HydroModPy: A Python toolbox for deploying catchment-scale shallow groundwater models 

Abstract. In response to the growing demand for groundwater flow models, we present HydroModPy, an open-source toolbox designed to automate their deployment at the catchment scale. Built on top of the MODFLOW-enabling FloPy library, HydroModPy combines the robust WhiteboxTools toolbox for geospatial analysis and the well-validated MODFLOW code for groundwater modeling. This Python-based toolbox streamlines the construction, calibration, and analysis of unconfined aquifer models while adhering to FAIR (Findable, Accessible, Interoperable, and Reusable) principles. It enhances model reproducibility through editable Python code, supports multi-site deployment, and provides compatibility with alternative groundwater flow solvers. Furthermore, it integrates pre- and post-processing functionalities to simplify workflows. The toolbox enables catchment delineation and hydrological feature extraction from DEMs, followed by semi-automatic model construction and advanced visualization of hydraulic head and flow results. Users can choose from predefined aquifer structures and hydraulic properties such as exponential decay of hydraulic conductivity and porosity with depth or import complex 3D geological models. HydroModPy outputs can be exported in standard formats (e.g., raster, shapefile, netCDF), including water table elevation, water table depth, groundwater storage, groundwater-dependent hydrographic network and streamflow rates, and subsurface residence times. HydroModPy is tailored for the deployment in diverse geomorphological and hydrological settings, enabling the testing and exploration of aquifer models under varying recharge conditions. Its deployment capabilities are demonstrated in complex shallow basement and crystalline aquifers, where topography and geology primarily govern groundwater flow dynamics from hillslope to catchment scales. As an open-source toolbox, HydroModPy is designed for the community and actively encourages contributions from its users. It supports research in hydro(geo)logy and land and water management, while also providing valuable opportunities for teaching and education.