The deep vadose zone serves as a critical interface connecting surface water processes and groundwater systems. Its water dynamics influence groundwater recharge, solute transport, and groundwater recovery. However, strong geological heterogeneity, long-term hydrological memory, and dynamic groundwater boundaries make regional-scale high-resolution simulations challenging.

Researchers from the Center for Agricultural Resources Research, Institute of Genetics and Developmental Biology, Chinese Academy of Sciences, led by Prof. Shiqin Wang, developed the Parallel Regional Infiltration and Solute Model (PRISM), a regional one-dimensional model for simulating water and solute transport in deep vadose zones. By integrating parallel computing, database-based data management, and dynamic groundwater boundary representation, PRISM enables long-term regional simulations of vadose-zone processes (Fig. 1). Using PRISM, the team reconstructed vadose-zone water dynamics for 15,671 spatial units in the plain area of the Baiyangdian Lake watershed from 1980 to 2024, revealing hydraulic regulation mechanisms under changing groundwater conditions (Fig. 2).

The results showed that increasing groundwater depth gradually shifts deep vadose-zone behavior from geological control toward dynamic water-state regulation. When groundwater depth exceeded approximately 11.9 m, surface hydrological signals were substantially attenuated before reaching groundwater. Meanwhile, historical moisture conditions maintained hydrological memory, allowing surface–groundwater connectivity to persist at approximately 15 m depth. The study further demonstrated that groundwater recovery does not necessarily restore vertical connectivity between surface infiltration and groundwater; instead, rising groundwater levels primarily modify lower-boundary conditions and reshape subsurface hydraulic states.

This study provides a new modeling framework for regional-scale deep vadose-zone simulations and offers a scientific basis for understanding groundwater responses under long-term environmental changes, evaluating groundwater recovery impacts, and assessing long-term risks associated with agricultural non-point source pollution. The study, entitled “A mechanism-data-driven framework reveals hydraulic decoupling transitions and hydrological memory under transient phreatic boundaries,” was published in Geoderma (2026, 474:118046). Zhixiong Zhang is the first author, and Prof. Shiqin Wang is the corresponding author. This work was supported by the National Key R&D Program of China (2021YFD1700500), the National Natural Science Foundation of China (No. 42377080), the Foundation for Innovative Research Groups of the Natural Science Foundation of Hebei Province (D2021503001), and the Hebei Provincial Science and Technology Program (262N3601D).

Full-text link

Zhixiong Zhang, Shiqin Wang, Wenzhao Feng, Zilong Zhang, Kangda Tan, Wenbo Zheng. A mechanism-data-driven framework reveals hydraulic decoupling transitions and hydrological memory under transient phreatic boundaries. Geoderma, 2026, 474: 118046. https://doi.org/10.1016/j.geoderma.2026.118046

Fig. 1. Parallel computing architecture of the PRISM model and physical simulation framework for the vadose zone.

Fig. 2. Hydraulic decoupling transitions, hydrological memory, and lower-boundary effects during groundwater recovery.