GW Vistas Tutorial (Developed by Dr. Clement’s group at ...clemept/GW_modflow_lectures/tutorials... · GW Vistas Tutorial (Developed by Dr. Clement’s group at Auburn University

GW Vistas Tutorial (Developed by Dr. Clement’s group at Auburn University ([email protected])

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Register and get GW vistas from here: http://www.groundwater-vistas.com/index.html http://www.eng.auburn.edu/~clemept/cvl6150.html MODFLOW

In case 1 we will use MODFLOW to develop a steady state groundwater model with a 100 m

boundary condition on the left side and an 80 m boundary condition on the right side. Once

the model reaches steady state, we should see a sloping head distribution based on the

boundary conditions.

Case 1. : Steady State without recharge

1. Select File ->New from the main menu or click the new document button.

2. Basic information

Number of rows 50

Number of Columns 50

X spacing 20 m

Y spacing 20 m

Number of Layers 1

Bottom Elevation 0

Top Elevation 120 m

Number of Stress period 1

Kx, Ky, Kz 0.5 m/day

3. Mode->MODFLOW->Package

Change the root file name to prob1

4. Model->MODFLOW->Package Option

At Basic tab, let the Time unit : days , Length Unit : Meters

Click on the BCF-LPF tab. Make sure Layer 1 is type 1(unconfined)

5. BC->Constant Head

For left boundary condition, BC->Insert->Window

Select the left column of cell by pulling a box around

Constant head is set to 100 m

For right boundary condition, BC-Insert-Window

Select the right column of cell by pulling a box around

Constant head is set to 80m

6. Model ->Path to model

Change the directory

7. File->Save

Save the file name “prob1”

8. Run MODFLOW (Click the calculator button).

http://www.groundwater-vistas.com/index.html


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A message first asks if you want to create datasets. Choose YES.

9. Result dialog

When MODFLOW is finished, a dialog will be displayed notifying you that the simulation is done

and asks if you want to process the results. Choose YES to start the post-processing session.

At the dialog box (shown as Import Model Results), check the box next to Cell-by-Cell Flow so

that we can see the mass balance results. Click OK when you are done.

10. Plot->Mass Balance->Model summary

You can see flow budget and you should see about 900 m3/day of flow of inflow and outflow.

Verify this number analytically. Note q* =k/2L (h22-h1

2) is the flow/unit-width per day.

You need to multiply by 1000 to get the total flow. Note we assumed 1000 m as the width of

this problem domain.

You can see a similar water budget information from Model summary.

Questions 1. What is the GW level at x = 700 when there is no recharge? Answer : close to 86.5 m

You verify this by looking at the contours or click on any cell and in the bottom left of your screen you can see its x, y, and z coordinates and the exact value of the head

2. Can you see the actual water table distribution? Select Plot->Profile->Head


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Figure 1. The head distribution with two constant boundary conditions

In this case, we will add recharge into the model created in case 1 to observe the mounding of

the water table due to the additional input. The results from this model will later be used as

the initial head inputs for the transient model.

Case 2 Steady State with recharge

1. MODFLOW ->Package

Change root file name to prob1R

2. Property -> recharge

3. Property ->property value -> Database

Set value 0.00323 (is equal to 0.00323 m3/m2-day)

4. File->Save As Save the file name “prob1R”

5. Run

Questions Verify maximum head and its location (101.6m, 221.4 m from river)


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Use mass balance (go to Plot-Mass balance-Window) to compute in and out flow and check against analytical calculations ; Note with recharge q* =k/2L (h2

2-h12)-N(L/2-x)

Hand calculate flow at a couple of x locations and check it against the model results given below: for Column 29 In : Recharge : 64.6 m3/day Left face : 1112 m3/day Out Right face : 1177 m3/day Similarly for Column 43 In : Recharge : 64.6 m3/day Left face : 2016 m3/day Out Right face : 2080 m3/day

Figure 2. The head distribution with recharge condition.

Obs: Flow is not constant due to Recharge.


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Mass Balance for the entire system:

Water leaving the system from left boundary condition : 632 m3/day Water leaving the system from right boundary condition : 2,469 m3/day Water getting into the system(recharge ) : 3,100 m3/day Note you can compute the total recharge into the system analytically, which approximately = 0.0032*1000*1000 (m/day*m*m)

In this case, we will take the model developed in case 2 and add in a pumping well. Due to the

pumping, we should observe contour lines in the flow field representing drawdown from the

well.

