Modeling Percolation from Multiple Ponds in Close Proximity Using ICPR. The ASCE Suncoast Branch Water Resources Luncheon Sarasota, Florida

Transcription

1 Modeling Percolation from Multiple Ponds in Close Proximity Using ICPR Peter J. Singhofen, P.E. Streamline Technologies, Inc. presented at The ASCE Suncoast Branch Water Resources Luncheon Sarasota, Florida April 23, , Streamline Technologies, Inc.

2 Three Ponds in Close Proximity

3 Ideally, A 2D Model Would Be Appropriate

4 Let s See How We Can Model This With PercPack TM

5 Before Examing Multiple Ponds, Let s Take a Look at How Percolation from a Single Isolated Pond is Modeled Using PercPack TM.

6 Surface Runoff Drainage Basin Pond Pond Water Table Aquifer Base Percolation Link Aquifer ICPR Schematic

7 450 A Computational Framework for a 100 Square Pond A 50 P2 P1 500 P3 Percolation Link Parameters

8 Pond Bottom (el. 100 ) Section A-A 50 (10 cells) 450 (45 cells) Water Table (el. 96 ) Aquifer Base (el. 88 ) P1 P2 P3

9 Vertical Unsaturated Flow Perc Rates are Based on Exposed Surface Area and Vertical Conductivity. P1 P2 P3

10 Horizontal Saturated Flow Perc Rates are Based on a Finite Difference Solution to Darcy s Law and Conservation of Mass. P1 P2 P3

11 Parameters Related to the Surficial Aquifer

12 The Water Table Elevation is used to initialize each finite difference cell.

13 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.

14 The Layer Thickness is the length of the unsaturated zone directly below the bottom of the pond. If it is set to a very small value or zero, no vertical unsaturated flow will occur.

15 Surface Area Option used for Vertical Unsaturated Flow. Vertical Flow Termination used for Transition to Horizontal Saturated Flow.

16 Example Hydrologic Data Set Drainage Basin Data Area: 5 acres N-DCIA Curve Number: 65 DCIA: 23% TC: 20 minutes Peak Factor: 323 Storm Data Distribution: Florida Modified Total Rainfall: 8.6 Duration: 24 hours

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23 Now, Let s Examine 2 Identical Ponds In Very Close Proximity.

24 Two Identical Ponds 50 Apart (Computational Rings Overlap) 50

25 Drainage Basin 1 Drainage Basin 2 Pond 1 Pond 2 Percolation Link 1 Percolation Link 2 Aquifer ICPR Schematic (Perc Links are Independent)

26 Groundwater Mounds Begin to Collide

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31 The Cross-Hatched Area Represents Double Accounting of Soil Storage

32 This is a More Accurate Representation of the System.

33 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 high conductivities require additional considerations that are beyond the scope of this presentation.

34 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 high conductivities require additional considerations that are beyond the scope of this presentation.

35 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 high conductivities require additional considerations that are beyond the scope of this presentation.

36 Treat Ponds as a Single System, Then Proportion the Perimeters Assume Vertical Wall Between Ponds P2 P1 P1 P2 P3 P3

37 Adjusting the Computational Framework (Perc Link Data Forms) Single Pond Dual Ponds in Very Close Proximty

38 Adjusted Adjusted Unadjusted

39 106 Drawdown Time Impacts 104 Dual Ponds in Very Close Proximty Single Independent Pond 50h 100h 150h 200h 250h

40 Next, Let s Examine 3 Identical Ponds In Very Close Proximity.

41 Three Ponds 50 Apart 50 50

42 Drainage Basin 1 Drainage Basin 2 Drainage Basin 3 Pond 1 Pond 2 Pond 3 Percolation Link 1 Percolation Link 2 Percolation Link 3 Aquifer ICPR Schematic (Perc Links are Independent)

43 Groundwater Mounds Collide

44 Treat Ponds as a Single System, Then Proportion the Perimeters P2 1 P1 1 P1 2 P1 3 P2 3 P2 2 P3 1 P3 3 P3 2

45 Adustments to Perimeters for Three-Pond System Single Independent Pond Left & Right Ponds Center Pond Perimeter Perimeter Perimeter

46 Center Pond Left & Right Ponds Single Independent Pond

47 106 Center Pond 104 Left & Right Ponds 102 Single Independent Pond h 100h 150h 200h 250h

