CE En 547 - Midterm Exam #2 KEY

Fall Semester 2017

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Essay Questions

Click here to access the Equation Sheet.

14. (4 pts) (calibration) What is the benefit of copying the computed heads from a successful forward run with MODFLOW to the starting heads array prior to performing an inverse run?

15. (4 pts) (calibration) Suppose that after calibrating a MODFLOW model using PEST, you open up the *.MTT file generated by PEST and you see the following at the bottom:

Eigenvalues ----->
3.8272E-02 8.2882E-07 7.0928E-12 3.7482E-05 1.8478E-04 9.2823E-09

Is your model unique or non-unique? Justify your answer.

16. (4 pts) (calibration) Why is that we should not expect to achieve a perfect fit between field-observed and model-simulated values when calibrating MODFLOW models? How does one go about determining when a model is sufficiently calibrated?

17. (4 pts) (calibration) What is the point of using arc groups when calibrating a MODFLOW model using GMS? Why not just assign the observed discharge to individual arcs?

18. (4 pts) (calibration) Describe some advantages and disadvantages of using the pilot point method for model parameterization (vs. zonation).