Introducing APEXMOD - A QGIS plugin for developing coupled surface-subsurface hydrologic modeling framework of APEX, MODFLOW, and RT3D-Salt

This article presents APEXMOD, an open-source QGIS plugin that helps add a MODFLOW grid to the APEX watershed model. The APEX model integrates MODFLOW, a physically based groundwater model and RT3D-Salt, a groundwater nutrient and salt transport model, for basin-scale application as a coupled surface-subsurface hydrologic modeling system. APEXMOD is developed as a tool that enables the dynamic linkage between APEX, MODFLOW, and RT3D-Salt. APEXMOD is written in Python and integrates QGIS geoprocessors and spatial packages. The APEXMOD interface is constructed with three modules: (i) a pre-processor that prepares inputs for MODFLOW and RT3D-Salt and performs spatial linkage between APEX subareas and MODFLOW grid cells, (ii) a model configurator that controls simulation options and scenario setting, and (iii) a post-processor for visualizing and analyzing model outputs. A case study was conducted in the Animas River watershed to demonstrate the core capabilities of APEXMOD. •A new open-source software called APEXMOD was developed on the QGIS platform.•The software facilitates the linkage of APEX, MODFLOW, and RT3D-Salt models (AMRS).•A case study utilizing the software performed the AMRS simulation successfully.