The capability of iMOD to rapidly view and edit model inputs is essential to build effective models in reasonable timeframes. The rapid and integrated views of the geologic / hydrostratigraphic models as well as dynamic model output is critical for the public, stakeholders and regulators to understand and trust the model as a valid decision support tool. iMOD is fast even when working from very large data files because it uses a random accessible data format for 2D grids which facilitates instant visualization or editing subsets of such a large grid file. Also iMOD contains very economic zoom-extent-dependent visualization techniques that allow subsets of grids being visualized instantaneously both in 2D and 3D. Another feature is that iMOD generates MODFLOW input direct in memory, skipping the time-consuming production of standard MODFLOW input files (generating standard MODFLOW input files in ASCII format for large transient models may take hours to a full working day); this efficiency is especially useful during the model building phase when checking newly processed or imported data.
iMOD includes the MetaSWAP-module developed by Wageningen Environmental Research (Alterra); for references to the separate MetaSWAP-documentation see section A.2.8.
iMOD includes the functionality to perform calculations for density-dependent flow and reactive transport. This functionality comes as a stand-alone feature. More specifically, density-dependent flow and reactive transport calculations are performed with a separate executable called iMOD-WQ (iMOD-WaterQuality). iMOD-WQ is a combination of three codes:
• Seawat v4: the USGS code for density-dependent flow and transport ([Langevin et al.(2008)]);
• MT3DMS v5.3: the University of Alabama code for 3D multispecies reactive transport ([Zheng and Wang(1999), Zheng(2010)]);
• RT3D v2.5: the Pacific Northwest National Laboratory code for 3D multispecies reactive transport for more complex reactions ([Clement(1997), Clement and Johnson(2003)]).