48 Same 3-Pond Example Except Connect the Ponds on the Surface With Equalizer Pipes.

49 Drainage Basin 1 Drainage Basin 2 Drainage Basin 3 Pond 1 Pipe 2-1 Pond 2 Pipe 2-3 Pond 3 Perc Link 1 Perc Link 2 Perc Link 3 Aquifer ICPR Schematic (Add Equalizer Pipes)

50 106 Center Pond, No Equalizer Pipes 104 All 3 Ponds, With Equalizer Pipes 102 End Ponds, No Equalizer Pipes h 100h 150h 200h 250h

51 Another 3-Pond Example One Center Pond Surrounded by Two Perimeter Ponds with Equalizer Pipes.

52 Center Pond with Two Perimeter Ponds Center Pond 1 Perimeter Pond 2 Perimeter Pond 3 Equalizer Pipes

53 Treat System as Single Pond, Merge Computational Rings for the Perimeter Ponds and then Proportion P1 2 P1 3 P2 2 P2 3 P3 2 P3 3 Horizontal Flow from the Center Pond Must be Prevented, Therefore no Perimeters are Required.

54 Prevent Horizontal Flow from Center Pond by Setting the Vertical Flow Termination Option to Constant Rate with a Rate of Zero.

55 Drainage Basin 1 Drainage Basin 2 Drainage Basin 3 Center Pond 1 Pipe 1-2 Perimeter Pond 2 Pipe 2-3 Perimeter Pond 3 Perc Link 1 (no horz flow) Perc Link 2 Perc Link 3 Aquifer ICPR Schematic

56 Two Identical Ponds, But Not in Very Close Proximity

57 Two Ponds 250 Apart (not in very close proximity) 250

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64 Drainage Basin 1 Drainage Basin 2 Pond 1 Pond 2 Perc Link 1A Perc Link 1B Perc Link 2B Perc Link 2A Aquifer ICPR Schematic (Perc Links are Independent)

65 Use Two Perc Links per Pond and Proportion the Perimeters Accordingly

66 Adustments to Perimeters for Two-Pond/Four-Perc Link System Single Independent Pond Perc Links 1A & 2A Perc Links 1B & 2B Perimeter Perimeter Perimeter

67 Perc Links 1A & 2A Perc Links 1B & 2B

68 Perc Links 1A & 2A Zero recharge forces a fixed head boundary condition at the P3 ring. This parameter affects soil storage and vertical unsaturated flow. Perc Links 1B & 2B A non-zero recharge rate forces a zero flow boundary condition at the P3 ring. A very small layer thickness prevents vertical unsaturated flow.

69 Mounding Impacts for Perc Links 1A & 2A (fixed head boundary condition) Near P1 Ring Near P2 Ring 98 Near P3 Ring Returns to Original W.T h 4000h 6000h 8000h

70 104 Near P1 Ring Mounding Impacts for Perc Links 1B & 2B (no flow boundary condition) 102 Near P2 Ring Near P3 Ring Levels Out 2.9 Above W.T h 1000h 1500h

71 Only Perc Link 1A 102 Perc Links 1A & 1B h 100h 150h 200h 250h

72 Now Back to the Original Three-Pond System.

73 Three Ponds in Close Proximity

74 Groundwater Flow is Radially Outward P3 Ring

75 Overlapping Radii of Influence P3 Rings

76 Shaded Areas Represent Overlap

77 Merge Computational Rings and Proportion

78 Coverage for Primary Perc Links A Single Perc Link Per Pond Can Be Used To Model GW Movement Away From Ponds

79 Small Overlap Areas Overlap

80 Secondary Perc Links Can Be Used To Model GW Movement Between Ponds Secondary Perc Links

81 Primary Perc Link (use fixed head boundary condition) Note: Fixed Head B.C. is established by setting annual recharge to zero. Secondary Perc Link (use no flow boundary condition) Note: No Flow B.C. is established by setting annual recharge to very small non-zero number.

82 Primary Perc Link (use fixed head boundary condition) Secondary Perc Link (use no flow boundary condition)

83 Primary Perc Link (use fixed head boundary condition) Secondary Perc Link (use no flow boundary condition)

84 Drainage Basin 1 Drainage Basin 3 Drainage Basin 2 Pond 1 Pond 3 Pond 2 Perc 1B Perc 1A (no flow) (fixed head) Perc 3B (no flow) Perc 3A (fixed head) Perc 2B (no flow) Perc 2A (fixed head) Aquifer ICPR Schematic (Perc Links are Independent)

85 QUESTIONS?