HW#4 - Introduction to MODFLOW

Note: You may work in pairs on this assignment.

1. Complete tutorial

a. Go to the Tutorials section of the Aquaveo GMS Learning Center:


b. In the General section, click on the PDF link associated with Grid Approach tutorial. Note: You don't need to download the associated zip file in this case.

c. Launch GMS and follow the steps in the tutorial to build a three-layer MODFLOW model in GMS.

2. Model Analysis

Using the things you have learned from the tutorial exercise, perform the following model analysis.

a. Using the flow budget tool, determine how much water is being lost through the drains.

b. Convert the number from the previous step to AFA (acre-ft per year).

c. Suppose that it is observed in the field that the actual discharge through the drains is approximately 100,000 m^3/day. Modify the conductance of the drain cells and rerun the model repeatedly until the discharge to the drains is equal to this value (+/- 2000 m^3/d). What is the resulting conductance?

d. Based on the conductance you found, would you say that the model is sensitive or insensitive to the drain conductance?

e. Did your changes cause the water level in the region surrounding the drains to go up or down? Does that make sense? Explain why it went up or down.

Submittal Instructions

Create an empty Word document. Make a screen shot of your grid to show that you completed part 1 and paste it into the document. Then enter your answers for part 2 (model analysis) in the document below the screen shot.

Upload your document via Learning Suite.