Development of a Computational Framework for Statewide Coupled Surface Water and Groundwater Modeling

New Mexico, one of the fastest-warming states in the United States, faces increasing challenges in managing water resources because of declining snowpack and intensified groundwater extraction. To address these challenges, we developed a high-resolution, fully automated hydrologic modeling framework that couples the Variable Infiltration Capacity (VIC) surface water model with the MODFLOW 6 (MF6) groundwater model. This coupled hydrologic modeling framework, called VIC-MF6, can be used to simulate surface-subsurface hydrologic interactions across New Mexico from 1940 to 2100 using observed and Coupled Model Intercomparison Project Phase 6 (CMIP6)-projected climate data at a 1/32° resolution. It includes modules for parameter downscaling, data conversion, and model synchronization via the MF6 Application Programming Interface (API) based on the eXtended Model Interface (XMI), allowing monthly exchange of baseflow and groundwater discharge. The model was applied to the domain of the Rio Grande Transboundary Integrated Hydrologic Model (RGTIHM), demonstrating scalability, computational efficiency, and physical consistency. Key findings highlight the seasonal dynamics of soil moisture and the long-term trends in groundwater drawdown. Software modifications improved VIC-MF6 compatibility and implemented critical features for MF6 to accommodate the RGTIHM’s geological structure within the coupled framework. This study presents the first tightly coupled, statewide hydrologic simulation framework for New Mexico, offering a robust tool for evaluating long-term water availability, drought vulnerability, and sustainable water resources management under variable climatic conditions.