing water and heat transfer modules may violate the modularized architecture of those simulators. Therefore, the objectives of this study are to design a vapor transfer model, evaluate its performance, and apply it in a soil water and heat simulator, e.g., 2DSOIL, as a separate module. The efficacy of the vapor transfer model is evaluated by comparing the simulated soil water content and temperature before and after implementing the proposed vapor transfer model, and the soil water content and temperature simulated with the standard Philip and de Vries (1957) model. By implementing vapor transfer as a separate module in 2DSOIL, modifications to existing water and heat transfer modules can be minimized and the modularized model architecture can be maintained. Numerical examples of 2DSOIL with the proposed vapor transfer model are presented to illustrate the effects of vapor flux on soil water and temperature redistributions. In conclusion, the proposed vapor transfer model provides an accurate and easy-to-use method to account for the effects of vapor transfer on soil water and heat simulations.