Case 3 : Steady State with pumping and recharge

1. MODFLOW ->Package

Change root file name to “prob1W”

2. Select BC ->Well

3. BC ->Insert ->Single Cell

4. Move the cursor to Row 25 column 40 and click the left button

Enter a flow rate of -2000 m3/day (note negative sign is used to denote extraction well)

5. Go to File ->save as “prob1W”, now a new MODFLOW dataset with the well package will be

saved.

6. Run

7. Result dialog

8. Read solutions (Figure 3)

Read the solution and you should see nice round contours near the well and also see that the

well effects are affecting the boundary and the well is directly getting water from the boundary

Question 1. What portion of the well flow is coming from the aquifer and from the river

located on the right-hand boundary?


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Open the Mass Balance-> model summary window. You will see inflow from constant head as 99.7 m3/day (which is the water supplied from the river to the aquifer), rest of the well flow is the portion of the recharge captured by the river (which is equal to 2000-99.7=1900); Note the remaining recharge is flowing into the river.

Figure 3. The head distribution in the existence of a well.


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This case leads the student through the process of developing a transient model. The model

will be similar to case 3, in that it contains recharge and pumping, but it will be transient. The

student will have to use the head values from case 2 as the initial heads in this case. Since the

model will be transient, we will be able to flip through the results at each time step.

Case 4 Transient with pumping and recharge

1. MODFLOW ->MODFLOW ->Package

Change root file name to prob1trans

2. Prop -> Storage/Porosity Change the storage value to 0.1

3. Model ->MODFLOW ->Package Option

Uncheck the option labled Steady-State Simulation.

4. Model ->MODFLOW ->Stress period data

Period Length : 100 days (Our simulation time)

Number of time steps : 10 (What does time step stand for?)

5. Model ->MODFLOW2000 ->stress Period Types ->Edit Stress Period Types.

Set the type as 1 (transient)

6. BCs ->Well

Move the cursor over the wells and double-click the left mouse button.

Turn off the flag that says “Steady-State boundary” and click the transient data button.

Enter a 1 for the starting and ending stress period.

Enter -2000 for the pumping rate.

7. Initial condition : We will consider as an initial water table, the final head distribution

from the previous case 2(steady state with recharge). Since We are dealing with a

transient problem, accurate description of the initial condition is required. Note to solve

transient problems you need both initial and boundary conditions. To do this you need

“prob1R” solution in the memory.

Select Model ->MODFLOW ->Package Options and click on the initial heads Tab.

Change the option at the top to set heads from headsave, BASIC, Surfer, Matrix

Click the Browse button and find the prob1R.hds.

8. GWV allows you to monitor head, drawdown and concentration over time during a

transient simulation.


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Analytical Element->Well. Move the cursor to pumping well and click the left mouse

button. Change the pumping rate to 0.0 and place a check mark next to Monitor

Head/Concentration vs. Time.

Click the Name button and enter MW-1 for the mane of this monitoring well. Click OK.

9. File ->Save as “prob1trans”

10. Run

11. Result dialog

12. Read Solution (Fig. 4)

13. Plot-> Hydrograph-> Monitoring Well. A dialog will show all of the observation well.

Figure 4. The head distribution at the transient state time step 1 (3.85 day)

Question 1 :

Have we reached steady state? Solution : Flip through the solutions at various times and visually see

whether it has reached steady state.

Another more rigorous way to do this is to check the flow budget and see whether the contribution

from storage has reduced to zero. Note at steady-state in and outflow from boundaries will be balance

and change in storage will be zero.

Go to Plot –>Mass balance –>Model Summary

Or Model->MODFLOW –>View Output File


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As we can see, water coming from storage is quite high for this problem. This implies that the system is

not at steady state. In steady state the value of storage should be close to zero.

Question 2:

What are sources of pumped water?

Note when we solved the steady state problem part of the pumped water was the recharge flux and

part was from the downstream river boundary. Now under transient condition, we have an additional

contribution from the aquifer storage (for unconfined flow the pores will actually drain and contribute

through the specific yield term).


