LCFR Water Quality Modeling Project Report

1
LCFR Water Quality ModelingProject Report

• Jim Bowen, UNC Charlotte
• LCFRP Advisory Board/Tech. Comm. Meeting, October
  30, 2008
• Raleigh, NC

2
Outline of Presentation

• A Quick Review of the LCFR Model
• Summary of Model Report
• Questions/Suggestions

3
Basis of PresentationTechnicalReportDraft(av
ailable on web)
4
LCFR Dissolved Oxygen ModelThe big picture
Met Data
Air temps, precip, wind, cloudiness
Hydrologic Conditions
River Flows, Temps, Concs Tides
Time
Estuary Physical Characteristics e.g.
length, width, depth, roughness
Time
EFDC Software Adjustable Parameters (e.g. BOD
decay, SOD, reaeration)
State Variables
nutrients DO, organic C
Time
5
Dissolved Oxygen Conceptual Model BOD Sources
Cape Fear, Black NECF BOD Load
decaying phytopl.
Estuary Inflow BOD Load
Muni Ind. BOD Load
Sediment
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Dissolved Oxygen Conceptual Model BOD Sources,
DO Sources
Cape Fear, Black NECF BOD Load
decaying phytopl.
Surface Reaeration
Estuary Inflow BOD Load
Phytoplank. Productivity
Muni Ind. BOD Load
Ocean Inflows
MCFR Inflows
Sediment
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Dissolved Oxygen Conceptual Model BOD Sources,
DO Sources Sinks
Input of NECF Black R. Low DO Water
Cape Fear, Black NECF BOD Load
decaying phytopl.
Surface Reaeration
Estuary Inflow BOD Load
Phytoplank. Productivity
Muni Ind. BOD Load
BOD Consumption
Ocean Inflows
MCFR Inflows
Sediment
Sediment O2 Demand
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Steps in Applying a Mechanistic Model

• Decide on What to Model
• Decide on Questions to be Answered
• Choose Model
• Collect Data for Inputs, Calibration
• Create Input Files
• Create Initial Test Application
• Perform Qualitative Reality Check Calibration
  Debugging

9
Steps in Applying a Mechanistic Model, continued

• Perform quantitative calibration model
  verification
• Design model scenario testing procedure
  (endpoints, scenarios, etc.)
• Perform scenario tests
• Assess model reliability
• Document results

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Description of Model Application
Black River Flow Boundary Cond.
NE Cape Fear Flow Boundary Cond.
Cape Fear R. Flow Boundary Cond.
Lower Cape Fear River Estuary Schematic
Open Boundary Elevation Cond.
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Description of Model Application

• Flow boundary condition upstream (3 rivers)
• Elevation boundary condition downstream
• 20 lateral point sources (WWTPs)
• Extra lateral sources add water from tidal
  creeks, marshes (14 additional sources)
• 37 total freshwater sources

12
Model State Variables

• Water Properties
• Temperature, salinities
• Circulation
• Velocities, water surface elevations
• Nutrients
• Organic and inorganic nitrogen, phosphorus,
  silica
• Organic Matter
• Organic carbon (labile particulate, labile and
  refractory dissolved), phytoplankton (3 groups)
• Other
• Dissolved oxygen, total active metal, fecal
  coliform bacteria

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Water Quality Model Schematic
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Data Collected to Support Model

• Data Collected from 8 sources
• US ACoE, NC DWQ, LCFRP, US NOAA, US NWS, USGS,
  Wilmington wastewater authority, International
  Paper
• Nearly 1 TB of original data collected
• File management system created to save and
  protect original data

15
Observed Data Used to Create Model Input Files

• Meteorological forcings (from NWS)
• Freshwater inflows (from USGS)
• Elevations at Estuary mouth (from NOAA)
• Quality, temperature of freshwater inflows and at
  estuary mouth (from LCFRP, USGS, DWQ)
• Other discharges (from DWQ)

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EFDC Input Files Data Sources
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Lower Cape Fear River Program Sites Used
18
USGS Continuous Monitoring and DWQ Special Study
Stations Used
19
New Cross- Sections Surveyed by NC DWQ
20
SOD Monitoring Stations Performed by NC DWQ
21
LCFR Grid

• Channel Cells in Blue
• Wetland Cells in White
• Marsh and Swamp Forest in Green, Purple

22
LCFR Grid Characteristics

• Grid based on NOAA bathymetry and previous work
  by TetraTech
• Off-channel storage locations (wetland cells)
  based on wetland delineations done by NC DCM
• 1050 total horizontal cells (809 channel cells,
  241 wetland cells)
• 8 vertical layers for each horizontal cell
• Used a sensitivity analysis to locate and size
  wetland cells

