Reproducible construction of a high-resolution national variable-density groundwater salinity model for the Netherlands

Freshwater availability in the coastal zone is threatened by overexploitation, seawater intrusion and global change. Recent advances in parallel computing of coupled variable-density groundwater flow and salt transport models enable the construction of large-scale high-resolution models, key to support sound policy making. Here, we present the construction of a nationwide coupled variable-density groundwater flow and salt transport model for the Netherlands, derived from the existing nationwide groundwater flow model. Construction of the model is fully scripted in a reproducible and transparent version-controlled workflow, aiding regular updating and stakeholder trust in model results. A 3D groundwater salinity distribution was interpolated from over 2M available measurements using Multiple Indicator Kriging as a starting condition in the model. Calculation of a high-end sea-level rise scenario shows the added benefit of large-scale groundwater salinity modelling for policy making. The presented approach is generally applicable to groundwater flow models of coastal aquifers.