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Steady state (data from case -2)

In: Recharge : 3,100 m3/day

Out : Discharge into constant head boundaries : 3,100 m3/day

(2,469 m3/day to the right, 632 m3/day to the left)

Transient State (see above mass balance for the last time step from 90 day to 100 days)

In: Recharge : 3,100 m3/day

From storage 1,004 m3/day (get it from budget file)

Out : Constant Head Left 602 m3/day

(get it by selecting plot->mass balance->window)

Constant head (right) 1,503 m3/day

(get it by selecting plot->mass balance->window)

Well : 2,000 m3/day

Total out =4,105 m3/day

Note, under steady state condition 2,469 m3/day of water came from right BC but under transient

condition between 90 and 100 days on average only 1503 m3/day of water is coming from right BC :

Reduction right BC : 2,469-1503 = 966 m3/day

Similarly reduction Left BC : 632-602 = 30 m3/day


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MT3D

This case will introduce the student to using MT3D to model contaminant transport. Using the

transient file created in the last case, we will insert a contaminant plume and then pump. Due

to the pumping we will see the migration of the contaminant plume towards the pumping well.

Case 1 Contaminant transport

1. File->Open

Select prob 1trans. Gwv.file

2. Props -> Recharge

Prop-> property values -> Database

Enter a recharge rate of 0.00323 in zone 2 and a concentration of 1000.0.

Change the color to a nice red(or green)!

3. Props-> Set value or Zone numbers -> Windows

Drag a window on the left-middle of model .

Make this window area zone 2.

4. Model ->MODFLOW ->Package

Change root file name prob5

Place a check mark next to Mt3D Flow Output at the bottom of the dialog

5. Model ->MODFLOW ->Stress period data

Period Length : 1000 days (Our simulation time)

Number of time steps : 10

6. File ->Save as “prob5”

7. Run

8. Model ->MT3D->Package

Change root file name prob5

Place a check mark next to Mt3D Flow Output at the bottom of the dialog

Make sure the version is MT3DMS at the bottom of the dialog.

Turn on the GCG solver package and turn off reactions.

9. Model ->MT3D->General Option

click on the Advection tab. Make sure this is set to Finite Difference.

Next, click on the Printing tab. Place a check mark next to the item labeled Save

Concentration in Binary File. Change the frequency of output to Every N Time Steps and

the number to 2.

Click on the Time Stepping tab. Confirm that the initial time step size is 0.1 with a

maximum step size of 500 days and a multiplier of 1.2 (Default).


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10. Model ->Use MT3D

11. Run

If MT3D does not run, select Model->Path to Models and confirm that the MT3D model

is MT3DWIN32.dll.

12. Result dialog

Click the Browse button next to the transport time step.

Choose the last time step at 1,000 days (should be step number 33).

Check boxes of concentration file and cell-by-cell flow.

Click OK and GV will read heads and concentrations.

13. Plot->What to Display

Change the variable to contour from Head to Concentration.

Figure 5. The concentration distribution at 1000 days.


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SEAWAT

This tutorial will introduce the student to the concepts of SEAWAT. We will simulate the Henry

problem, in which there is a saltwater constant head boundary on the right side of the flow

field and a freshwater flux on the left side. If the model simulates the situation correctly, we

will see a saltwater wedge form after time, with the interface between the freshwater and

saltwater clearly displayed.

Case 1- Henry Problem

This tutorial is adapted from the SEAWAT training course given by Langevin, Guo, and Dausman

1. Click File New

2. When the input box pops up, set the following parameters:

# of Columns: 21

# of Rows: 1

X-Spacing: 0.1 meter

Y-Spacing: 1 meter

# of Layers: 10 (if you are running the Student Version you will only be able to use 4 layers)

Bottom Elevation: 0

Top Elevation: 1

Kx, Ky, Kz: 864 m/day

Porosity: 0.35

Storage: 0.0001

*the units for the simulation will be set in a later step, for now just enter the numbers with the

understanding of what the units are.

3. Click OK


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4. Go to Models Path to Models choose directory for your work files to be put in.

5. File Save As Choose name and save file

6. To mimic the ocean we will insert a constant head boundary along one side of the grid.

Click BCsConstant Head

Click BCs Insert Window drag the window in the cell at the right hand side of the model in the plan

view (column 21)

When the first window pops-up click Ok.

When the second window pops up enter the head at the Boundary as 1 m, concentration as 35 kg/m^3,

and confirm that constant head box is checked (if not, check it now). Do NOT check the constant

concentration box.

Un-click the Steady State box. Click the Transient Data Box. This should prompt another screen to pop-

up. Enter 1 for Starting Stress Period, 1 for Ending Stress Period, 1 for Head Value, and 35 for

Concentration. Click OK and then OK again.

7. To copy this BC to the rest of the layers follow these steps:

Go to layer 2 using the + button for Layers to the left of the grid.

Once in layer 2 click BCs Copy.

When the dialog box pops up the layer to copy from should be 1 and you should copy all reaches.

Change copy BC’s to layer: 2 to Layer 10. Click OK.