23
Model Grid Showing Location and Size of Wetland
Cells
24
Riverine Swamps and Saltwater Marshes in Estuary
(NC DCM)
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Input File Specification

• Inflows
• Temperatures and Water Quality Concentrations at
  Boundaries
• Water quality mass loads for point sources
• Benthic fluxes
• Meteorological data

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Riverine Inflow Specification

• Flows based on USGS flow data
• Flows scaled based upon drainage area ratios
• 17 total inflows
• 3 rivers, 14 estuary sources

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Subwatersheds Draining Directly to the Estuary
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Subwatersheds Draining Directly to the Estuary
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Temperature and Concentration Specification

• 5 stations used (3 boundaries, 2 in estuary)
• Combined USGS and LCFRP data
• Point source specification tied to closest
  available data

30
Procedure for creating water quality mass load
file (WQPSL.INP)

• Used an automated procedure based upon available
  data (LCFRP, DMRs)

31
An Example Conversion Matrix (Cape Fear River
Inflow)
32
Benthic fluxes and meteorological data

• Used a prescriptive benthic flux model
• SODs time varying, but constant across estuary
• SOD values based upon monitoring data
• Met data constant across estuary
• Met data taken from Wilmington airport

33
Model Calibration and Confirmation

• 2004 calendar year used for model calibration
• Nov 1, 2003 to Jan. 1 2004 used for model startup
• 2005 calendar year used for confirmation run
  (a.k.a. verification, validation run)

34
Streamflows during Model Runs

• 2004 dry until October
• Early 2005 had some high flows
• Summer 2005 was dry

35
Hydrodynamic Model Calibration

• Examined water surface elevations, temperatures,
  salinities
• Used LCFRP and USGS data for model/data
  comparisons of salinity temperature
• Used USGS and NOAA data for model/data
  comparisons of water surface elevation
• USGS data based on pressure measurements not
  corrected for barometric changes

36
Monitoring Stations Used for Hydrodynamic
Calibration
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Simulation of Tidal Attenuation in Estuary

• Varied wetland cell widths to determine effect on
  attenuation of tidal amplitude
• Wider wetland cells gave more attenuation, as
  expected
• Also tried different distribution of wetland
  cells within estuary

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M2 Tidal Amplitude for Various Cell Width
Scenarios
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M2 Tidal Amplitude for Various Cell Distribution
Scenarios
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M2 Tidal Amplitude for Various Cell Distribution
Scenarios
Width 2, v1 chosen as best overall (in green)
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Example Time Series Comparison Black at Currie
(upstream), 2004
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Example Time Series Comparison NECF at
Wilmington, 2004
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Example Time Series Comparison Cape Fear at
Marker 12, 2004
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Example Time Series Comparison Black at Currie
(upstream), Jan. 04
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Example Time Series Comparison Wilm. Tide Gage,
Jan. 04
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Example Time Series Comparison Cape Fear at
Marker 12, Jan. 04
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Example Time Series Comparison Salinities at
Navassa, 2004
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Example Time Series Comparison Salinities at
NECF Wilm., 2004
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Example Time Series Comparison Salinities at
Marker 12, 2004
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Calibration Statistics, Salinity
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Salinity Scatter Plot
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Temperature Scatter Plot
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Calibration Statistics, Temperature
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Water Quality Calibration

• Added a second category of dissolved organic
  matter (refractory C, N, P)
• Split between labile and refractory based upon
  longer-term BOD measurements from LCFRP, IP,
  Wilmington wastewater authority
• Accounted for effects of NBOD in these tests

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Water Quality Model Schematic
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Water Quality Model Schematic
State Variables Usually Used to Simulate Organic
Matter Load
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Water Quality Model Schematic
Additional State Variables Used (settling
velocity 0.0)
State Variables Usually Used to Simulate Organic
Matter Load
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Partitioning Organic Matter into Labile and
Refractory Parts

• Fit data to 2 component model for BOD exertion,
  using equation

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Example Long-term BOD, IP discharge, 7/20/2003
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Partitioning Organic Matter into Labile and
Refractory Parts

• Fit data to 2 component model for BOD exertion,
  using equation

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Loading Breakdown for DOC
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Loading Breakdown for Refractory DOC
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Loading Breakdown for NH4
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Also implemented time variable SOD (varies w/
temperature)
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Example Time Series Comparison DO at Navassa,
2004
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Example Time Series Comparison DO at NECF
Wilm., 2004
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Example Time Series Comparison DO at Marker 12,
2004
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Calibration Statistics, DO
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DO Scatter Plot
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DO Percentile Plot
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Calibration of Other WQ Constituents

