Progress Report
of the
Baywide Nutrient
Reduction Reevaluation
Chesapeake
Bay
Program
Chesapeake
fe Bay
^ Program
-------
Progress Report
of the
Baywide Nutrient
Reduction Reevaluation
February 1992
Printed by the U.S. Environmental Protection Agency for the Chesapeake Bay Program
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FOREWORD
The Chesapeake Bay Program is the ongoing Bay restoration program conducted
jointly by the District of Columbia, Virginia, Pennsylvania, Maryland, the Chesa-
peake Bay Commission, the U.S. Environmental Protection Agency, and other
federal agencies.
In 1987, the parties to the original Chesapeake Bay Agreement of 1983 signed
a new Chesapeake Bay Agreement. The 1987 Chesapeake Bay Agreement set
a specific goal—to achieve at least a 40 percent reduction of nitrogen and
phosphorus entering the mainstem Chesapeake Bay by the year 2000. The
agreement also included a provision that the goal be reevaluated in 1991 to
determine whether it is, indeed, the reduction needed.
The ecological balances in the Bay are extremely complex and are affected by
many factors. Nutrient enrichment is just one of the important factors contributing
to imbalances in the Bay's delicate ecology. The purpose of this progress report
is to give an overview of the problem caused by excess nutrients in the Bay, to
explain the status of the ongoing Nutrient Reduction Reevaluation, and to report
progress to date. Remarkable progress is being made in reducing nutrient
discharges within the Chesapeake Bay basin. This has been reflected in positive
trends in water quality and in the return of underwater grasses to some of the
Bay's shorelines. Strides have been made in pollution control in both the public
and private sectors.
A number of tools are being used to determine the validity of the goal and the
effects the nutrient reduction will have on the Bay's water quality: (1) computer
models are being used to guide the reevaluation; (2) research, monitoring and
detailed studies of the habitat requirements of the Bay's living resources (plant
and animal life) are being conducted; (3) engineering studies of control options
for managing point and nonpoint source pollution are underway.
Although this progress report's findings are preliminary, trends and generaliza-
tions of nutrient loads, water quality, and habitat improvements are becoming
evident. Most of the background studies for the Nutrient Reduction Reevaluation
have been drafted. To date, seven model runs have been completed for use in
this report. Many additional computer model runs and refinements of the model
will be necessary before results can be synthesized into final recommendations.
This reevaluation has been supported by many Chesapeake Bay Program par-
ticipants who have worked since the original Baywide Nutrient Reduction
Strategy was prepared in 1988. This report was prepared by a Reevaluation
Workgroup whose members are noted on the next page. We look forward to
presenting our final report later this year.
Robert Perciasepe
Chairman
Nutrient Reevaluation Workgroup
CSC.IR18.1V91
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ACKNOWLEDGMENTS
THE NUTRIENT REEVALUATION WORKGROUP:
Robert Perciasepe
Reeval.uation Workgroup Chairperson,
Maryland Secretary of the Environment
Lou Bercheni
Pennsylvania Department of Environmental
Resources
Edwina Coder
Chairperson Citizens Advisory Committee
James Collier
Chairperson Modeling Subcommittee, District
of Columbia Consumer and Regulatory Affairs
James Cox
Chairperson Nutrient Reduction Task Force,
Virginia Department of Conservation and
Recreation
Michael Haire
Maryland Department of the Environment
Verna E. Harrison
Chairperson Living Resources Subcommittee,
Maryland Department of Natural Resources
Michael Hirshfield
Citizens Advisory Committee representative,
Chesapeake Bay Foundation
Veronica Kasi
Pennsylvania Department of Environmental
Resources
Kenneth Laden
District of Columbia Department of Public
Works, Office of Policy & Planning
Joseph Mihursky
Chairperson Scientific and Technical Advisory
Committee
Larry Minock
Virginia Council on the Environment
Alan Pollock
Virginia State Water Control Board
Rosemary Roswell
Chairperson Nonpoint Source Subcommittee,
Maryland Department of Agriculture
Charles S. Spooner
U.S. Environmental Protection Agency
Chesapeake Bay Program Office
Ann Pesiri Swanson
Chesapeake Bay Commission
Cameron Wiegand and James Shell
Local Government Advisory Committee
representative, Montgomery County
Lee Zeni
Chairperson Monitoring Subcommittee,
Interstate Commission on the Potomac River
Basin
The Nutrient Reevaluation Workgroup coordi-
nated its efforts with many other Chesapeake
Bay Program participants including the Mod-
eling Subcommittee, the Nutrient Reduction
Task Force, the Living Resources Subcommit-
tee, the U.S. Army Corps of Engineers—
Baltimore District and Waterways Experi-
ment Station. This effort benefited from the
services of a number of respected consultants
and public agencies including Computer Sci-
ences Corporation and their consultant Dr.
Robert V. Thomann, Aqua-Terra, Hydroqual,
the U.S. Environmental Protection Agency,
and the Model Evaluation Group.
Thil document wai produced by Computer Science! Corporation for U.S. Environmental Protection Agency Contract No. 68-WO-0043
^ CSC.LR1B12/91
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TABLE OF CONTENTS
FOREWORD i
ACKNOWLEDGMENTS iii
Chapter 1: THE PROBLEM AND THE STRATEGY 1
Identifying the Problem 1
The Chesapeake Bay Agreements 3
The Baywide Nutrient Reduction Strategy 4
Chapter 2: PROGRESS TO DATE 5
Nutrient Load Inventories 5
Progress In Chesapeake Bay Nutrient Control 12
Water Quality Trends and Characterization 16
Chapter 3: THE REE VALUATION 21
Major Objectives of the Reevaluation 22
Water Quality and Living Resource Objectives 23
Modeling. Efforts 25
Technology Effectiveness and the
Costs of Nutrient Load Reductions 30
Chapter 4: FINDINGS & FUTURE ACTIVITIES 33
Findings 33
Future Activities 35
TECHNICAL APPENDIX 37
Water Quality and Living Resource Objectives 37
Model Refinements 44
Technology Effectiveness and Cost
for Nutrient Load Reductions 54
Process and Approach 55
GLOSSARY 59
REFERENCES 65
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Chapter 1: The Problem and the Strategy
THE PROBLEM AND THE STRATEGY
Identifying the Problem
In the mid-1900s, scientists, government officials and concerned citizens
realized that the Chesapeake Bay was in trouble. Studies completed in the
1970s substantiated that increases in agricultural development, population
growth, and sewage treatment plant flows were causing the Bay to become
nutrient enriched (Figure 1). This condition involves a chain reaction. High
levels of nutrients (primarily phosphorus and nitrogen) flow into the Bay's
waters causing excessive algal growth. When the algae die and fall to the
Bay's bottom, they are decomposed by bacteria which deplete the water's
oxygen supply, particularly near the bottom where much of the Bay's aquatic
life lives.
EFFECTS OF POLLUTANTS IN THE BAY
HEALTHY SYSTEM NUTRIENTS SEDIMENTS TOXICANTS
ALGAL BLOOMS
HUMAN HEALTH
CONCERNS
LOW DISSOLVED
OXYGEN
WATER COLUMN HABITAT
• Clear water
Algal growth balanced
Oxygen levels adequate
Finfish abundant
FOOD CHAIN
EFFECTS
4
POOR WATER CLARITY
AQUATIC PLANT HABITAT
FLOURISHES
AQUATIC PLANT
GROWTH INHIBITED
FISH, SHELLFISH AND OTHER
ORGANISMS STRESSED
BOTTOM HABITAT
HEALTHY
Figure 1. Effects of pollutants in the Bay (Source: Maryland Department of the Environment)
1
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Progress Report of the Baywide Nutrient Reduction Reevaluation
Although problems other than nutrient enrichment existed in the B ay (e. gtox ics
and overfishing), their extent was unclear. Nutrient enrichment, however, was
relatively well understood. It was also understood that no individual category
of nutrient sources was to blame for the excess nutrients and that no single state
bordering the Bay could solve the problem by itself—meeting the challenge would
involve a regional effort (Figure 2).
