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Modeling Percolation from Multiple Ponds in Close Proximity Using ICPR
Peter J. Singhofen, P.E.Streamline Technologies, Inc.
presented at
The ASCE Suncoast BranchWater Resources Luncheon
Sarasota, Florida
April 23, 2009
©2009, Streamline Technologies, Inc.www.streamnologies.com
Three Ponds in Close Proximity
Ideally, A 2D Model Would Be Appropriate
Let’s See How We Can Model This With PercPackTM
Before Examing Multiple Ponds,Let’s Take a Look at How
Percolation from a Single IsolatedPond is Modeled Using PercPackTM.
Pond
Water Table
Aquifer Base
Pond
Aquifer
Percolation Link
ICPR Schematic
Surface Runoff Drainage Basin
P2
P3
P1
50’
500’
450’
ComputationalFramework for a100’ Square Pond
Percolation Link Parameters
A A’
P1 P2 P3
Aquifer Base (el. 88’)
Water Table (el. 96’)
Pond Bottom (el. 100’)
50’ (10 cells)
450’ (45 cells)
Section A-A’
P1 P2 P3
Vertical Unsaturated Flow
Perc Rates are Based on Exposed Surface Area and Vertical Conductivity.
P1 P2 P3
Horizontal Saturated Flow
Perc Rates are Based on a Finite Difference Solution to Darcy’s Law and
Conservation of Mass.
Parameters Related to the Surficial Aquifer
The “Water Table Elevation” is usedto initialize each finite difference cell.
If the “Annual Recharge Rate” is zero,a “fixed head boundary condition” is used at the P3 ring. Otherwise, a “zero flow boundary condition” is used.
The “Layer Thickness” is the length ofthe unsaturated zone directly below thebottom of the pond. If it is set to a verysmall value or zero, no vertical unsaturated flow will occur.
“Surface Area Option” used for VerticalUnsaturated Flow.
“Vertical Flow Termination” used forTransition to Horizontal Saturated Flow.
Drainage Basin Data
Area: 5 acresN-DCIA Curve Number: 65DCIA: 23%TC: 20 minutesPeak Factor: 323
Storm Data
Distribution: Florida ModifiedTotal Rainfall: 8.6”Duration: 24 hours
Example Hydrologic Data Set
Now, Let’s Examine 2 Identical PondsIn “Very” Close Proximity.
50’
Two Identical Ponds 50’ Apart(Computational Rings Overlap)
Pond 2
Aquifer
Percolation Link 2
ICPR Schematic(Perc Links are Independent)
Drainage Basin 2
Pond 1
Percolation Link 1
Drainage Basin 1
Groundwater Mounds Begin to Collide
The Cross-Hatched AreaRepresents Double Accounting of Soil
Storage
This is a More Accurate Representation of the
System.
The Approach Presented on the Following Slides Works Well When:
1. There are mild gradients between ponds
2. The horizontal conductivity is not exceptionally high
Steep gradients and/or super highconductivities require additional considerations that are beyond the scope of this presentation.
The Approach Presented on the Following Slides Works Well When:
1. There are mild gradients between ponds
2. The horizontal conductivity is not exceptionally high
Steep gradients and/or super highconductivities require additional considerations that are beyond the scope of this presentation.
The Approach Presented on the Following Slides Works Well When:
1. There are mild gradients between ponds
2. The horizontal conductivity is not exceptionally high
Steep gradients and/or super highconductivities require additional considerations that are beyond the scope of this presentation.
Treat Ponds as a Single System, Then Proportion the Perimeters
P1P2
P3
P1’ P2’
P3’
Assume Vertical Wall Between Ponds
Single Pond Dual Ponds in “Very” Close Proximty
Adjusting the Computational Framework(Perc Link Data Forms)
Unadjusted
Adjusted Adjusted
Single Independent Pond
Dual Ponds in “Very” Close Proximty
Drawdown Time Impacts
104’
106’
102’
100’50h 100h 150h 200h 250h
Next, Let’s Examine 3 Identical PondsIn “Very” Close Proximity.
50’
Three Ponds 50’ Apart
50’
Aquifer
ICPR Schematic(Perc Links are Independent)
Pond 3
Percolation Link 3
Drainage Basin 3
Pond 1
Percolation Link 1
Drainage Basin 1
Pond 2
Percolation Link 2
Drainage Basin 2
Groundwater Mounds Collide
P11P21
P31
P12
P22
P32
P33
P23P13
Treat Ponds as a Single System, Then Proportion the Perimeters
Adustments to Perimetersfor Three-Pond System
3542’
714’
400’
SingleIndependent
Pond
300’1921’Perimeter 3
300’507’Perimeter 2
200’300’Perimeter 1
CenterPond
Left & Right Ponds
SingleIndependent
Pond
Left & RightPonds
Center Pond
Single Independent Pond
Left & Right Ponds
Center Pond
104’
106’
102’
100’50h 100h 150h 200h 250h
Same 3-Pond Example Except Connect the Ponds on the Surface
With Equalizer Pipes.