8. Now the column width of column 21 must be changed to match the Henry Problem parameters. To

do this:

Click GridEditColumn Spacings. Go down to 21 and change width to 0.01. Click OK. If this was

done correctly, column 21 should now appear narrower on the screen.

9. Now we will set the initial concentration to the value of seawater:

Click Props Initial Concentration PropsDatabase

In Row 1, column 1 enter the value 35. Click OK.

10. We will now insert a well into the left hand column to simulate a flux:

Click BCs Well BCsInsert Single CellClick in the cell in Layer 1, Column 1. Enter 0.5702 (If only

using 4 layers use 1.4255) for Qin for the well.


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Click OK.

Go to Layer 2 and click BCsCopy and use the same protocol that was used in Step 7 above. Click OK.

11. Click Model MODFLOW Stress Period Setup. Change Period Length to 2, Number of time

steps to 1 and Time Step Multiplier to 1.

12. Click Model MODFLOW2000 Stress Period Types Set all to Transient

13. Click ModelMODFLOW Packages

Make sure PCG2 solver is selected (this stands for Preconditioned Conjugate Gradient Solver)

Change the MODFLOW version to SEAWAT2000

Change the root file name to henry

Underneath the Package Option click to box to create the CHD package (stands for Time Variant

Constant Head Package) and change the unit to 20. Click OK

14. Click ModelMODFLOWPackage Options. Click the Output Control Tab. Click the box next to

Always Save data at the last time step of the run.

Go to the GCF-LPF tab, and push the button labeled all layers confined.

Go to the Density tab and enter 0.025 next to increase in Density at Max Concentrations. Enter 35 next

to Maximum Brine Conc. Make sure that the Correct Boundaries for Density box is not clicked. Click

OK.

15. Click MODEL MT3D/RT3DGeneral Options

Click the Advection tab. Select the solution Scheme Finite Difference. Set the Maximum Total Particles

to 500000 and weighting to upstream.

Click the Basic Transport Tab. Set the time units to DAY, Length units to M and weight units to KG.

Click the Time Stepping Tab. Set the initial transport time step to 0.0001 day, change the Maximum

transport steps per flow step to 99999 and put in a Timestep multiplier of 1.5. Change the maximum

time step size to 0.

Click the Printing Tab and next to the frequency of output, set it to every N time steps and print every 1

time step.

Click the GCG solver tab. Change the solver option to SSOR. Click the box to include full dispersion

tensor.


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Click OK.

16. Model MT3D/RT3DPackages. Set the root file name to henry.

17. We will now set the SEAWAT options so that the variable density flow will be simulated.

Click Model SEAWATOptions.

Set the fractional increase between Seawater and Freshwater to 0.025.

Set the Concentration of Pure Seawater to 35.

Change the Maximum Number of coupling iterations (NSWTCPL) to 1.

Click OK

18. Click Model SEAWAT SEAWAT2000 VDF Package Options

Change MTDNCONC to 1-species 1 coupled flow and transport.

Set DENSEMIN and DENSEMAX to 0.

Set the Reference Fluid Density (DENSEREF) to 1000, which is the density of freshwater.

Set the Density-Concentration Slope (DENSESLP) to 0.714, which is the change in density between fresh

and seawater divided by the change in concentration of fresh and seawater.

Set FIRSTDT to 0.01.

19. Now we will run Seawat but first we need to create the SEAWAT datasets.

Click Model SEAWAT Create SEAWAT datasets

When the two dialog boxes pops up, you can click OK to view the warning files if you want, if not click

cancel.

20. Now we will import the results from the SEAWAT run

Click PlotImport Results.


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When the window pops up to import results, browse for the head file henry.hds and the concentration

file MT3D001.ucn and click the boxes so that both of these files are imported.

Next to transport time step, browse and click on transport step 23. Click OK.

Click OK and the data should now import into Vistas.

21. Now we will view the results that were just imported:

Click Plot What to Display

Go to Display Contours of and set it to Head

Go to Display Color Flood of and set it to Concentration

Click OK

If the model has run correctly you should see a saltwater interface with the ocean on the right hand side

and fresh water above it on the left hand side of the grid.

To check the mass balance for the simulation:

Click PlotMass Balance and then select an option. This should show you how much groundwater is

discharging into the Ocean.


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MODFLOW TUTORIAL From Numerical Methods Class Problem

This tutorial solves the groundwater problem under the same circumstances that it was solved for Dr.

Clement’s Numerical Methods class using 2-D Well Code.