Through a series of formal agreements in 1983 and 1987, the jurisdictions
bordering the Bay—Pennsylvania, Maryland, District of Columbia, and Vir-
ginia—along with the Chesapeake Bay Commission and the U.S. Environmental
Protection Agency (EPA), agreed to develop a cooperative strategy to deal with
nutrient enrichment and other Bay ecological problems.
Chesapeake Bay Watershed
WVA
Figure 2. The Chesapeake Bay is the largest estuary in the contiguous United States. The Bay itself is part of an
interconnected system which includes the mouths of many rivers draining parts of New York, Pennsylvania, West
Virginia, Maryland, Delaware, Virginia and the District of Columbia. The Bay and all of its tidal tributaries comprise
the Chesapeake Bay ecosystem. (Text Source: Chesapeake Bay: Introduction to an Ecosystem; Graphic Source:
Chesapeake Bay Barometer, December 1991 issue, Chesapeake Bay Program)
CSC.LK1B.1M1
2
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Chapter 1: The Problem and the Strategy
The Chesapeake Bay Agreements
Much of the success of the Chesapeake Bay Program has resulted from the
cooperative strategies developed by the participating jurisdictions and the EPA.
Fundamental to this cooperative spirit has been the convening of two major
Chesapeake Bay conferences and the signing of two landmark Chesapeake Bay
Agreements.
1983 Agreement
The major environmental problems of the Chesapeake Bay and its tributaries were
investigated in a comprehensive study initiated in 1975 by the EPA at the direction
of Congress. In September 1983, final research findings and recommended
remedial strategies were published identifying ten areas of environmental con-
cern.12 Three specific concerns were targeted for concentrated examination:
nutrient enrichment, toxic substances, and the decline in submerged aquatic
vegetation.
The Chesapeake Bay Agreement of December 19833, signed by Maryland,
Virginia, Pennsylvania, the District of Columbia, the Chesapeake Bay Commis-
sion and the EPA, established the major elements of a cooperative structure to
develop and coordinate a comprehensive Bay restoration and protection program.
These elements included the Chesapeake Executive Council, the Implementation
Committee, and the EPA Chesapeake Bay Program Office.
1987 Agreement
In December 1987, the signatories to the 1983 Agreement signed a new Bay
Agreement.'1 It significantly expanded the original pact by listing specific goals,
objectives, and commitments in six categories including water quality. The water
quality goal is to "reduce and control point and nonpoint sources of pollution
to attain the water quality condition necessary to support the living resources of
the Bay."
The agreement specifically required the signatory jurisdictions:
"By July 1988, to develop, adopt, and begin implementation of a basinwide
strategy to equitably achieve by the year 2000 at least a 40% reduction of nitrogen
and phosphorus entering the mainstem of the Chesapeake Bay. The strategy
should be based on agreed upon 1985 point source loads and on nonpoint loads
in an average rainfall year," and, "by December 1991, to reevaluate the 40 percent
reduction target based on the results of modeling, research, monitoring and other
information available at that time."
3
C8C.LR1B.I2/01
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Progress Report of the Baywide Nutrient Reduction Reevaluation
The Baywide Nutrient Reduction Strategy
During the period between the 1983 and 1987 Chesapeake Bay Agreements, the
Bay Program developed a relatively simple mathematical model that was used
to devise a strategy for reducing the amount of nitrogen and phosphorus entering
the Bay. This model evaluated the water quality response of the Bay to a variety
of nutrient reduction scenarios. The model's results predicted that if nutrient loads
were reduced 40%, nutrient enrichment would be reduced sufficiently to stop the
depletion of dissolved oxygen (particularly in the deep, central region of the Bay),
thereby encouraging the recovery of the Bay's living resources to earlier, higher
population levels.
In July 1988, the Chesapeake Executive Council adopted the Baywide Nutrient
Reduction Strategy to implement the agreement's goal. The strategy:
1. documented the estimate of the 1985 "baseline" loading conditions and set
the year 2000 loading goals for nitrogen and phosphorus;
2. described the information needed over the next several years to more accu-
rately measure progress and to refine the Baywide Nutrient Reduction
Strategy to meet the year 2000 target; and,
3. defined the following phases:
Phase I: From the baseline loading year of 1985 to the 1988 adoption of
the Baywide Nutrient Reduction Strategy—during this period, significant
nutrient reductions occurred. These reductions need to be accounted for in
assessing the 40% reduction goal.
Phase 11: From 1988 to the 1991 Reevaluation—this phase allowed the
jurisdictions to project progress to the time when the reevaluation was to
occur.
Phase III: From 1991 to the year 2000—this period follows any mid-course
adjustments resulting from the 1991 Reevaluation.
C8C.LR1B.12/91
4
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Chapter 2: Progress to Date
PROGRESS TO DATE
Progress, for the purposes of this report, is documented for Phases I and II of
the Baywide Nutrient Reduction Strategy commencing with the baseline year
1985 through the onset of the Nutrient Reduction Reevaluation. The nutrient
loads are inventoried, point and nonpoint source reductions since 1985 are noted,
and recently observed water quality trends are assessed.
Nutrient Load Inventories
Nutrients that enter the Chesapeake Bay originate from point sources (e.g.,
municipal and industrial wastewater discharge), nonpoint sources (e.g., cropland,
animal wastes, urban and suburban runoff), and from atmospheric deposition
(airborne contaminants). These sources span so vast an area that it is difficult
to collect comprehensive data throughout the watershed. Therefore, a computer
simulation of sources was used as the common mechanism for estimating both
the 1985 base load, and the load reductions that are feasible by the year 2000.
The 40% nutrient reduction is computed on loads estimated for a base year, chosen
to be 1985. In 1987, when the Baywide Nutrient Reduction Strategy was devised,
considerable uncertainty surrounded loading estimates. Work was begun almost
immediately to collect data and inventory point and nonpoint source loadings
to determine a more precise benchmark as the starting point for reductions.
Updated point source loadings were provided by the four jurisdictions: Maryland,
Virginia, Pennsylvania, and the District of Columbia. The 1991 version of the
Chesapeake Bay Watershed Model was used to revise an estimate of the average
nonpoint source loads of 1985.
The 1985 base nonpoint source load estimate for this reevaluation is derived from
the output of the Watershed Model averaged for the period 1984-87, which
represents a range of river flow conditions. An average of four years is used
because nonpoint source nutrient loads are largely a function of natural variations
in runoff and river flow. This period was thought to approximate long-term
average conditions. Figures 3a and 3b show the distribution of sources presently
being considered in the reevaluation. Nonpoint sources continue to be dominant
sources of both nutrients, but point sources are also significant. Atmospheric
deposition (both wet and dry) is shown as a contribution to water surfaces, but
is otherwise considered in this report to be a contribution to nonpoint source loads.
Further work is needed to determine what portion of the sources shown as
nonpoint sources can actually be attributed to atmospheric deposition.
The goal as stated in the Agreement was to reduce nutrient loads to the Bay by
40%. The original Baywide Nutrient Reduction Strategy defined "controllable
loads" as the basis for this reduction. As a result, the Baywide Nutrient Reduction
Strategy seeks a 40% reduction in controllable loads in the states party to the
Chesapeake Bay Agreement. The "controllable" loads were originally defined
as the nutrient loads that were not natural background loads. Controllable loads
include point source and nonpoint source, and are all man-made. They were
5
CSC.LMB.12/ftf
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Progress Report of the Baywide Nutrient Reduction Reevaluation
Chesapeake Bay Basin Total Nitrogen
1985 Base Load Distribution By Load Type
Atmospheric Deposition to Tidal Bay (9.2%)
Point Source (23.1%)
Nonpoint Source (67.7%)
Total Load ¦ 376
Pounds
Figure 3a. Chesapeake Bay Ba-
sin Total Nitrogen 1985 Base Load
Distribution By Load Type (Source:
1991 Watershed Model)
Figure 3b. Chesapeake Bay Ba-
sin Total Phosphorus 1985 Base
Load Distribution By Load Type
(Source: 1991 Watershed Model)
Chesapeake Bay Basin Total Phosphorus
1985 Base Load Distribution By Load Type
Atmospheric Deposition to Tidal Bay (5.4%)
Point Source (33.7%)
Nonpoint Source (60.9%)
Total Load « 27 Million Pounds
computed as the difference between the 1985 base load and the load estimated
under 100% forest cover in the Bay watershed. In developing the original
Baywide Nutrient Reduction Strategy, each jurisdiction estimated its point source
and nonpoint source loads. Different approaches were used. Now, however,
controllable loads are calculated using uniform assumptions and are shown in
Tables la and lb for nitrogen and phosphorus, respectively, for each participating
jurisdiction and for the total area of the Chesapeake Bay watershed.5 Importantly,
80% of the nitrogen (Table la, A15+A22) and 86% of the phosphorus (Table lb,
A15+A22) come from point and nonpoint sources in the states that are party to
the Chesapeake Bay Agreement.
