1. Groundwater Modeling Assignment #2

2. Parts A and B

3. Description Well pumping an unconfined aquifer at 18,000 m 3 /day. Will pumping “significantly reduce” the discharge to the wetland at south? Grid = 40 Rows, 18 Columns Grid cells = 250 m x 250 m All cells are 40 m thick Plan View N-S Cross-Section View

4. Create a New Model Start the GV program Select File --> New Enter basic information about the model – # rows = 40 # cols = 18 – Row spacing = 250 m – Column spacing = 250 m – Top of Layer 1 = 1020 m – Bottom of Layer 1 = 980 m

5. Model Grid 1020 m 980 m Layer 1 – K h = K x = K y = 50 m/day – K v = K z = 50 m/day Pumping – 18,000 m 3 /day Recharge – 0.001 m/day

6. River Boundary Conditions Select  Layer 1 Select BCs  River Select BCs  Insert  Window Select  Row 1, Column 1 - 18 Note River Boundary Cells

7. Select: BCs  Constant Head Boundary Select: BCs  Insert  Window Select: Row 40, Column 1 - 18 Set value to – Boundary Head = 1000 m Add Constant Head Boundary Conditions Constant Head Boundary Cell

8. Select: Properties  Recharge Select: Property Values  Database Set up 1 zone: Recharge = 0.001 m/day Click OK Edit Database – Recharge

9. Select: Props  Recharge Select: Props  Set Value or Zone  Window Start in upper right-hand corner and drag to select all cells in grid Click OK Select: Zone Number 1 Click OK Assign Recharge Values to Layers

10. Select: Model  MODFLOW  Packages Change: Root File Select: OK Create MODFLOW Dataset

11. Select: Model  MODFLOW  Package Options Select: Length Units = meters OK Create MODFLOW Dataset

12. Select: Model  MODFLOW  Package Options Select: Tab  Initial Heads Enter: 1000 ft Select: OK Create MODFLOW Dataset

13. Select: Model  MODFLOW  Package Options Select: Tab  BCF-LPF Select: Layer 1 as “UnConfined” Select: OK Create MODFLOW Dataset

14. Select: Model  MODFLOW  Package Options Select: Tab  Recharge - ET Select: Top Layer Select: OK Create MODFLOW Dataset

15. Select: Model  Paths to Models Select: C:\your_directory\work Create Working Directory

16. Run Simulation Select: Calculator button Would you like to process the results? Select: Yes Select: Cell-by-cell flows Select: Contour Water Table in Layer 1

17. Part B

18. Add Well Boundary Conditions Select BCs  Well Select BCs  Insert  Single Cell Use cursor to click on cell at Row 6, Column 9 Enter “Flow Rate in Well” = -18,000 m3/day Select OK Note

19. Part C

20. Transient Model S y = 0.1 One year of continuous pumping Stress periods – Use 12 stress periods, one for each month of the year, and 31 time steps per stress period – Length of each stress period = number of days in that month – Tme step multiplier (TSMULT) = 1.0 Copy Recharge Rate for each of the 12 stress periods Initial heads = file (*.hds) from Part (a).

21. Transient Model Convert you steady-state model to a transient model Open your model Select: Model  MODFLOW  Package Options Select: Basic Package Tab Uncheck: Steady-State checkbox Enter: Number of stress periods = 12 Select: Days Select: OK Do you want to copy data? Select: Yes Do you want to set up stress periods? Select: Yes

22. Stress Periods Use 12 stress periods, one for each month of the year Time steps per stress period = number of days in the month Length of each time step = 1 day Tme step multiplier = 1.0

23. Pumping Conditions Select: BC  Well Select: BC  Modify  Layer Uncheck: “Steady-state Boundary Condition” Press: “Transient Data” Uncheck this box Press this button

24. Pumping Conditions Enter: Starting and Ending Stress Period Numbers Enter: Q = -18000 m 3 /d for stress periods 5 - 9

25. Setting heads from *.hds file Select: Model  MODFLOW  Package Options Select: Tab  Initial Heads Select: Initial Head Location Select: “Read heads directly from binary head-save file” Select: Browse Find: Your heads form Part (a) in a file with the extension “.hds”, for example, “Parta.hds” Select: OK

26. Run Simulation Select: Calculator button Would you like to process the results? Select: Yes Select: Cell-by-cell flows