In case 1 we will develop a very similar steady state situation as developed in Case 1 of the MODFLOW

section except some of the parameters will be different.

Case 1: Steady State (without pumping)

1. Click File New from main menu or click the New document button

2. Change or confirm the following information:

Number of Rows 50

Number of Columns 50

X Spacing 20 m

Y Spacing 20 m

Number of Layers 1

Bottom Elevation 0

Top Elevation 100

# of Stress Periods 1


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Kx, Ky, Kz 1, 1, 0.1 m/day (respectively)

S value 0.00001

3. Model MODFLOW Package

Change the root file name to prob1

4. Model MODFLOW Package Options

Go to Basic Tab, change the time and length units to Days and Meters

Go to BCF-LPF tab. Confirm that Layer 1 is type 1 (Unconfined)

5. BC Constant Head

To make left hand BC: BC Insert Window

Drag the window box inside left column from top to bottom and then let go

Set Constant Head to 150 m in the dialog box that will pop-up

To make right hand BC: BC Insert Window

Drag the window box inside right column from top to bottom and then let go

Set Constant Head to 149 m in the dialog box that will pop-up

6. Model Path to Model

Change the working directory to the folder that you would like the files created by MODFLOW to be

stored

7. File Save

Save the file with the name: prob1

8. Click the calculator button to run MODFLOW

When asked if you want to create datasets, click YES. Click Yes to see error file.

9. Results Dialog

When asked if you want to process the results, choose YES. Once the dialog box shows up (called Import

Model Results) check the box next to Cell-by-Cell Flow so that the mass balance results are displayed


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Click OK

10. Plot Profile Head

The plot should look something like this:

11. PlotMass BalanceModel Summary

Inspect the Mass Balance to make sure that the flow budget makes sense


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In Case 2 we will use the model created in Case 1 but add in a pumping well.

Case 2: Steady State with Well (Using Saved File from Previous Simulation)

1. MODFLOW Package

Change root file name to prob1W

2. BC Well

BCInsertSingle Cell

Move cursor to Column 25, Row 25 (numbers are displayed along bottom of the window) and click the

left button

3. Enter flow rate of -1000 m3/day (negative is used since water is being withdrawn)

4. File Save As Save as prob1W

5. Run (same way as last simulation)

7. Results Dialog will come up, go through same process as before

8. Read solutions and plot various properties to observe steady state drawdown and check mass

balance.


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In Case 3 we will develop a transient simulation with well pumping, very similar to the one developed in

Case 4 of the MODFLOW section.

Case 3: Transient with Well

1. ModelMODFLOW Package

Change root file name to prob1trans

2. Model MODFLOW Package option

Uncheck the option Steady State Simulation

3. Model MODFLOW Stress Period Data

Period Length: 100 days

Number of Time Steps: 10

4. Model MODFLOW2000Stress Period Types Edit Stress Period Types

Set the type as 1 (transient)

5. BCs Well

Move the cursor over the well and double click the left mouse button

Turn off the flag that says Steady State boundary and click the transient data button

Enter 1 for the starting and ending Stress Period

Enter -1000 for the pumping rate

6. Model MODFLOW Package Options

Click the Initial Heads Tab

Change the option at the top to set heads to headsave, BASIC, Surfer, Matrix


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Click the Browse button and find the prob1.hds and select this file

(This step is necessary since we are dealing with a transient simulation. For transient simulations,

accurate description of the initial condition is required.)

7. AE Well

Move the cursor to the pumping well we previously added and click the left mouse button (this places a

monitoring well right next to our pumping well). Change the pumping rate to 0 and place a check mark

next to Monitor Head/Concentration vs. Time

Click the Name button and enter MW-1. Click OK

(This well will allow us to monitor head, drawdown, and concentration over time)

8. File Save As Save as prob1trans

9. Run (same way as for previous simulations)

10. Results Dialog

Since we used multiple time steps in this simulation, make sure to select the time step that you want to

import. In most cases this will be the last time step. In our case this will be time step 10.

11. Read solutions and plot various properties such as head at the column where the well is located (25)

to observe drawdown. The plot should look something like this at the final time step (TS 10):


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Also, plot the hydrograph from MW-1 so that you can see the Head vs. Time (This figure is for TS 10) The

head in this figure can vary if you place your monitoring well in a different location.

Documents

GW Vistas Tutorial (Developed by Dr. Clement’s group at ...clemept/GW_modflow_lectures/tutorials... · GW Vistas Tutorial (Developed by Dr. Clement’s group at Auburn University