Aquifer
ICPR Schematic(Add Equalizer Pipes)
Pond 3
Perc Link 3
Drainage Basin 3
Pond 1
Perc Link 1
Drainage Basin 1
Pond 2
Perc Link 2
Drainage Basin 2
Pipe 2-1
Pipe 2-3
104’
106’
102’
100’
50h 100h 150h 200h 250h
Center Pond, No Equalizer Pipes
End Ponds,No Equalizer Pipes
All 3 Ponds,With Equalizer Pipes
Another 3-Pond Example One Center Pond Surrounded by Two
Perimeter Ponds with Equalizer Pipes.
Center Pond with Two Perimeter Ponds
Perimeter Pond 3
EqualizerPipes
Perimeter Pond 2
CenterPond 1
Treat System as Single Pond, Merge Computational Rings for the Perimeter Ponds and then Proportion
P12
P22
P32
P33
P23
P13
Horizontal Flow from the Center Pond Must be
Prevented, Therefore no Perimeters are Required.
Prevent Horizontal Flow from Center Pond by Setting the “Vertical Flow Termination” Option to “Constant
Rate” with a Rate of Zero.
Aquifer
ICPR Schematic
PerimeterPond 3
Perc Link 3
Drainage Basin 3
CenterPond 1
Perc Link 1(no horz flow)
Drainage Basin 1
PerimeterPond 2
Perc Link 2
Drainage Basin 2
Pipe 1-2
Pipe 2-3
Two Identical Ponds,But Not in “Very” Close Proximity
Two Ponds 250’ Apart(not in “very” close proximity)
250’
Aquifer
ICPR Schematic(Perc Links are Independent)
Pond 1
Perc Link 1A
Drainage Basin 1
Pond 2
Drainage Basin 2
Perc Link 1B
Perc Link 2A
Perc Link 2B
50’ 75’
50’
450’
500’
Use Two Perc Links per Pond and Proportion the Perimeters Accordingly
Adustments to Perimetersfor Two-Pond/Four-Perc Link System
3542’
714’
400’
SingleIndependent
Pond
375’1921’Perimeter 3
207’507’Perimeter 2
100’300’Perimeter 1
Perc Links1B & 2B
Perc Links1A & 2A
Perc Links 1A & 2A Perc Links 1B & 2B
Zero recharge forces afixed head boundarycondition at the P3 ring.
A non-zero recharge rate forces a zeroflow boundary conditionat the P3 ring.
This parameter affectssoil storage and verticalunsaturated flow.
A very small layer thick-ness prevents verticalunsaturated flow.
Perc Links 1A & 2A
Perc Links 1B & 2B
Mounding Impactsfor
Perc Links 1A & 2A(fixed head boundary condition)
Near P1 Ring
Near P2 Ring
Near P3 Ring
Returns toOriginal
W.T.
104’
102’
100’
98’
96’2000h 4000h 6000h 8000h
106’
Near P1 Ring
Near P2 Ring
Near P3 Ring
Levels Out2.9’ Above
W.T.
Mounding Impactsfor
Perc Links 1B & 2B(no flow boundary condition)
104’
102’
100’
98’
96’500h 1000h 1500h
104’
102’
100’
106’
50h 100h 150h 200h 250h
Only Perc Link 1A
Perc Links 1A & 1B
Now Back to the Original Three-Pond System.
Three Ponds in Close Proximity
Groundwater Flow is Radially Outward
P3 Ring
Overlapping Radii of Influence
P3 Rings
Shaded Areas Represent Overlap
Merge Computational Rings and Proportion
Coverage for Primary Perc LinksA Single Perc Link Per Pond Can Be Used To Model GW Movement Away From Ponds
Small Overlap Areas
Overlap
Secondary Perc Links Can Be Used To Model GW Movement Between Ponds
Secondary Perc Links
Secondary Perc Link(use no flow
boundary condition)
Primary Perc Link(use fixed head
boundary condition)
Note: Fixed Head B.C. is established by setting annual recharge to zero.
Note: No Flow B.C. is established by setting annual recharge to very small non-zero number.
Secondary Perc Link(use no flow
boundary condition)
Primary Perc Link(use fixed head
boundary condition)
Secondary Perc Link(use no flow
boundary condition)
Primary Perc Link(use fixed head
boundary condition)
Aquifer
ICPR Schematic(Perc Links are Independent)
Pond 1
Perc 1A(fixed head)
Drainage Basin 1
Perc 1B(no flow)
Pond 2
Drainage Basin 2
Perc 2A(fixed head)
Perc 2B(no flow)
Pond 3
Drainage Basin 3
Perc 3A(fixed head)
Perc 3B(no flow)
QUESTIONS?
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