Nitrogen Modeling Applications

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Nitrogen Modeling Applications
Bruce F. Douglas, P.E. NOWRA Nitrogen
Sympsium April 7, 2007
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Concepts

• 1 Examples of Nitrogen Models
• 2 Mass Balance Model (Pinelands, New Jersey)
• 3-Dimensional Groundwater Model (Malibu,
  California)
• Physically-based Watershed Model (Green Hill
  Pond, Rhode Island)
• 5 Linked Module Approach (Massachusetts
  Estuary Project)

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Pinelands Area
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Decentralized and Centralized Wastewater
Management
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Pinelands Ambient Standard 2 mg/L Nitrate-N
Pilot Study
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Malibu Civic Center Area
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Malibu Lagoon Flooded Breached Conditions
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Malibu Creek Watershed
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Malibu Lagoon Conceptual Model

• Source M acDonald M orrissey, 2001

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Existing Information
Bedrock, Terrace Landslide Deposits Floodplain
Alluvium Alluvium Beach Deposits

• Source Yerkes and Campbell, 1980

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Synoptic Water Level Data
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Groundwater Time of Travel Flooded Lagoon
Condition
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Groundwater Time of Travel Breached Lagoon
Condition
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Future Nitrogen Loading to Lagoon
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Green Hill Pond - Rhode Island
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Soil Water Assessment Tool (SWAT)

• Precipitation

• Evaporation and Transpiration

• Surface Runoff

• Root Zone

• Infiltration/plant uptake/ Soil moisture
  redistribution

• Lateral Flow

• Vadose
• (unsaturated) Zone

• Revap from shallow aquifer

• Percolation to shallow aquifer

• Shallow (unconfined) Aquifer

• Return Flow

• Confining Layer

• Flow out of watershed

• Deep (confined) Aquifer

• Recharge to
• deep aquifer

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Green Hill Pond Watershed
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Caption or reference
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Hydrology Soils Land Use Hydrologic
Response Unit (HRU)
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Concentrated Sources of Nitrogen in Green Hill
Pond Watershed
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Green Hill Pond Current Conditions
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Green Hill Pond Build-Out Conditions
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Massachusetts Estuary Project

• 89 Estuaries
• 3 Years of Field Data Collection
• Multiple Linked Modules
• Consistent Methodology

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Massachusetts Estuaries Project
Source MEP
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Marthas Vineyard, Massachusetts
Source Marthas Vineyard Commission
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MEP Linked Watershed-Embayment Approach

• Stream Flow - N Load

• Watershed Delineation Model

• Tide Elevation
• Bathymetry
• Currents

• Recycled N
• Watercolumn N

• Watershed N Loading Model

• Hydrodynamic Model

• Total Nitrogen Model

• N Management Scenarios (MEP Tech Team)

• D.O., Eelgrass Infauna Surveys

• Thresholds Development
• (N Target)

• TMDL (DEP) Clean Water Act

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Take Away Points

• Gather Existing Data
• Collect New Field Data as needed
• Focus on Physical Flow Characteristics
• Select M odel Appropriate for Local Conditions
• Step Back and Look at the Big Picture
• Calibrate
• Conduct Sensitivity Analyses
• Follow-up with M onitoring and Verification

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Thank Y ou!
Bruce F. Douglas, P.E. Stone Environmental,
Inc Montpelier, Vermont bdouglas_at_stone-env.com
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Pinelands Nitrate/N vs. Lot Size
New Jersey Pinelands Commission