These nutrient loads are displayed by the states in which they originate in Figure
4a and 4b and in Tables la and lb.
CSC.LmB.t2/91
6
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Chapter 2: Progress to Date
Chesapeake Bay Basin Total Nitrogen
1985 Base Load Distribution By State
Pennsylvania (32.7%
Maryland (20.2%)
Atmospheric Deposition to Tidal Bay (9.2%)
Non Agreement States (10.7%)
District of Columbia (2.3%)
Virginia (25.0%)
Total Load . J7S Million Pounds
Figure 5a. Chesapeake Bay Basin
Total Nitrogen 1985 Base Load
Distribution By Tributary (Source:
1991 Watershed Model) (
Figure 4a. Chesapeake Bay Basin
Total Nitrogen 1985 Base Load Dis-
tribution By State (Source: 1991
Watershed Model)
Figure 4b. Chesapeake Bay Basin
Total Phosphorus 1985 Base Load
Distribution By State (Source: 1991
Watershed Model) |
Chesapeake Bay Basin Total Phosphorus 1985 Base
Load Distribution By State
Pennsylvania (23.9%)
Maryland (21.7%)
Chesapeake Bay Basin Total Nitrogen
1985 Base Load Distribution By Tributary
Atmospheric Deposition to Tidal Bay (9.2%)
Eastern Shore VA (0.5%)
Eastern Shore MD (7.3%)
Susquehanna (36.8%)
/\ Western Shore MD (7.2%)
J James (11.6%)
Patuxent (1.3%)
\VYork(1.7%)
Rappahannock (2.7%)
Potomac (21.1%)
Total Load • 37S Million Pounds
Atmospheric Deposition to Tidal Bay (5.4%)
Non Agreement States (8.2%)
District of Columbia (0.4%)
These loads are also displayed to show
the tributaries that convey them to the
Bay as in Figure 5a and 5b and Table 2a
and 2b.
These new estimates of controllable ni-
trogen loads have been reduced 9% from
1988 estimates while controllable phos-
phorus loads have been reestimated to
be 9% higher than in 1988.5
Virginia (40.3%)
Total Load • 27 MIIHon Pounds
Figure 5b. Chesapeake Bay Basin
Total Phosphorus 1985 Base Load
Distribution By Tributary (Source:
1991 Watershed Model) i
Susquehanna (24.2%)
Patuxent (1.9%)
Potomac (22.8%)
Chesapeake Bay Basin Total
Phosphorus 1985 Base Load
Distribution By Tributary
Atmospheric Deposition to Tidal Bay (5.4%)
Eastern Shore VA (0.3%)
Eastern Shore MO (8.1%)
Western Shore MD (6.7%)
Appomattox (1.0%)
James (22.6%)
York (3.4%)
Rappahannock (3.6%)
Total Load ¦ 27 WWon Pounds
csc.irib.imi
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Progress Report of the Baywide Nutrient Reduction Reevaluation
Table 1a. Nitrogen Loading to Chesapeake Bay — 1985 Base Load and Controllable Fraction (million lbs./yr),
Jurisdiction
Nutrient
Source.,
1985
Base
Load3
Forest
Background
Load4
Controllable
Load,
Controllable
Load as a %
of Base Load
Y
Axis
Pennsylvania
Nonpoint
112.4
73.8
38.6
34
1
Point
10.5
0.0
10.5
100
2
SUBTOTAL
122.9
73.8
49.1
40
3
Maryland
Nonpoint
45.5
25.2
20.3
45
4
Point
30.5
0.0
30 5
100
5
SUBTOTAL
76.0
25.2
50.8
67
6
Virginia
Nonpoint
59.5
27.2
.
32.3
54
7
Point
34.4
0.0
34.4
100
8
SUBTOTAL
93.9
27.2
66.7
71
9
District of
Columbia
Nonpoint
0.3
0.1
0.2
67
10
Point
8.5
0.0
8.5
|iri (
100
11
SUBTOTAL
8.8
0.1
8.7
99
12
Bay Agreement
Participants
Nonpoint
217.7
126.3
91.4
42
13
Point
83.9
0.0
83.9
100
14
TOTAL
301.6
126.3
175.3
58
15
Other States in
the Watershed
(NY, WV & DE)
Nonpoint
37.3
8.7
28.6
77
16
Point
2.8
0.0
2.8
100
17
TOTAL
40.1
8.7
31.4
78
18
Watershed Total
Nonpoint
255.0
135.0
120.0
47
19
Point
86.7
0.0
86.7
100
20
Atmospheric
Deposition,
34.6
34.6
0.0
0
21
TOTAL
376.3
169.6
206.7
55
22
X Axis
A
B
c
D
Source: 1991 Watershed Model Note: Shaded column shows loads thai wt»= ",ul me calculation of the 40% reduction. X/Y Axis references text
percentage sources.
1. This table is preliminary and subject to revision in the final report I source loads a
2. Nonpoint source loads include atmospheric deposition to the land. Poin ^ re reported as delivered to tidal waters.
3.1985 Base Load is 1984-87 averaged output tram the Watershed Mo j^hnicai ^ discharged below fall line.
4. Forest Background Load simulated all land uses converted to tofWM. (q contfo| JWndix: Simulation Forest Reference No. t and 2A) Includes
atmospheric deposition on the land, rivers and lakes that may be po» . (a|| ,ores «oons seen in sources originating in other states in the watershed
(lines 16-18) are attributed to their removal during transport in more n verine systems.
5. Controllable Load is Base Load minus Forest Background Load. aj0rity of this load is
6. Deposition to tidal waters only. Technical studies show that a large m attributable to man's activities, but that fraction is not estimated here.
8
CSC.LR1B.12/91
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Chapter 2: Progress to Date
Table 1 b. Phosphorus Loading to Chesapeake Bay—1985 Base Load and Controllable Fraction (million IbsJyr),
Jurisdiction
Nutrient
Source^
1985
Base
Load3
Forest
Background
Load4
Controllable
Load,
Controllable
Load as a %
of Base Load
Y
Axis
Pennsylvania
Nonpoint
4.88
0.96
3.92
80
1
Point
1.64
0.0
1.64
100
2
SUBTOTAL
6.52
0.96
5.56
85
3
Maryland
Nonpoint
3.70
1.33
2.37
64
4
Point
2.20
0.0
2.20
100
5
SUBTOTAL
5.90
1.33
4.57
77
6
Virginia
Nonpoint
6.20
2.01
4.19
68
7
Point
4.78
0.0
4.78
100
8
SUBTOTAL
10.98
2.01
8.97
82
9
District of
Columbia
Nonpoint
0.019
0.002
0.017
89
10
Point
0.107
0.000
0.107
100
11
SUBTOTAL
0.126
0.002
0.124
98
12
Bay Agreement
Participants
Nonpoint
14.80
4.30
10.50
71
13
Point
8.73
0.0
8.73
100
14
TOTAL
23.53
4.30
19.23
82
15
Other States in
the Watershed
(NY, WV & DE)
Nonpoint
1.82
0.08
1.74
97
16
Point
0.43
0.0
0.43
100
17
TOTAL
2.25
0.08
2.17
96
18
Watershed Total
Nonpoint
16.62
4.38
12.24
73
19
Point
9.16
0.0
9.16
100
20
Atmospheric
Deposition,
1.47
1.47
0.0
0
21
TOTAL
27.25
5.85
21.4
78
22
X Axis
A
B
c
D
Source: 1991 Watershed Model Note: Shaded column shows loads thai were the basis for the calculation of the 40% reduction. X/Y Axis references text
percentage sources.
1. This table is preliminary and subject to revision in the final report.
2. Nonpoint source loads include atmospheric deposition to the land. Point source loads are reported as delivered to tidal waters.
