OMSAP Public MeetingSeptember 1999

The Utility of the Bays Eutrophication Model in the Harbor Outfall Monitoring Program

James FitzpatrickHydroQual, Inc.

September 22, 1999

OMSAP Public MeetingSeptember 1999

Objectives of Water Quality Modeling

Define Cause and Effect Relationships

Define Impacts of Pollutant Sources

Assess Required Levels of Control

Evaluate Planning Alternatives for Water Quality Management

Focus Additional Monitoring and Research Needs

Assess Future Water Quality Conditions

InflowOutflow

Light

ConcernsEcologicalEcological NutrientsNutrients Contaminants Organic MaterialOrganic Material Food Chain Community Structure Living Resources

Human Health Contaminants Bacteria Viruses Bioaccumulation

SEDIMENT

Mammals

Infauna

Piscivorous Fish

Zooplankton

PhytoplanktonPhytoplankton

Planktivorous Fish

Epibenthos

Demersal Fish

RegenerationRegeneration

DetritusDetritusParticulateParticulate

MicrobesMicrobes

DissolvedDissolved

WATER COLUMN

Sources RiversRivers BoundaryBoundary Nonpoint EffluentsEffluents

Gas ExchangeExchangeN2, | O2, CO2

ATMOSPHERE

N, P, Si, ON, P, Si, O22, CO, CO22 MicrobesMicrobes

OMSAP Public MeetingSeptember 1999

BEM Model Formulation

OMSAP Public MeetingSeptember 1999

BEM Model Chlorophyll Comparison 1992-1994

Solid lines are the modeled response in Chlorophyll in the surface waters

Open circles depict monitoring results

OMSAP Public MeetingSeptember 1999

BEM Model Particulate Organic Carbon Comparison 1992-1994

Solid lines are the modeled response in POC in the surface waters

Open circles depict monitoring results

OMSAP Public MeetingSeptember 1999

October 1993

0

10

20

30

40

50

60

70

80

0.0E+00 1.0E+06 2.0E+06 3.0E+06 4.0E+06 5.0E+06 6.0E+06 7.0E+06

Asterionellopsis Glacialis (cells/L)

C/C

hla

Ra

tio

BEM Model 1993 Fall Bloom Event

Relationship among carbon, chlorophyll, and cell abundance during the Ocober 1993 Asterionellopsis Glacialis bloom

RegionalPrimary Production1993

OMSAP Public MeetingSeptember 1999

BEM Model Dissolved Oxygen Comparison 1992-1994

Solid lines are the modeled response in DO in the bottom waters

Closed circles depict monitoring results

OMSAP Public MeetingSeptember 1999

BEM Model Temperature Comparison 1992-1994

Solid lines are the modeled response in temperature

Closed circles depict bottom water monitoring results

Open circles depict surface water monitoring results

OMSAP Public MeetingSeptember 1999

BEM Model Salinity Comparison 1992-1993

Solid lines are the modeled response in salinity

Closed circles depict bottom water monitoring results

Open circles depict surface water monitoring results

OMSAP Public MeetingSeptember 1999

BEM Model DIN Comparison 1992-1994

Solid lines are the modeled DIN response

Open circles depict surface water monitoring results

OMSAP Public MeetingSeptember 1999

BEM Model Sediment Oxygen Demand 1992-1994

Solid lines are the modeled SOD at selected locations in Massachusetts Bay

Closed circles depict monitoring results

OMSAP Public MeetingSeptember 1999

BEM Model Mass Balance Capability

OMSAP Public MeetingSeptember 1999

BEM Model Nitrogen Mass Balance

OMSAP Public MeetingSeptember 1999

BEM Model Effluent Influence Total Nitrogen - Deer Island

Total N concentration (solid lines) resulting from the boundary condition and effluent discharged from Deer Island and fraction contribution (dashed line) of MWRA effluent at various locations within Massachusetts Bay.

OMSAP Public MeetingSeptember 1999

BEM Model Effluent Influence Total Nitrogen - Mass Bay Outfall

Projected total nitrogen concentration (solid lines) resulting from the boundary condition and effluent discharged from Deer Island and fraction contribution (dashed line) of MWRA effluent at various locations within Massachusetts Bay.

OMSAP Public MeetingSeptember 1999

BEM Model Predictive Capability

Distribution chlorophyll in surface waters under two nutrient loading regimes

COL = Current outfall locationFOL = Future outfall location

OMSAP Public MeetingSeptember 1999

the spatial decrease in phytoplankton biomass in Mass Bay as a function of distance from Boston Harbor

the limitation of the winter/spring diatom bloom in Cape Cod Bay by silica

the limitation of summer primary productivity by DIN the annual cycle of primary productivity in northwest Mass

Bay the annual cycle of DO, with minimum bottom water

concentrations occurring in late September and October

The BEM appears to capture a number of spatial and temporal features of water quality within the Bays during the 1992-1994 time

period, including:

BEM Model Compatibility to Measured Responses

OMSAP Public MeetingSeptember 1999

The Asterionellopsis glacialis bloom observed in the fall of 1993,• however, estimates of the magnitude of the bloom may be

exaggerated due to low C:Chl-a ratios observed in the A. glacialis

the minimum DO concentrations in the fall of 1994,• however, the model was able to compute minimum DO

concentrations that were approximately 1 mg/L lower in the fall of 1994 as compared to 1992 and 1993

The BEM was not able to fully reproduce two of the unique features of the 1992-1994 data set:

BEM Model Limitations

OMSAP Public MeetingSeptember 1999

BEM is able to reproduce a number of the spatial and temporal features of water quality observed in the 1992-1994 HOM data sets

BEM provides a tool with which to assess the relative importance of various nutrient inputs to the Mass Bays system

BEM provides a tool with which to assess the spatial and temporal effects of outfall relocation and increased nutrient inputs on primary productivity within the Mass Bays system

BEM can also suggest where additional monitoring and field studies need to be performed (e.g., open water boundaries and benthic primary productivity

BEM Model Utility