Patapsco/Back River SWMM Model Part II – SWMM Water Quality Calibration Maryland Department of the Environment

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

Water Quality Calibration Urban 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 =  (Flow*Conc.) –EMC =  Load /  Flow Results –Unique Solution of Buildup Rate Validation –Timeseries Comparision

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) R=Rainfall Energy (from BWI) K=Soil Erodibility (Soil type) LS=Slope Length Gradient Ratio (DEM) C=Cropping Management Factor (Landuse – Calibrated) P=Erosion Control Practice (Literature) Delivery Ratio –Applied Based on Subwatershed Drainage to Baltimore Harbor Parameter –Adjusted cropping management factor within recommended values

Event Mean Concentration References

Unit Load References

Water Quality Data -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 *All data collected by Baltimore City

SWMM Baseflow Concentration Base Flow Data SourceTSSCrZnPb Baltimore County NPDES Report (2000)X Baltimore City NPDES Report (2001)X Baltimore City Wastewater Facilities Master Plan (1997)XXX Baltimore County DEPRM Watershed Monitoring Project ( )X MDE Upper Western Shore Monitoring Project (2001)X References Concentrations

Results

Jones Falls

Patapsco

Back River

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

Sub-Watershed Loads

Baltimore Harbor Watershed Land Use Loading Summary CBP TSS Results (93-97) Urban: 44.5% Crop: 28.4% Pasture: 4.1% Forest: 23.1%

Comparative Analysis - Existing Studies

SWMM Calibration Summary & Conclusions Focus on predominant land use for model calibration Calibrate EOS loads to mean literature values Calibration urban EMC’s 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