3.1985 Base Load is 1984-87 averaged output from the Watershed Model plus point source load discharged below fall line.
4. Forest Background Load simulated all land uses converted to forest. (See Technical Appendix: Simulation Forest Reference No. 1 and 2A) Includes
atmospheric deposition on the land, rivers and lakes that may be possible to control. Reductions seen in sources originating in other states in the watershed
(lines 16-18) are attributed to their removal during transport in more natural (all forested) riverine systems.
5. Controllable Load is Base Load minus Forest Background Load.
6. Deposition to tidal waters only. Technical studies show that a large majority ol this load is attributable to man's activities, but that fraction is not estimated here.
9
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Progress Report of the Baywide Nutrient Reduction Reevaluation
Table 2a. Total Nitrogen Loading to Chesapeake Bay by Major Tributary (in millions Ibs/yr),
River
Basin
Nutrient
Source.,
1985
Base
Load3
Forest
Background
Load4
Controllable
Load6
Controllable
Load as a %
of Base Load
Y
Axis
Susquehanna
Nonpoint
126.3
89.5
36.8
29
1
Point
12.4
2.6
9.8
79
2
SUBTOTAL
138.7
92.1
46.6
34
3
Patuxent
Nonpoint
3.6
1.29
2.31
64
4
Point
1.4
0.0
1.4
100
5
SUBTOTAL
5.0
1.29
3.71
74
6
Potomac
Nonpoint
53.0
38.0
15.0
28
7
Point
26.6
0.2
26.4
99
8
SUBTOTAL
79.6
38.2
41.4
52
9
Rappahannock
Nonpoint
9.7
2.4
7.3
75
10
Point
0.4
0.0
0.4
100
11
SUBTOTAL
10.1
2.4
7.7
76
12
York
Nonpoint
5.1
1.6
3.5
69
13
Point
1.3
0.0
1.3
100
14
SUBTOTAL
6.4
1.6
4.8
75
15
James
Nonpoint
21.0
8.88
12.7
58
16
Point
22.8
0.02
23.5
99
17
SUBTOTAL
43.8
8.9
36.2
80
18
Appomattox
Nonpoint
1.9
0.5
1.4
74
19
Point
0.0
0.0
0.0
—
20
SUBTOTAL
1.9
0.5
1.4
74
21
Western Shore
Maryland
Nonpoint
6.6
2.2
4.4
67
22
Point
20.5
0.0
20.5
100
23
SUBTOTAL
27.1
2.2
24.9
92
24
Eastern Shore
Maryland
Nonpoint
26.7
12.31
14.39
54
25
Point
0.9
0.09
0.81
90
26
SUBTOTAL
27.6
12.40
15.20
55
27
Eastern Shore
Virginia
Nonpoint
1.4
1.4
0.0
0
28
Point
0.3
0.00
0.3
100
29
SUBTOTAL
1.7
1.4
0.3
18
30
Watershed Total
Nonpoint
255.3
158.08
97.22
38
31
Point
86.6
2.91
83.69
97
32
Atmospheric
Deposition6
34.6
34.6
0.0
0
33
TOTAL
376.5
195.59
180.91
48
34
X Axis
A
B
c
D
Source: 1991 Watershed Model Note: Shaded column shows loads that were the basis lor the calculation of the 40% reduction. X/Y Axis references text percentage sources
1. This table is preliminary and subject to revision in the final report.
2. Nonpoinl source loads include atmospheric deposition to the land. Point source loads are reported as delivered to tidal waters
3. 1985 Base Load is 1984-87 averaged output from the watershed model plus point source load discharged below tall line.
4. Fofest Background Load simulated all land uses converted to forest (See Technical Appendix: Simulation Forest Ref. No. 1 and 2A) Includes atmospheric deposition on the land
rivers and lakes that may be possible to control.
5. Controllable Load is Base Load minus Forest Background Load.
6. Deposition to tidal waters only. Technical studies show thai a large majority of this load is attributable to man's activities, but that fraction is not estimated here
CSC.Lft1B.12/91
10
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Chapter 2: Progress to Date
Table 2b. Total Phosphorus Loading to Chesapeake Bay by Major Tributary (in millions Ibs/yr),
River
Basin
Nutrient
Source,
1985
Base
Load3
Forest
Background
Load4
Controllable
Load6
Controllable
Load as a %
of Base Load
Y
Axis
Susquehanna
Nonpoint
4.79
0.94
3.85
80
1
Point
1.80
0.17
1.63
91
2
SUBTOTAL
6.59
1.11
5.48
83
3
Patuxent
Nonpoint
0.30
0.03
0.27
90
4
Point
0.21
0.00
0.21
100
5
SUBTOTAL
0.51
0.03
0.48
94
6
Potomac
Nonpoint
4.93
2.63
2.30
47
7
Point
1.28
0.07
1.21
95
8
SUBTOTAL
6.21
2.70
3.51
57
9
Rappahannock
Nonpoint
0.83
0.08
0.75
90
10
Point
0.16
0.00
0.16
100
11
SUBTOTAL
0.99
0.08
0.91
92
12
York
Nonpoint
0.51
0.07
0.44
86
13
Point
0.43
0.00
0.43
100
14
SUBTOTAL
0.94
0.07
0.87
93
15
James
Nonpoint
2.51
0.89
1.62
65
16
Point
3.64
0.01
3.63
100
17
SUBTOTAL
6.15
0.90
5,25
85
18
Appomattox
Nonpoint
0.28
0.02
0.26
93
19
Point
0.0
0.0
0.0
—
20
SUBTOTAL
0.28
0.02
0.26
93
21
Western Shore
Maryland
Nonpoint
0.53
0.03
0.50
94
22
Point
1.29
0.00
1.29
100
23
SUBTOTAL
1.82
0.03
1.79
98
24
Eastern Shore
Maryland
Nonpoint
1.88
0.46
1.42
76
25
Point
0.34
0.04
0.30
88
26
SUBTOTAL
2.22
0.50
1.72
77
27
Eastern Shore
Virginia
Nonpoint
0.082
0.08
0.002
2
28
Point
0.003
0.0
0.003
—
29
SUBTOTAL
0.085
0.08
0.005
6
30
Watershed Total
Nonpoint
16.64
5.23
11.41
69
31
Point
9.15
0.29
8.86
97
32
Atmospheric
Deposition6
1.47
1.47
0.00
0
33
TOTAL
27.26
6.99
20.27
74
34
X Axis
A
B
C
D
Source: 1991 Watershed Model Note: Shaded column shows loads that were the basis lor the calculation ol the 40% reduction. X/Y Axis references text percentage sources
1. This table is preliminary and subject to revision in the final report.
2. Nonpoint source loads include atmospheric deposition to the land. Point source loads are repotted as delivered to tidal waters.
3. 1965 Base Load is 1984-67 averaged output Irom the watershed model plus point source load discharged below fall line.
4. Forest Background Load simulated all land uses converted to forest. (See Technical Appendix: Simulation Forest Ret. No. 1 and 2A) Includes atmospheric deposition on the land,
rivers and lakes that may be possible to control.
5. Controllable Load is Base Load minus Forest Background Load.
6. Deposition to tidal waters only. Technical studies show that a large majority of this load is attributable to man's activities, but that fraction is not estimated here.
11
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Progress Report of the Baywide Nutrient Reduction Reevaluation
Progress In Chesapeake Bay Nutrient Control
Point Source Nutrient Reductions
Point sources account for 23% of the nitrogen (Table 1 a, A20+A22) and 34% of the
phosphorus (Table lb, A20+A22) entering the Bay; municipal wastewater dis-
charges contribute the majority of these loads. Three critical elements of the
Chesapeake Bay Program's point source control strategy are responsible for these
reductions:
1. prohibiting the sale of detergents containing phosphorus, and other pollution
prevention actions;
2. upgrading wastewater treatment plants; and,
3. improving compliance with permit requirements.
A phosphorus ban limits the amount of phosphorus used in detergents and other
cleaning products to trace amounts. Because the ban reduces the amount of
phosphorus coming into wastewater treatment plants, it further reduces the amount
of phosphorus discharged into the Bay by secondary treatment plants (which do not
contain phosphorus removal systems). At advanced treatment plants which are
required to remove phosphorus to a specified level, the phosphorus ban reduces
operating costs for sludge disposal and chemical precipitants.
