EXERCISE 6: Execute a Transient Model of the Pumping

1. Copy ex5.gwv to exer\ex6\ex6.gwv

assign a root name of extr6
save files and save project as C:\temp\modflow\exer\ex6\ex6.gwv
be sure to correct the path to files and the name of the output files when you import results
2. Modify the BAS file: (initial heads, stress periods & timesteps need to be defined)

At first, we will use 1 stress period of 10 days with 20 steps increasing at a factor of 1.1

Note on page 4-12 of the MODFLOW manual or page 17 of the MODFLOW96 manual, an equation is given relating the size of the first step to the period length, the number of steps and the multiplier

Model>MODFLOW>Basic Package

turn off steady state

check time unit is seconds

Model>MODFLOW>StressPeriodSetup

period 1= 864,000 seconds, 20 steps, multiplier 1.1

What is the size of your first time step? answer

Model>MODFLOW>Initial Heads

Choose to read binary heads directly from the binary file

We would like to insert path to ex4b.shd, but that binary file was not created with GWV, so instead make another copy of the ex5 problem in the ex5 directory (you can do this in GWV by opening ex5.gwv changing Modflow>Packages root file names as ex5start, and saving it as ex5start, note you can have a number of gwv models open at once), but save this one as c:\temp\modflow\exer\ex5\ex5start.gwv with root file name of exstart5, then remove the well in both layers 1 and 3 and run the steady state without pumping to create the initial heads

returning to GWV ex6, insert ex5start.hds as starting heads

3. Modify the Storage Parameters / BCF file: add S1 & S3, for layers 1 and 3 as S1 = 1.3x10-3/50m and S3 = 2x10-4/50m; give S2 for layer 2 an extremely low storage as it was not consider at all in the initial model, say S2 = 1x10-12

Remember you need to be in property mode, set values in the data base, add color as desired, then set zone numbers

My first run after doing this failed. I searched text files and finally determined the dis file still hels SS instead of TR on each stress period definition. I was able to continue by editing the file before running the code. Then I found the option Model>>MODFLOW2000>>StressPeriodTypes and set them all to transient which fixed the problem. You should do this step now.
4. Packages that represent other stresses need not be changed because we still have only one stress period

5. Modify the Output Control

Model>MODFLOW>Output Control
Arrange to save for all time steps

Print as much as possible to the output file for checking purposes
Models>MODFLOW>OutputControl
uncheck the Disable printing box
Models>MODFLOW>PrintFormats
print all relevant items for your problem
6. Execute MODFLOW

Create MODFLOW files

View the new dis, bas, lpf, and oc files in a text editor

Execute MODFLOW and View results, perusing the MODFLOW output file, looking for conditions that you do not expect

As necessary, make corrections until you have a functional model

NOTICE the heads, drawdowns, flow rates and changes in flow rates due to the pumping as a function of time

NOTICE that near the end of the Plot menu there is an option for importing results

Import results for the first time step and make a profile along row 9

Repeat for the 20th time step

Compare the profiles with each other and with the pre-pumping and the steady state pumping conditions

Initial conditions:

First time step (0.17 days):

20th time step (10 days):

Steady state pumping:

GO "BACK" to continue the transient exercise