PatapscoBack River SWMM Model

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Patapsco/Back River SWMM Model

• Part II SWMM Water Quality Calibration
• Maryland Department of the Environment

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Water Quality Calibration

• General
• Aggregate Five Subwatersheds
• Focus on predominant land uses
• Calibrate EOS loads to literature values
• Calibrate Event Mean Concentrations
• Detailed
• Time series overlay
• Comparative Analysis

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Water Quality CalibrationUrban TSS and Metals

• Objective
• EMC (statistics of wet-weather events)
• Unit Load (annual)
• Parameters
• Buildup Rate (Linear - Calibrated)
• Build Limit (Set high)
• Wash-off Coefficient (Based on Literature)
• Wash-off Exponent (Based on Literature)
• Calculation
• Load ? (FlowConc.)
• EMC ? Load / ? Flow
• Results
• Unique Solution of Buildup Rate
• Validation
• Timeseries Comparision

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Water Quality Calibration Non-Urban Land Use
(USLE)

• Calibration Objective
• Correlate with long term loading rate estimates
• USLE Estimates gross long term erosion rate
• Parameters (Land use specific)
• RRainfall Energy (from BWI)
• KSoil Erodibility (Soil type)
• LSSlope Length Gradient Ratio (DEM)
• CCropping Management Factor (Landuse
  Calibrated)
• PErosion Control Practice (Literature)
• Delivery Ratio
• Applied Based on Subwatershed Drainage to
  Baltimore Harbor
• Parameter
• Adjusted cropping management factor within
  recommended values

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Event Mean Concentration References
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Unit Load References
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Water Quality Data
All data collected by Baltimore City
-DNR Core station TSS data available at stations
240, 230 and 211 (Data set contains mostly base
flow samples) - Metals values not shown from
2/25/95 to 12/1/96 due to high detection limits
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SWMM Baseflow Concentration
References
Base Flow Data Source
TSS
Cr
Zn
Pb
Baltimore County NPDES Report (2000)
X
Baltimore City NPDES Report (2001)
X
Baltimore City Wastewater Facilities Master Plan
(1997)
X
X
X
Baltimore County DEPRM Watershed Monitoring
Project (1997-2000)
X
MDE Upper Western Shore Monitoring Project (2001)
X
Concentrations
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Results
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Jones Falls
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Patapsco
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Back River
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Best Management Practices (BMPs)

• Uncertainty and variability in EMC
• Instream sites from NPDES Report
• Timeseries comparison of model vs data show
  reasonable concentration magnitude agreement
• BMPs not explicitly included in model
• Established a baseline load scenario

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Sub-Watershed Loads
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Baltimore Harbor Watershed Land Use Loading
Summary
CBP TSS Results (93-97) Urban 44.5 Crop
28.4 Pasture 4.1 Forest 23.1
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Comparative Analysis - Existing Studies
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SWMM Calibration Summary Conclusions

• Focus on predominant land use for model
  calibration
• Calibrate EOS loads to mean literature values
• Calibration urban EMCs to reported mean landuse
  values
• Overlay model with water quality timeseries data
• Comparative Analysis
• Model supports overall trends (Flow, TSS and
  metals)
• Next - Sensitivity of water quality model to NPS
  Loads