In Maryland the ban was implemented in late 1985 as part of Phase 1 of the nutrient
reduction program. The state has experienced a 30% decrease in influent phospho-
rus concentrations and a 16% decrease in discharged municipal phosphorus loads.
At the twenty-one advanced treatment plants in the state required to remove
phosphorus, sludge production has been reduced by 28 dry tons/day, with an annual
savings of $4.4 million realized because of the reduced need for chemical precipi-
tants.9
The District of Columbia operates the watershed's largest wastewater treatment
plant, Blue Plains. The District implemented its ban in 1986 and has experienced
a 26% decrease in influent phosphorus concentrations, a 30% decrease in chemical
usage10 and a 14% decrease in sludge volume providing an annual savings of $6.5
million (representing about 10% of the Blue Plains operating budget).
The Virginia ban was initiated in 1988. Since that time, municipal treatment plants
in Virginia have experienced a 34% decrease in influent and a 50% decrease in
effluent phosphorus concentrations. As a result, the phosphorus loads from
municipal wastewater treatment plants decreased by 46% between 1985 and 1989
despite a 13% increase in wastewater requiring treatment."
Pennsylvania implemented a phosphorus ban within the Susquehanna River basin
in 1990, and benefits are expected to be similar to those of the other jurisdictions.
The ban on phosphates used in laundry detergents eliminated between one-quarter
and one-third the total amount of phosphorus entering municipal treatment plants.
CSCLR1B.12/91
12
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Chapter 2: Progress to Date
Nitrogen reduction progress has recently begun to keep pace with the goals
established in the Baywide Nutrient Reduction Strategy.6 Improved pollution
prevention by industry and improved wastewater treatment is now reducing this
load, where in the past nitrogen discharges have risen with an increase in sewage
flow stemming from population growth (Figure 6a). Phase III of the Baywide
Nutrient Reduction Strategy has scheduled an increased emphasis on nitrogen
removal from point sources.
Point Source Nitrogen Reduction Progress
100
Reported
90-
S 80-
2
.2
= 70-
Nutrient Reduction
Strategy Target
e
I 60-
8
as
z 50-
1995
1985
1990
2000
^ Phaael Phase II Phaae III
Figure 6a. Point Source Nitrogen Reduction Progress (Source: see references 7, 8)
Phosphorus discharges have been reduced at a faster pace than predicted in the
Baywide Nutrient Reduction Strategy. Annual discharges have dropped about 3
million pounds, a reduction of 40% of the 1985 load (Figure 6b). This is the year
2000 goal set in the 1988 Baywide Nutrient Reduction Strategy.
Point Source Phosphorus Reduction Progress
Reported
Nutrient Reduction
Strategy Target
6-
2000
1995
1990
1985
PhaMl PhaM II Phase III
Figure 6b. Point Source Phosphorus Reduction Progress (Source: see references 7, 8)
13
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Progress Report of the Baywide Nutrient Reduction Reevaluation
The upgrading of wastewater treatment plants has strengthened controls on
phosphorus. It has also begun to have a similar effect on nitrogen. A technology
known as biological nutrient removal (BNR) has been extensively studied in the
basin and is now in use among the treatment technologies for reducing point
sources of both nitrogen and phosphorus.12
Furthermore, compliance has improved with permitted discharge limits as shown
in Figure 7. The EPA and the states track the rate of non-compliance and have
found that since 1989 (when the Chesapeake Executive Council made compliance
a priority) the rate of non-compliance has been steadily declining.13
Significant Non-Compliance
20-
15-
5-
Major Chesapeake Bay
Discharge Permit Holders
t—i—r
1989
t—i—r
1990
T 1—I—I—I—|—I—I 1—|"
1986 1987 1988 1989 1990 1991
Figure 7. Significant Non-Compliance (Source: Chesapeake Bay Quarterly Noncompliance Report, Fourth Quarter 1991)
Nonpoint Source Nutrient Reductions
The Chesapeake Bay nonpoint source control program is responsible for reducing
the 218 million pounds of nitrogen (Table la, A13) and 15 million pounds of
phosphorus (Table lb, A13) that enter the Bay annually from nonpoint sources
in its watershed. Programs to accomplish this task were begun in the first phase
of the Baywide Nutrient Reduction Strategy's implementation and will play an
increasingly large role in the future. These jurisdiction-specific programs have
focused on research, technical assistance, education, and financial assistance for
implementation. They also are widely thought to have inspired voluntary source
reductions that cannot be measured. These programs have been further improved
through intensive management reviews.
The Chesapeake Bay Program's nonpoint source control portion of the Baywide
Nutrient Reduction Strategy emphasized controls on agriculture (including crop-
land fertilization and waste from livestock), paved surfaces, and construction in
urban areas. Whereas the Baywide Nutrient Reduction Strategy began as a
modification to traditional measures for controlling soil erosion, it has grown to
a level where it now incorporates many other control measures. The most
important additional control measure is the practice of nutrient management1415
in which animal wastes and fertilizers are applied to farmland in amounts carefully
calculated to meet the needs of the crops. This practice replaces the use of outdated
guidelines which promoted overuse and, consequently, runoff or leaching of
nutrients.
CSC.Lfl1B.12/91
14
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Chapter 2: Progress to Date
Controllable Nonpoint Source Estimates
110
100
90
| 80
1. 70
60
SO
40
Progress
J
Nutrient Reduction
J_ ,—
»iiii
1 I
Strategy Target
i
_____ , i— i '
1985
k-
Phase I
*l«-
1990
1995
Phase II
-H-4-
Phase III
2000
-*l
Figure 8a. Nonpoint Source Nitrogen Reduction Progress. Note:
Lower level reflects a revised estimate of 1985 nitrogen loads.
(Source: see reference 5, Watershed Model)
Nutrient Reduction
Strategy Target
Phase I
Phase II
Phase III
Figure 8b. Nonpoint Source Phosphorus Reduction Progress.
Note: Higher level reflects a revised estimate of 1985 phosphorus
loads. (Source: see reference 5, Watershed Model)
Documenting nutrient loadings from
nonpoint sources and progress made in re-
ducing those loads is much more difficult
than for point sources. Since it is not pos-
sible to monitor every nonpoint source,
appropriate methods must be developed to
estimate nonpoint source loads and the re-
ductions achieved by the state's control
programs. Recognizing that the initial esti-
mation methods used for the Baywide
Nutrient Reduction Strategy needed to be
more accurate, the Nonpoint Source Sub-
committee has been actively working on
improving the load estimation methods since
the Baywide Nutrient Reduction Strategy
was developed in 1988. The Chesapeake
Bay Watershed Model has been developed
and is being applied in the reevaluation to
provide a means to refine estimates of
nonpoint source nutrient loads and the re-
ductions due to different types of control
programs.
The first step in the reevaluation of the
Baywide Nutrient Reduction Strategy was
to check the 198S base year loading esti-
mates published in 1988. The Watershed
Model estimates for the reevaluation com-
pare favorably with the 1988 estimates.
Controllable nonpoint source nitrogen was
overestimated by approximately 9% and con-
trollable nonpoint source phosphorus was
underestimated by approximately 6% in the
Baywide Nutrient Reduction Strategy.
By incorporating this type of program track-
ing information into the Bay Watershed Model, nutrient loading reductions can be
estimated. Figure 8 depicts this progress toward achieving the states' nonpoint
source nutrient reduction goals. Implementation of nonpoint source control pro-
grams has resulted in a 12% and 8% reduction in controllable nonpoint source
nitrogen and phosphorus respectively. These rates of progress compare favorably
to the progress that was projected at the end of Phase II (1991) for the Baywide
Nutrient Reduction Strategy (12% reduction in nitrogen and 11% reduction in
phosphorus).
Figures 8a and 8b illustrate the revised base load estimates and the nonpoint source
nutrient reduction progress through 1990. As the figures indicate, although progress
on nonpoint source loading reductions are reasonably close to the Baywide Nutrient
Reduction Strategy projections, rates of load reductions will need to be accelerated
in Phase III of the Baywide Nutrient Reduction Strategy's implementation.
