There are 2 repositories under groundwater-flow topic.
GroundWater Spatiotemporal Data Analysis Tool (GWSDAT) R-Shiny implementation.
Groundwater flow and steady-state advection-diffusion solver for OpenFOAM (C++), based on the porousMultiphaseFoam solver.
Scripts for a manuscript titled "Subsurface Microbial Communities Reflect Regional-Scale Groundwater Hydraulic Connectivity" (submitted)
Phase-averaged tidal boundary condition for numerical groundwater flow models in flopy with MODFLOW-2005, SEAWAT, and MODFLOW 6