This post highlights the time varying maximum timesteps command, which helps optimize simulation runtimes while maintaining high temporal resolution during periods of rapid model input changes. The time varying maximum timesteps command allows you to adjust timestep sizes dynamically using a simple time-value table. A sample problem demonstrating this feature, based on the "Abdul" verification model, is available for download. This version refines timesteps during key boundary condition changes, leading to approximately 100 additional timesteps and improved solution refinement.

This post describes how to use the minimum layer thickness and minimum layer thickness with fixed top elevation commands to enforce nodal elevation rules when building your model mesh or grid. These commands help prevent pinchouts, which occur when nodes in upper layers have lower elevations than those in layers beneath them—a common issue when working with large surface data files in complex geological systems.

This post describes how to use the zones from arcview for chosen elements command to define property zones using shapefile (.shp) data. This method is particularly useful for projects involving spatially distributed properties in both the porous media and surface domains.

This week, we're highlighting a newly added command: compute post simulation average. This command was designed to simplify coupling PEST (Parameter Estimation) with HydroGeoSphere (HGS) by extracting average values of simulated quantities over a specified time interval and storing them in a file that PEST can easily read.

This post highlights three grok utility commands that are useful for building and debugging your grok file. These commands are particularly beneficial when you want to skip over certain sections of the code that aren’t necessary for execution during a specific run.

This post describes how unsaturated tables can be used to speed up model runs. Unsaturated tables refer to the Pressure-Saturation and Saturation-Relative Permeability tables that can be generated from van Genuchten parameters in an MPROPS file when running grok.exe. Conceptually, these tables replace the need for on-the-fly calculations of unsaturated properties during simulation, improving computational efficiency.

This post describes how to use two methods for setting initial head conditions from previous simulations. The first method, Initial head from output file, assigns an initial head value to all nodes in the current domain by reading it from a previously generated output file. This method is particularly useful when you want to avoid starting a simulation from scratch after a crash or when using results from a prior simulation to initialize a transient model. The second method, Restart file for heads, uses the prefixo.hen file, which contains the head for all nodes across all domains after a simulation’s successful completion. This allows the model to restart from the exact conditions saved in the file.