15
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Progress Report of the Baywide Nutrient Reduction Reevaluation
Portions of these decreases are reduction in nitrogen loads to ground water.
Because nitrogen in ground water is released very slowly, the benefits to Bay
water quality may not be seen for many years.
The programs implementing the Baywide Nutrient Reduction Strategy have not
invested heavily in the control of nutrients from forests, since forests represent
the least polluting land use in the watershed. They also planned no action in
reducing the amounts of nutrient pollution from atmospheric sources to the Bay
and its watershed, even though they were known to be a significant source of
nitrogen. But investigations during the first two phases of the strategy's imple-
mentation as well as the passage of the Clean Air Act Amendments in 199016 have
revealed that it may indeed be possible to reduce atmospheric sources of pol-
lutants. Such a reduction would reduce the nitrogen delivered by both rainfall
and dust to water and land thereby reducing the demands on other control
programs.
This progress does not include nutrient reductions in states that are not parties
to the Chesapeake Bay Agreement—Delaware, New York, and West Virginia.
Further information will be needed to characterize any load reductions that may
have been made in these states.
The largest nonpoint source of nitrogen and phosphorus loads continues to be
farmland. It has been the focus of nutrient reduction strategies in the past and
will need to continue to be targeted in the future.
Water Quality Trends and Characterization
The previous section discussed the progress made in reducing the point and
nonpoint sources that were the focus of attention in the first two phases of the
Baywide Nutrient Reduction Strategy. An analytical effort has been conducted
along with the assessment of load reductions to measure the impact that reduced
nutrient loads had on water quality. Findings from trend analyses of 1984-1991
Bay water quality monitoring data confirm the significant progress made in
reducing phosphorus from nonpoint source and municipal point source loads, as
well as the need for further progress towards reducing nitrogen loadings. These
trends are as follows:
Nitrogen Trends
• A 2% increase in total nitrogen was observed in the mainstem Bay.
(Figure 9a.)17
• Nitrogen concentrations increased significantly in the upper mainstem
(from the Susquehanna Flats to the mouth of the Patuxent River).
• Nitrogen concentrations increased significantly in the upper reaches of
several tributaries (Potomac, Rappahannock, York, Gunpowder, North-
east, Sassafras, Chester and Choptank).
• Nitrogen concentrations increased significantly in the lower section of
the James River.
CSC.LR1B. 12/91
16
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Chapter 2: Progress to Date
Total Nitrogen in Chesapeake Bay
Oct 84 Oct 85 Oct 86 Oct 87 Oct 88 Oct 89 Oct 90
Figure 9a. Total Nitrogen in Chesapeake Bay (Source : See reference 17)
Phosphorus Trends
A 19% decrease in total phosphorus was observed during a six-year period
in the mainstem Bay. (Figure 9b).17
Significant downward trends in phosphorus concentrations were ob-
served in the upper middle mainstem (between the Bay Bridge and the
mouth of the Patuxent River) and the lower mainstem (Mobjack Bay south
to the mouth of Bay).
Phosphorus concentrations declined in several tributaries as a result of
reductions in point source loadings (Patuxent and James, and less recently
in the Potomac).
Total Phosphorus in Chesapeake Bay
0.06
I 1 1 1 r
Oct 84 Oct 85 Oct 86 Oct 87 Oct 88 Oct 89 Oct 90
Figure 9b. Total Phosphorus in Chesapeake Bay (Source: See reference 18)
17
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Progress Report of the Baywide Nutrient Reduction Reevaluation
Dissolved Oxygen Trends
Oxygen in the Bay's waters, like oxygen in the air, is critical for the survival
of its living resources. Aquatic life in the Bay must breathe dissolved oxygen
to live. Thus, the levels of dissolved oxygen found in the Chesapeake are
an important indicator of the Bay's water quality.
The amount of oxygen that water can hold in solution is affected by both
temperature and salinity. The colder and less saline the water, the more
oxygen it can hold. To compensate for variations in water temperature and
salinity, the analysis was performed on the dissolved oxygen deficit—the
difference between the amount of oxygen that could be present theoretically
and the amount of oxygen that is actually present. The dissolved oxygen
deficit is the measure by which dissolved oxygen conditions can be improved.
Dissolved oxygen data were analyzed for long and short-term trends.1" The
analysis attempted to detect trends over a forty-year period, 1950 through
1990, during which time large natural variations in environmental conditions
occurred that affected dissolved oxygen. (Gaps in the data prior to 1984 may
also affect the results of the analysis).
• The volume of anoxic/hypoxic water in the mainstem has fluctuated
widely over the last four decades, often reflecting patterns of freshwater
inflow.
• The volume of anoxic waters has increased since 1950, based on available
data.
• No distinct trends have occurred in the dissolved oxygen deficit since 1984.
In summary, the six and a half years of baywide nitrogen, phosphorus
and dissolved oxygen data described here represent a minimum time
period over which to test whether significant trends exist in an estuary.
More subtle trends may be occurring that will require several more years
of monitoring to become detectable. The trends summarized here are
analyzed in the Water Quality Characterization Report.20
Water Quality Characterization
Through a detailed, baywide characterization of water quality conditions, new
insights into water quality patterns have emerged:
. Numerous areas in the Bay's tributaries, as well as previously identified
areas in the mainstem Bay, are impacted by low dissolved oxygen. These
tributaries include the Patapsco, Magothy, Severn, South, West, Rhode,
Patuxent, Potomac, Anacostia, Rappahannock, York, Chester, and Little
Choptank rivers, as well as Eastern Bay.
• Water column transparency in many tributary areas indicate habitat
conditions unsuitable for survival and growth of submerged aquatic
vegetation.
C8C.LR1B.12/91
18
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Chapter 2: Progress to Date
• Although some regions of the tributaries and mainstem and some time
periods have shown indications of both phosphorus and nitrogen limi-
tation of algal growth, a greater potential for phosphorus limitation has
appeared in the majority of regions and time periods.
As the Chesapeake Bay Program plans to address basin-specific nutrient loading
reduction targets, these specific water quality characterizations can guide nutrient
reduction programs to areas of greatest need.
Living Resources Characterization
Characterizations of the current status of twenty seven indicator species and two
biological communities in the Bay basins indicate that a number of key living
resources in Chesapeake Bay are below historical or potential resource levels.21
These basin-specific characterizations of living resources will be useful in
targeting nutrient reductions within specific tributaries as jurisdictions prepare
more detailed nutrient reduction plans.
19
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Chapter 3: The Reevaluation
THE REEVALUATION
In 1989, the Implementation Committee formed the Nutrient Reevaluation Workgroup
to assemble the results of modeling, research, monitoring and other information
and then integrate them with social and economic factors. The workgroup joined
forces with a number of respected consultants, public agencies and other Bay
Program participants to complete the Nutrient Reevaluation.
The workgroup also directed the compilation of eight reports that quantified point
and nonpoint source loads, characterized water quality and living resource
populations, and investigated the effectiveness and costs of various nutrient
control technologies. These reports synthesized the results of monitoring,
research and modeling efforts and described the baseline 1985 loads from which
the reductions were calculated. A project management timeline was developed
to keep this process on track (Figure 10).
The Nutrient Reevaluation: Project Management Timeline
1991
1992 and beyond
Interpret Progress
and Characterize
Current Conditions
Complete Background
Management
Studies
Assess Alternative
Management
Options
Update
Nutrient Reduction
Nutrient Load
Inventories5
Point Source
Reductions7
Nonpoint Source
Reductions8
Water Quality
Characterizations20
Water Quality Trends17'
19. 19 20
Living Resources
Characterization2'
Refined Water Quality
Objectives for
Living Resources
Habitats16-1f> 19
Model Refinements
• Watershed Model
• Water Quality Model
Assessment of
Technology
Effectiveness8
Assessments of Cost
Effectiveness8
• Baywide Water Quality
Projections
• Baywide Living
Resources Habitat
Quality Projections
• Pollution Control
Guidelines
- Effectiveness
¦ Implemenlability
• Cost
- Equity
• Assess Additional
Controls That May Be
Needed
• Conduct Public
Information and Reviews
• Outline Further
Technical Studies
Jurisdictional Tributary
Water Quality
Improvements
Tributary Living
Resources Habitat
Quality Improvements
Plan Additional Controls
as Needed
- Conduct Public
Information and
Reviews
- Program Further
Technical Studies
Figure 10. Source: Reevaluation Workgroup
21
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Progress Report of the Baywide Nutrient Reduction Reevaluation
Major Objectives of the Reevaluation
Based on the 1987 Agreement and the Baywide Nutrient Reduction Strategy, the
workgroup formulated the following major objectives of the reevaluation process:
1. Reevaluate the appropriateness of the 40% nutrient reduction commitment
based on available monitoring, modeling and research information.
