Review of saturated groundwater model codes for Hydro-JULES

This report reviews saturated groundwater model codes, one to be implemented into the Hydro-JULES modelling framework. First, the criteria for the code evaluation is described, and then commercial groundwater modelling codes, codes for thermo-hydro-chemical modelling and finally open source groundwater modelling codes are evaluated using the aforementioned criteria. Considering a groundwater code for the simulation of groundwater flooding or drought, we recommend either MODFLOW-2005, or the newly developed MODFLOW 6, the latter will need to be tested. Alternatively, BGS could develop a custom code that can solve the groundwater flow equation using moving grids, allowing a dynamic representation of the model grid for a moving water table. If also thermo and chemical processes are of interest, then codes such as OpenGeoSys, Dumux, and PFLOTRAN could be good choices, however they will need benchmarking to evaluate their ease of use