Estuary Eutrophication Models:
Essential Components and
Material Exchanges
By
Jim Bowen, UNC Charlotte
presented at
Multi-Media Modeling Workshop
March 23, 1999
Talk Addresses Three Questions
1. What are the Essential Components
of an Estuary Eutrophication Model?
2. What are the Cross-Media
Exchanges?
3. Which Exchanges are Important in
the Neuse River?
Common Components of Estuary
Eutrophication Models
• Based on review of existing models
• Numerical model development started
in 70’s
• All models include hydrodynamic and
water quality components
• Focus here is on the water quality
component
Define Essential Capabilities of
Model
• Predict impact of pollutant loadings
– suspended solids, nutrients, oxygen
consuming wastes (C & N),
• Common endpoints of concern
– dissolved oxygen, algal abundance
• Other endpoints may also be desired
(e.g. harmful algal blooms, fish kills,
toxic organics)
Eutro. Models - Common Components
Phytoplankton
Predation,
Mortality
Photosynthesis
Respiration
Oxygen,
Other Oxidants
Living & Non-Living
Organic Matter
Remineralization
Recycling
Nutrients
Settling, Denitrification,
Organic Matter Remineralization
Benthos
Multi-Element Components
=
Living & Non-Living
Organic Matter
=
Phytoplankton
C
N P Si
C
N
P Si
Benthos
Examples: Qual2E, WASP
Phytoplankton
1. Phyto as chl-a
Oxygen,
Other Oxidants
Living & Non-Living
Organic Matter
2. BOD
3. Org. N
4. Org. P
Nutrients
5. Dissolved Oxygen
6. NH3
7. NO2
8. NO3
9. Ortho P
Benthos
Examples: CE-Qual-W2, V3 (NEEM)
Phytoplankton
Living & Non-Living
Organic Matter
1. Diatoms, Dinoflagg’s
2. B-G Algae
3. Mixed Summer Phyto.
4. Labile Partic. OM
5. Refrac. Partic. OM
6, 7. L & R Diss. OM
8. Part. Si
Oxygen,
Other Oxidants
9. Dissolved Oxygen
Nutrients
10. NH3
12. Diss. Si
11. NO2+ NO3 13. Ortho P
14. Benthic Organic Matter
Benthos
Examples: Hydroqual, CE-Qual-ICM
Phytoplankton
1. Diatoms, Dinoflagg’s
2. B-G Algae
3. Mixed Summer Phyto.
Oxygen,
Other Oxidants
19. Dissolved Oxygen
Living & Non-Living
Organic Matter
4,5,6. Lab-Par-Org C,N,P
7,8,9. Ref-Par-Org C,N,P
10,11,12. Lab-Dis-Org C,N,P
13,14,15. Ref-Dis-Org C,N,P
16,17. Reactive, Exuded DOC
18. Biogenic Silica
Nutrients
20. NH3
22. Diss. Si
21. NO2 +NO3 23. Ortho P
24-32. React, Refr, Inert Part. C,N,P
Benthos
Divide Estuary into Segments
NEUSE ESTUARY EUTROPHICATION MODEL:
1
MODEL SEGMENTATION
1
-5
6 - 10
Upper Broad Creek
11 - 15
16 -20
New Bern
21 -25
65
64
Goose Creek
Broad Creek
63
Trent River
Arapahoe
26 30
CROATAN
NATIONAL
FOREST
61
56 - 60
31 35
36 40
51 - 55
41 - 45
46 50
South
River
Hancock
Creek
N
20 Miles
20 KM
Slocum
Creek
Cherry Point
Havelock
South River
Back Creek
Adams Creek
Clubfoot Creek
X-section Representation
• trapezoidal cross-sections for each
segment
Layer 1
S1
S2
S3
S4
S2
S3
S1
Layer 4
Sediment
Compartments
Exchanges with Other Media
Neuse Estuary
Eutrophication
Model
Physical
Processes
Modeled Salinities - September 1991
Nitrogen
Cycling
Organic Matter Phytoplankton
Nutrients
RDON
NO3
LDON
Dia-Dino
Sum. Phyto.
B-G Algae
NH4
LPON
RPON
Benthic ON
Benthos
Component Analysis - Summer 1997
• Based on the NEEM simulations
• Calibrated/Verified to 1991 and 1997
monitoring data
• Summer conditions (June - September)
Carbon Distribution by Component
0.411%
0.0209%
5.17%
0.678%
0.0374%
0.676%
46.5%
LDOM
RDOM
LPOM
RPOM
Dia-Dino
Sum. Phy.
B-G Alg.
BOD
46.5%
Benthic OC = 500%
Relative Mass
Nitrogen Distribution by Component
0.0186%
9.33%
4.61%
2%
0.604%
0.0333%
0.602%
41.4%
41.4%
Relative Mass
LDOM
RDOM
LPOM
RPOM
Dia-Dino
Sum. Phy.
B-G Alg.
NH3
NOX
Phosphorus Distribution by Component
0.0181%
14.1%
0.585%
4.46%
0.0322%
0.583%
40.1%
40.1%
Relative Mass
LDOM
RDOM
LPOM
RPOM
Dia-Dino
Sum. Phy.
B-G Alg.
PO4
Estuary Exchanges
• Looked at loadings:
– freshwater loading to estuary
– NH4 and NO3 loading to estuary
• Combines monitoring and modeling
results
• Examined June - September 1997
Estuary Loadings: Freshwater
Neuse R.
Trent R.
Weyer. WWTP
Swift Ck.
Bachelor Ck.
Precipitation
23.9%
1.05%
3.31%
1.2%
62%
8.5%
Relative Flow
Estuary Loadings: Nitrogen
0.899%
22.6%
21.3%
Riverine NH4
Riverine NOx
Precipita. NH4
Precipita. NOx
Sediment Release
Pamlico NH4
Pamlico NOx
DOM recycle
1.07%
2.24%
3.06%
18%
30.9%
Relative Amount
Summary
• All estuary eutrophication models have 4
components in common
– phytoplankton, organic matter, nutrients,
oxidants
• In Neuse, most water-column C, N, & P is
in phytoplankton pool
• Important freshwaater exchanges occur w/
Neuse & Trent R., atmosphere
• Internal recycling important to nutrient
exchange