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20. (13 pts) The following model has been constructed for the Elk River site:

Our objective is to parameterize the model input and calibrate the model using PEST.

Click here to download a zip archive containg the GMS project file for this model.

**Click here to download a copy of the solution.**

Unzip the archive, open the project in GMS and do the following:

a. (3 pts) Go to the *Project Explorer* window and review the coverages associated with the conceptual model. Note that it is a two-layer model with a separate coverage for the hydraulic conductivity in each layer. Parameterize the model input associated both the K and recharge polygons using key values as shown in the following figures:

b. (1 pt) Use **Map->MODFLOW** to copy the key values to the MODFLOW grid.

c. (2 pt) Change the model to parameter estimation mode.

d. (3 pts) Go to the parameters dialog and set up your parameters. Enter the starting values shown in the figure above for recharge and K. Note that the parameters may not be listed in order.

e. (3 pt) Turn on the **Solve** option for all parameters **except** HK_600 and RCH_1000. You will be solving for a total of nine parameters. Turn on the **Log Xform** option for the HK parameters.

f. (1 pts) Go into the Parameter Estimation options dialog and change the max number of iterations (NOPTS) to 6. This will ensure that your model doesn't take forever to run.

f. (2 pt) Save your model as **erinverse.gpr** and solve using PEST.

(Upload instructions and links went here)