Visualizing Residuals

One way of assessing the quality of model calibration is to look at the residuals - the difference between an observed value and a simulated value generated by the model. Ideally, the residuals should be small and should not exhibit any obvious trends. ModelMuse can display the weighted residuals on the top view of the model using the PEST Observation Results pane of the Data Visualization dialog box. To display the residuals, the user selects the residuals file (.res) generated by PEST and clicks the Apply button in the Data Visualization dialog box. ModelMuse reads the file and displays its data in a table sorted by the absolute value of the residual. The weighted residuals are plotted as circles on the top view of the model. The area of the circles varies with the absolute value of the weighted residual and the color of the circle represents the sign of the weighted residual as calculated observed minus simulated.

Only some types of residuals can be plotted spatially as described above. The spatial plot includes only those residuals that are related to a single object that has a single vertex so that there is a unique location of the residual.

In addition to the spatial plot, the PEST Observation Results pane generates a graph of the weighted residual versus the observed value. This graph includes all the data from the residuals file including residuals for prior information equations.