• Show some key constituents
• Ammonia, nitratenitrite, total phosphorus,
  chlorophyll-a
• Show only at Navassa (more plots in report)
• Overall, water quality model predicts each of the
  constituents well

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Example Time Series Comparison Ammonia at
Navassa, 2004
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Example Time Series Comparison NOx at Navassa,
2004
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Example Time Series Comparison TP at Navassa,
2004
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Example Time Series Comparison Chl-a at
Navassa, 2004
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Confirmation Run Results

• Ran model for calendar year 2005, with parameters
  determined from calibration
• USGS continuous monitoring data ended by then,
  used LCFRP data instead
• Show time histories only at Navassa (more in
  report)

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Example Time Series Comparison Salinities at
Navassa, 2005
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Example Time Series Comparison Temperatures at
Navassa, 2005
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Example Time Series Comparison DO at Navassa,
2005
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Model Fit Statistics, DO, 2005 Confirmation Run
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DO Percentile Plot, Predicted vs. Observed, 2005
Confirmation Run
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Sensitivity Testing

• Examined effect of varying SOD on model DO
  predictions and sensitivity of system to changes
  in organic matter loading
• SOD had an significant impact on model
  predictions
• Effect of changing SOD on effect of load changes
  shown in next section (scenario testing)

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Scenario Tests - Methods

• In general, test effect of changing wastewater
  input on water quality of system
• Changed loads only for oxygen demanding
  constituents (DOC, RDOC, Ammonia
• Examine DOs during warm weather period (April 1
  November 1) at 18 stations spread across impaired
  area
• Look at predicted DOs in each layer
• 6 scenario tests done so far

84
Six Scenario Tests Done so Far

• Changes in Flow (and load) of Brunswick Co. WWTP
• Removal of load from all WWTPs, and from 3 (IP,
  Wilm NS SS)
• Removal of Ammonia load from all WWTPs
• Increase all WWTPs to maximum permitted load
• Reduction in load from rivers, tidal creeks,
  wetlands
• Reduction in loads for various SOD values

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1. Changes in Flow (and load) of Brunswick Co.
WWTP

• Base case flow 0.38 MGD
• Three increased flows
• 4.3 times base
• 12.1 times base
• 39.1 times base

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2. Removal of load from all WWTPs, and from 3
(IP, Wilm NS SS)

• Completely removed CBOD ammonia load from all
  WWPTS
• Tried turning off just IP, just Wilm NS SS

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3. Removal of Ammonia load from all WWTPs

• Removed ammonia load from all 20 WWTP inputs
• No changes to CBOD load

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4. Increase all WWTPs to maximum permitted load

• Increased all flows and loads to maximum
  permitted values
• Assumed constant load at maximum permitted value

89
5. Reduction in load from rivers, tidal creeks,
wetlands

• Manipulated concentrations ( loads) of all 17
  freshwater inputs (3 rivers, 14 estuary sources)
• Reduced loads by 30 and 50

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6. Reduction in loads for various SOD values

• Varied SOD above and below calibrated value
• Observed effect of turning all WWTP loads off for
  each SOD case

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Summary Conclusions

• Successfully created a simulation model of
  dissolved oxygen in Lower Cape Fear River Estuary
• Model testing included calibration, confirmation,
  and sensitivity analyses
• Scenario tests used to investigate system
  sensitivity to changes in organic matter and
  ammonia load
• System found to be only moderately sensitive to
  changes in WWTP load

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Additional Work Ongoing

• Working to finalize modeling report and other
  publications
• Will work with DWQ personnel to incorporate model
  results into TMDL
• Training DWQ personnel to run LCFR model and
  analyze additional scenarios

93
Additional Work Ongoing

• Working to finalize modeling report and other
  publications
• Will work with DWQ personnel to incorporate model
  results into TMDL
• Training DWQ personnel to run LCFR model and
  analyze additional scenarios
• Questions?

94
Additional Work Ongoing

• Working to finalize modeling report and other
  publications
• Will work with DWQ personnel to incorporate model
  results into TMDL
• Training DWQ personnel to run LCFR model and
  analyze additional scenarios
• Additional analyses done that are not in report

95
Effect on DO of deepening navigation channel

• Entrance channel deepened from 40 to 44 feet
• Remainder of channel (up to CF Mem. Br.) deepened
  from 38 to 42 feet

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Effect of Changing River Load and SOD

• Considers possible cleanup of sediments
• SOD lowered by same percentages (30 and 50) as
  riverine loading

97
Analysis of DO deficit in the impaired region

• Examined summer average DOs (surface) at 3 sites
  in impaired region
• Used linear sensitivity analysis to attribute
  deficit to either WWTPs, SOD, or river loads