Lower Lakes and Murray River Modelling (Virtual Weir Presentation / Discussion)

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Lower Lakes and Murray River Modelling(Virtual
Weir Presentation / Discussion)

• Canberra
• 11 February 2009

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To be Discussed

• Existing Modelling
• RMA (2D) and ELCOM (3D) Modelling of Virtual and
  Partial Weir Simulations
• Model Setup
• Model Validation
• Model Results Animations
• Model Uncertainty
• Empirical Calculations
• Destratification / Richardson Number
  Calculations
• Seiche Volumes

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Model Setup/Extents

• RMA 2D (Blue) All areas upstream of Tidal
  Barrages Downstream of Lock 1, Lake Albert
  disconnected
• ELCOM 3D (Green) From Pomanda Island (upstream
  of weir location) to Murray Bridge
• RMA simulation executed first, then results fed
  to ELCOM (U/S D/S Boundaries)

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Model Validation

• Validation period 1/1/2008 14/7/2008
• Objectives
• Best match observed hydrodynamics (WL) and
  salinity
• Ensure key processes appropriately represented
• Understanding of model uncertainty
• Key Uncertainties
• Additional salt load along length of River
• Additional irrigation demands / groundwater
  losses?

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Predicted Water Levels Poltalloch Plains
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Predicted River Salinity Woods Point
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Predicted Lake Salinity Spatial Validation
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Predicted Lake Salinity Spatial Validation
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Predicted 3D River Salinity Wellington
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Predicted 3D River Temperature Wellington
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Comparison Measured vs Modelled River Salinity
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2 yr Prognostic Simulations

• Examining what may happen in the future, given
  continuing high net evaporation (1982) levels,
  and variations in the South Australias border
  allocation (Border Allocations of 696, 796 and
  896 GL/yr), through to the end of 2010.
• Simulations aimed at maintaining Lake Level at
  -1.3mAHD.
• Salt water introduced through Goolwa Barrage in
  October 2009.
• Stop logs positioned by-monthly based on water
  level balance calculation.

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Predicted Water Levels Lake Alexandrina
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Timeseries Locations Lake Alexandrina
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Predicted Lake (2D) Salinities Point 1
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Predicted Lake (2D) Salinities Point 5
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Predicted Lake (2D) Salinities Point 6
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Predicted River (3D) Salinities Wellington
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Predicted River (3D) Salinities Tailem Bend
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Predicted River (3D) Salinities Swanport
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Animation Lower Lakes 696 GL/yr
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Animation Lower Lakes 696 GL/yr
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Animation River (696 GL/yr)
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Animation River (696 GL/yr)
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Animation River (796 GL/yr)
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Animation River (796 GL/yr)
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Animation River (896 GL/yr)
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Animation River (896 GL/yr)
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Comparison at End 2010
696 GL/yr
796 GL/yr
896 GL/yr
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Uncertainty

• Model can still be improved
• Validation only currently till Mid July 2008 (no
  destratification period)
• No validation data for low level and high salt
  available
• Uses 1 year (2007) wind (cannot predict future
  wind conditions)
• Wind spatially homogenous

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Partial Closure Weir Simulations

• No Weir
• 1100m Gap
• 700m Gap
• 300m Gap
• 100m Gap

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Simulated Water Level in Lake Alexandrina
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Simulated Salinity (ppt) Wellington Bed
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Pomanda Embayment Bathymetry
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Other Info