The 40% nutrient (nitrogen and phosphorus) reduction goal was established
on the assumption that it would eliminate anoxia and prevent reintroduction
of nutrients from the sediments to the water. The 3-D Model is being used
to determine the adequacy of this reduction goal.
2. Refine nutrient reduction commitments as appropriate, based upon a
careful evaluation of the cost effectiveness, implementability, and living
resources benefits.
The Nutrient Reevaluation has investigated the cost effectiveness and imple-
mentability of various point and nonpoint source controls to meet the 40%
(or an adjusted) nutrient reduction goal and related living resource benefits.
The states will use this information along with experiences gained in imple-
menting Phases I and II of the Baywide Nutrient Reduction Strategy to refine
their strategies in the tributaries.
3. Provide a refined overall baywide nutrient reduction commitment including
basin-specific nutrient reduction targets.
The 1987 Agreement calls for an equitable achievement of the 40% nutrient
reduction goal by the year 2000 (the original goal called for across-the-board
reductions without any targeting). The 3-D Model will be used to determine
equitable targeted loadings, identifying the maximum allowable nitrogen and
phosphorus loads from each tributary to meet the 40% or adjusted reduction
goal.
4. Based on the work and analysis completed, provide guidance to the sig-
natories with regard to living resources, water quality and nutrient load
characterization to aid in revising the basin strategies most effectively.
Once equitable targeted loadings have been agreed upon, the states will
use available data, as appropriate, to determine the best mix of point and nonpoint
source controls to meet the identified tributary loadings.
The Baywide Nutrient Reduction Strategy developed by the Nutrient Reevalu-
ation Workgroup has focused on the following process:
1. setting appropriate water quality and living resource objectives;
2. establishing levels of key physical and chemical water quality parameters
necessary to support those objectives;
CSC.LR1B.12/91
22
-------
Chapter 3: The Reevaluation
3. evaluating the effectiveness and feasibility of pollution control options to
achieve the desired water quality;
4. estimating the cost of the various options; and,
5. recommending changes to the Baywide Nutrient Reduction Strategy that can
best reach the program's reconsidered objectives.
This approach is being used to review and restate water quality and living resource
objectives. The approach is also being used to examine the effectiveness and
implementability of the Baywide Nutrient Reduction Strategy in an engineering
context, cost efficiency in the economic context, and equitability in the social
and political context. To date, the first four steps of the process are well underway.
Water Quality and Living Resource Objectives
The Bay Program's highest priority is to restore the Bay's living resources.
Among the ways this will be accomplished is through water quality improvements
to be achieved through nutrient reductions. These reductions will increase
dissolved oxygen and improve water clarity. Submerged aquatic vegetation
(SAV) provides critical habitat for many of the Bay's organisms, but requires
relatively clear water to grow and photosynthesize.
While the importance of water quality and dissolved oxygen to the Bay's living
resources has been known for some time, more precise measures were necessary
to set objective goals. The Bay Program's application of the findings from
research and monitoring have produced a more refined picture of the water quality
needs of living resources. Efforts to develop quantitative restoration goals are
underway through the Living Resources Subcommittee, with an initial focus on
key fish species and SAV.
An initial task of the reevaluation was to characterize the living resource status
in the mainstem Bay and each major tributary. In the Baywide Nutrient Reduction
Strategy, only the Bay's mainstem living resources were considered. In current
work, the status of twenty-seven indicator species and two biological commu-
nities were compared with historical or potential resource levels.21
The Living Resources Subcommittee has prepared and is proposing quantifiable
physical and chemical parameters to be used as planning goals. They include;
1. the formation of dissolved oxygen habitat requirements which will protect
living resource habitats throughout the Chesapeake Bay.22 In the original
Baywide Nutrient Reduction Strategy, only a general goal of eliminating
anoxia in the deep portions of the Bay's mainstem was considered. Recently,
considerable work has been done to synthesize living resources habitat
requirements and to incorporate them in target concentrations of dissolved
oxygen which are both physically reasonable and biologically justifiable.
However, it should be recognized that these levels of dissolved oxygen might
not be attainable at all places and all times under any scenario of water quality
23
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Progress Report of the Baywide Nutrient Reduction Reevaluation
improvement. In some deep areas of the Bay, where mixing with surface
waters does not occur for long periods of time in summer, dissolved oxygen
may reach 1.0 mg/1 or below for extended periods even under pristine
conditions. Levels of dissolved oxygen in the proposed restoration goal will
provide sufficient oxygen to support the survival, growth, and reproduction
offish and invertebrates in the Chesapeake Bay by maximizing, to the greatest
spatial and temporal extent possible, the following dissolved oxygen con-
centrations:
• dissolved oxygen concentrations of at least 1 mg/1 at all times throughout
the Chesapeake Bay;
• dissolved oxygen concentrations below 3 mg/1 should not occur for longer
than 12 hours with the interval between excursions of this oxygen-
depleted water being at least 48 hours throughout the Chesapeake Bay
including subpycnocline waters;
• dissolved oxygen monthly mean concentrations of at least 5 mg/1 at all times
throughout the Chesapeake Bay with the exception of subpycnocline waters;
• dissolved oxygen concentrations at or above 5 mg/1 at all times and in
all locations of the Chesapeake Bay's spawning rivers with the exception
of subpycnocline waters.
• maintaining the existing minimum concentration of dissolved oxygen in
areas of the mainstem Bay and tributaries where dissolved concentrations
are above those stated in items above.
I. water quality-based habitat requirements for submerged aquatic vegetation
habitat restoration.23 This important resource was not explicitly considered
in the Baywide Nutrient Reduction Strategy. Preliminary quantitative grow-
ing season requirements have been established for four salinity zones for light
attenuation, suspended solids, chlorophyll, dissolved nitrogen and dissolved
phosphorus. (See the Technical Appendix for details).
These two categories of habitat requirements can be compared to existing
conditions and, in instances where projections are possible, be compared to
future conditions using computer models discussed in the next section.
Shallow areas of the Bay and tidal tributaries, which contain the most critical
habitat, are the areas in which the computer models are the least helpful in
predicting future water quality and habitat conditions.
Areas that will benefit most from improved water quality measured by the
dissolved oxygen and submerged aquatic vegetation requirements noted here
are shown in the technical appendix. Modeling discussions which follow
give needed perspective to future investments in water quality, however
because they forecast benefits to the mainstem of the Bay and not to the major
tributaries to the Bay, they underestimate the benefits nutrient reduction
programs are likely to have on habitat restoration.
State nutrient reduction strategies should attempt, in the future, to better
describe the benefits to tributary habitats.
CSC.LniB.l2/t1
24
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Chapter 3: The Reevaluation
Modeling Efforts
The Role of Models in the Baywide Nutrient Reduction Strategy
Mathematical models that compute pollution generation and its chemical and
biological effects on the Bay's water quality are being used to assess the
effectiveness and feasibility of pollution reduction alternatives. To perform this
analysis, the Reevaluation Workgroup used refined versions of the models that
guided the preparation of the 1988 Baywide Nutrient Reduction Strategy.
The models used are simply mathematical representations of pollution transpor-
tation and biological and chemical reactions seen in the real world. Models are
constructed for two basic reasons:
1. to provide tools for predicting the effects of pollution abatement controls on
future water quality; and,
2. to improve the understanding of the key physical, chemical and biological
processes that determine water quality.
Mathematical models do not make water quality
management decisions. They serve as aids in the
systematic analysis of such complex bodies of
water as the Chesapeake Bay, thereby contribut-
ing credible technical justification to the decision
process.
