Groundwater Modeling – 2:Computer Implementation

Groundwater Hydraulics

Daene C. McKinney

Groundwater Vistas• Groundwater Modeling

Environment– Graphic User Interface (GUI)

for MODFLOW and other models

– Imports a wide variety of files• MODFLOW data sets• ArcView shapefiles• Digitized map files (AutoCAD

DXF, Shapefiles, and SURFER)

• GroundwaterVistas is not MODFLOW (but includes it)

• MODFLOW has no Graphic User Interface (GUI)

Groundwater Vistas Installation

• Download file: gv5final.zip from

– http://www.caee.utexas.edu/prof/mckinney/ce374l/Overheads/gv5final.zip

• Unzip gv5final.zip to get– gv5final.exe (a “setup” file)

• Run gv5final.exe to install – Groundwater Vistas version 5– Answer “yes” or “OK” to

everything

• Groundwater Vistas manuals installed in– C:\gwv5\manuals

Unit System

• Use a consistent set of units for all data• Select a unit of length and time

– Hydraulic conductivity (K) in m/s– Pumping rates (Q) in m3/s– Length units in m– Elevations in m

Example• Boundaries

– North & South: No-flow– East & West: Constant-head

• Layer 1 – unconfined (13 m)– Kh = 5x10-3 m/s

– Kv = 5x10-4 m/s

• Layer 2 – confined (5 m)– Kh = 1x10-3 m/s; Kv = 1x10-4 m/s

No-flow Boundary

No-flow Boundary

Co

nst

an

t H

ea

d B

ou

nd

ary

(h

= 9

m)

Co

nst

an

t H

ea

d B

ou

nd

ary

(h

= 8

m)

Pumping Well

60

0 m

600 mAdapted from Chiang, W-H and W. Kinzelbach, Processing Modflow: A Simulation System For Modeling Groundwater Flow and Pollution, 1996

Pumping Well

Layer 1

Layer 2

513

10 m

-3 m-8 m

N

Create a New Model• Start the GV program• Select File New

Create a New Model• Enter basic information

– 30 rows– 30 columns– Row spacing = 20 m– Column spacing = 20 m– Top of Layer 1 = 10 m– Bottom of Layer 1 = -3 m– Bottom of Layer 2 = -8 m

Press

Model Grid

Elevation = +10 mElevation = -3 m

Elevation = -8

Add Constant Head Boundary Conditions• Select: Layer 1• Select: BCs Constant Head Boundary • Select: BCs Insert Window• Hold left Mouse button and Drag cursor through

cells in Column 1• Set value to 9 m

Constant Head Boundary Cells(h = 9 m)

Top Layer - 1

Press OK

Repeat for Boundary in Column 30• Select: Layer 1• Select: BCs Constant Head Boundary • Select: BCs Insert Window• Hold left Mouse button and Drag cursor

through cells in Column 30• Set value to 8 m Constant Head

Boundary Cells(h = 8 m)

Top Layer - 1

Repeat for Layer 2• Select: Layer 2• Select: BCs Constant Head Boundary • Select: BCs Insert Window• Hold left Mouse button and Drag cursor

through cells in Columns 1 and 30• Set values to 9 and 8 m

Constant Head Boundary Cells(h = 8 m)

Bottom Layer - 2

Add Hydraulic Conductivity• Select: Props Hydraulic Conductivity• Select: Property Values Database• Set up 2 zones:

– Layer 1• Kx = 5x10-3 m/s

• Ky = 5x10-3 m/s

• Kz = 5x10-4 m/s

– Layer 2• Kx= 1x10-3 m/s

• Ky = 1x10-3 m/s

• Kz = 1x10-4 m/s• Click OK

Assign K to Layer 1• Select: Layer 1• Select: Props Hydraulic Conductivity• Select: Props Set Value or Zone Window• Start in upper right-hand corner and drag to select all cells in grid• Select: OK• Select: Zone Number 1• Select: OK

Assign K to Layer 2• Select: Layer 2• Select: Props Hydraulic Conductivity• Select: Props Set Value or Zone Window• Start in upper right-hand corner and drag to select all cells in grid• Select: OK• Select: Zone Number 2• Select: OK

Add Multi-Layer Well

• Well penetrates all layers• Total pumping rate for multilayer well is sum of pumping from

layers• Pumping for each layer (Qk) is proportional to layer

transmissivity (bK)

• For a total pumping rate of Qtotal = 0.02 m3/s– Q1 = 0.0185 m3/s

– Q2 = 0.0015 m3/s

2211 KbKb

KbQQ kktotalk

Pumping Well

Layer 1

Layer 2

Add Well in Layer 1• Select: Layer 1• Select: BCs Well• Select: BCs Insert Single Cell• Use cursor to click on cell at Row 15, Col. 25• Enter “Flow Rate in Well” = - 0.0185 m3/s• Select: OK

Row 15, Column 25

Note Top Layer - 1

Add Well in Layer 2• Select: Layer 2• Select: BCs Well• Select: BCs Insert Single Cell• Use cursor to click on cell at Row 15, Col. 25• Enter “Flow Rate in Well” = - 0.0015 m3/s• Select: OK

Row 15, Column 25

Note Top Layer - 1

Create MODFLOW Dataset• Select: Model MODFLOW Package Options• Select: Time Units = seconds• Select: Length Units = meters

Create MODFLOW Dataset• Select: Model MODFLOW Package Options• Select: Tab Initial Heads• Enter: 0 ft for both Layers

Create MODFLOW Dataset• Select: Model MODFLOW Package Options• Select: Tab BCF-LPF• Select: Layer 1 as “Unconfined”• Select: Layer 2 as “Confined”

Create MODFLOW Dataset• Select: Model MODFLOW Package Options• Select: Tab Recharge - ET• Select: Top Layer Only• Select: OK

Run Simulation• Select: Calculator button• Select: Yes, Yes, Yes!

Process Results• Select: Cell-by-cell flows

Results• Select: Plot Contour

Parameters (Plan)• Set parameters to

achieve the display you like

Set Display Options• Select: Plot What to display• Select: Display Color Flood of Head• Select: Display Legend • Select: OK

Set Legend Options• Select: Plot Legend Options• Select: Contents• Select: Color Flood Scale• Select: Dry Cells• Select: Title• Select: Title Font = 10 bold• Select: Text Font = 10• Select: OK

Results

Results• Look for the file ‘Ex1.lst” in the directory that you specified for the “working

directory” (e.g., C:\gv5\models).• Look for the following table and make sure you get the same (or close) numbers