RmaMf2005: Next Steps

The goal of this model is to understand the risk posed by the contaminants in the flow from the disposal pond to the water supply wells. To further evaluate this risk, we might want to use MODPATH or even run a solute transport simulation. MODPATH and solute transport simulations are covered in some of the other examples such as the original Rocky Mountain Arsenal example on which this example is based. At present, ModelMuse does not support using PEST with MODPATH or solute transport models.

We looked at how well the model matched the true hydraulic conductivity and pumping rates. That isn’t something we could do in a model of a real groundwater system. We also used a very low value of PHIMLIM, the target measurement objective function. To avoid overfitting the model, our next step would be to run PEST again but with PHIMLIM and PHIMACCEPT set to larger values. Anderson and other (2015, p 418) suggest a value 10% higher than in the best fit value recorded in the PEST run record. PHIMACCEPT is typically 5-10% larger than PHIMLIM.

PEST comes with a variety of utility programs for a variety of purposes such as statistical postprocessing utilities used to gain a better understanding of the information content of the calibration dataset, and of the estimability of individual parameters. Other utility programs are used for exploring the uncertainty of predictions made by the model.

ModelMuse was not designed to support PEST++ (White and others, 2020) directly. Nevertheless, PEST++ was designed to be backwards compatible with PEST so it should be possible to use PEST control files generated with ModelMuse with PEST++. If the user wishes to use capabilities of PEST++ that are not included in PEST, that can be done by appropriately altering the PEST control file.