Staff Research Highlight - Effects of soil heterogeneity and preferential flow on the water flow and isotope transport in an experimental hillslope
Chen, X., Yu, Z., Yi, P., Hwang, H.-T., Sudicky, E. A., Tang, T., & Aldahan, A. (2024). Effects of soil heterogeneity and preferential flow on the water flow and isotope transport in an experimental hillslope. In Science of The Total Environment (Vol. 917, p. 170548). Elsevier BV. https://doi.org/10.1016/j.scitotenv.2024.170548
“HGS (HydroGeoSphere), a physically-based hydrological model, has been well developed in coupling variably-saturated subsurface and surface water flow as well as solute transport, and has been successfully applied in numerous applications.”
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We’re pleased to highlight this publication, co-authored by Aquanty’s senior scientist, Hyoun-Tae Hwang, focusing on the interplay between soil heterogeneity, preferential flow, and isotopic tracing to better understand water flow and transport dynamics in hillslope systems.
GRAPHICAL ABSTRACT
In this study, researchers applied HydroGeoSphere (HGS) to simulate coupled surface and subsurface water flow and isotope transport in an artificial hillslope environment. The research incorporated isotopic tracing experiments and high-resolution monitoring data to examine the impact of soil stratification and preferential flow paths on the movement and mixing of water within the hillslope.
The results revealed that vertical soil heterogeneity and lateral preferential flow significantly influence water transport pathways, flow velocities, and residence times. For instance, stratified soil layers showed distinct variations in moisture retention and flow dynamics, while preferential flow accelerated lateral transport to seepage faces. These findings were validated using advanced HGS simulations, demonstrating the possibilities of integrating isotopic data to reduce uncertainty in hydrological models.
By addressing these complex interactions, the study contributes to improving the reliability of models used in soil water management, erosion control, and landslide risk assessment. The insights gained underscore the critical role of soil properties and preferential flow in shaping hillslope hydrology under varying environmental conditions.
“The physics-based model HGS was selected to resolve the interrelated flow equations in both the surface and subsurface domains, and the advection dispersion equations for the coupled solute transport process.”
Abstract:
Soil water movement plays vital roles in hillslope runoff generation and groundwater and surface water interaction. However, there are still knowledge gaps about the impacts of soil heterogeneity and preferential flow on the internal water flow and transport process. In this study, the vertical soil heterogeneity focused on the variations in soil retention capacity, and the consideration of lateral preferential flow emphasized the higher hydraulic conductivity. We combined isotopic tracing and numerical modeling in an artificial hillslope, focusing on monitored processes of the artificial rainfall and isotopic tracing experiment. The results showed that the soil moisture quickly accumulated at the bottom of the hillslope during rainfall events, while the 2H enrichment occurred in the topsoil derived from enriched isotope injection in the second artificial rainfall. The evaporation process slowed down the mixing of new water in the topsoil and old water in the lower layer. We found that the vertical soil heterogeneity had significant influences on the internal water and isotope transport paths within the hillslope. The lateral preferential flow played an important role in the water flux and transport time to the seepage face. The coupling of isotopic tracing, which reflects the water transport and mixing with the hillslope, effectively improved the model simulation and mechanism analysis of hillslope water flow. Our findings provide new insights into the mechanisms governing soil water flow and transport dynamics in hillslopes, taking into account vertical soil heterogeneity and lateral preferential flow.