Previous Chesapeake Bay Modeling
Efforts
In 1987, two computer models of the Bay were
completed by the Chesapeake Bay Program. The
first was the Chesapeake Bay Watershed model
which predicted the delivery of nutrients to the
estuary from point and nonpoint sources above the
fall line and from nonpoint sources below the fall
line. The second was the Chesapeake Bay Steady-
State Model which simulated Bay water quality.
The results of these models showed that a 40%
reduction of nitrogen and phosphorus point source
and controllable nonpoint source loadings would
eliminate anoxia and maintain average dissolved
oxygen concentrations above 2.0 mg/1 in the
mainstem of the Bay and substantially reduce
algae in the Bay measured as chlorophyll a. This
result was the basis of the 40% nitrogen and
phosphorus reduction goal contained in the 1987
Chesapeake Bay Agreement. The simplistic out-
put of this model is contrasted to 1985 conditions
in Figure 11.
BOTTOM WATER DISSOLVED OXYGEN
UJ
fi
o
0
1
5
8 -
; -
6 -
NX
5 -
\\
« -
\\
40% NUTRIENT REDUCTION
3 -
2 -
j —
~ v^KISTING CONDITIONS
0 -
p
3
I 1
& g
I 1
t
s
SURFACE WATER CHIOBOPHYLL-A
EXISTING CONDITIONS
40% NUTRIENT REDUCTION
Figure 11. Simulated Water Quality from the Steady
State Model (Source: see reference 6)
25
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Progress Report of the Baywide Nutrient Reduction Reevaluation
The signatories to the 1987 Chesapeake Bay Agreement recognized that the early
Watershed and Steady-State Models had their limitations. The Watershed Model
was unable to adequately consider important best management practices (BMPs)
which control nonpoint source pollution and could not simulate instream sedi-
ment-nutrient interactions. The Steady-State Model could not simulate the
impacts of wet and dry year sequences—an important factor in the delivery of
nutrients to the Bay. Also in the Steady-State Model, the Bay was divided into
coarse lateral segments which limited its utility in understanding and evaluating
strategies to improve nearshore habitats. Although this model accounted for
sediment nutrient fluxes and oxygen demand on water quality conditions, the
fluxes could only be modified by external manipulation, an awkward and im-
precise process. Without a model-generated sediment response, it was not possible
to evaluate how long it would take the Bay to respond to reduced nutrient loadings.
Realizing the limitations of these models, the signatories called for this Nutrient
Reevaluation, using refined versions of the two models, planned when the original
goal was established.
Refinements to the Chesapeake Bay Models
The Watershed Model refinements include an improved and updated 1985
inventory of land uses and pollution sources, as well as the region's weather
patterns to compute the tributary river flows and nutrient loads delivered to the
Bay from the entire watershed, which includes New York, West Virginia, Penn-
sylvania, Virginia, the District of Columbia, Delaware, and Maryland. Other
refinements to this model include more advanced capabilities for simulating
agricultural fertilizer use and reductions due to nutrient management, and algo-
rithms for instream sediment transport that more accurately simulate nutrients
which are transported with sediment in rivers.
A 3-Dimensional Time-Variable Model was created to replace the Steady-State
Model used in 1988. This model, known as the "3-D Model," links two features—
the hydrodynamic component and the water quality component. The hydrody namic
component predicts the velocities, salinities, and temperature of waters in the
tidal portion of the Bay, including its tributaries. The water quality component
predicts the important aspects of water quality in the tidal Bay. These water
quality predictions include such things as the concentrations of nitrogen, phos-
phorus, and dissolved oxygen. This model is time-varying in that it simulates
water quality from a succession of naturally changing tributary river flows,
allowing a ten-year pattern to be analyzed instead of a single two-month summer-
averaged condition. Another important feature of the water quality component
is its ability to link nutrients in the water column to those in the sediment on
the Bay's bottom. This is accomplished through a sediment sub-model that
predicts nitrogen and phosphorus fluxes and sediment oxygen demand based on
the organic material that settles from the water column to the sediment layer.
CSC.LAlB.12/91
26
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Chapter 3: The Reevaluation
The Watershed Model and the hydrodynamic portion of the 3-D Model are
combined to produce input for the water quality portion of the 3-D Model
(Figure 12).
Chesapeake Bay Models
Meteorological
Input
Point Source
Loads
'
Watershed
Model
Land Use, Soil and
Geophysical
Characteristics
Surface
Winds
Flow
Rates
Nutrient
Loads
Sediment
Submodel
Three Dimensional Water Quality Model
| 3-D I r~~l r WateTl
I a M-I-.M K I
|_Compon_entJ |___yJ |_Compo_n_BnJJ
Atmospheric and Point
Source Loads Directly to
Tidal Bay
T
Ocean
Tides &
Currents
Chemical
& Biological
Constituents
Figure 12. Model Structure (Source: Adapted from Modeling of the Chesapeake Bay, CRC Publication No. 131)
These models were developed to address the following management issues:
• What impact do nutrient loads from point and nonpoint sources delivered by
the Bay's major tributaries have on the Chesapeake's water quality?
• How do these impacts change with reductions or increases in these sources?
• How are these impacts distributed across the Bay's habitats?
• How much of the nutrient loads to the Bay is natural and how much is related
to man-made sources, and to what extent can loads be controlled?
• How long will it take the water quality in the Bay to improve once nutrient
controls are fully implemented?
27
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Progress Report of the Baywide Nutrient Reduction Reevaluation
Seven model runs have been completed that begin to answer these questions.
These runs are described in greater detail in the Technical Appendix. They include
a simulation of base case conditions that establish the starting point for measuring
the impacts of various nutrient levels on the Bay. From this base, a "no action"
run simulated a 20% increase in nutrient loads to test whether further degradation
would result from the absence of effective controls. Once this was confirmed,
various reductions, some extreme in their assumptions, were simulated to estab-
lish the bounds of water quality improvement that can be expected from simulations.
Figure 13 shows that the changes in the nutrient loads that were simulated ranged
from an increase of 20% in both nutrients to decreases of up to 90%. The detailed
assumptions about these model runs are contained in the Technical Appendix.
These models have been used to date to project overall changes in dissolved
oxygen levels in the Bay. These projections give a more complete picture of the
changes in dissolved oxygen than was possible in 1988 using the Steady-State
Model.
Summary of Input Loads
Average Year
0)
a. -60-
Nitrogen
Q Phosphorus
Figure 13. Summary of Simulated Nutrient Loads. (Source: Dr. Robert V. Thomann, 1991)
CSCXfllB.12/91
28
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Chapter 3: The Reevaluation
Figure 14 shows change as "anoxic volume days," an index of the volume of Bay
waters with low dissolved oxygen simulated to occur during the June to October
season. In the future, model projections will also be related to the habitat
requirements presented in the first section of the Technical Appendix to this report.
The projections of future water quality confirm the utility of the models in
predicting the effects of pollution controls. The analysis of these projections has
also confirmed the 3-D model's use in its secondary function, that of understand-
ing the complex interactions that occur in the Bay itself. These simulations have
revealed the importance of the nutrients contained in ocean waters that flow in
and out of the Bay through tidal action. When nutrients are reduced in the Bay,
they are reduced in ocean waters that come from the Bay and which are conveyed
back into the Bay by the tidal action. Changes to the 3-D model are underway
to better simulate the fact that adjacent ocean water will be affected by changes
in the Bay's water quality.
Percent Change from Base
of Anoxic Volume Day
Wet Year
Q Dry Year
Average Year
-80
-120
c
o
*5
O
<
o
<0
m
m
vO
0s
O
O
IL
<
CM
%
GO
(M
%
C
o
o
3
"O
0)
a.
o
0>
Figure 14. Summary of Simulated Dissolved Oxygen Levels. (Source: Dr. Robert V. Thomann, 1991)
29
CSC.LR16.18/01
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Progress Report of the Baywide Nutrient Reduction Reevaluation
Although the 3-D Model is being continuously refined, several preliminary
observations can be made:
• The simulation of the Chesapeake Bay Program's goal of a 40% reduction
in controllable nitrogen and phosphorus will result in a reduction in total
nitrogen (18% reduction) and in total phosphorus (29% reduction) loads. The
relatively smaller nitrogen reduction is attributable to the impacts of atmo-
spheric deposition of nitrogen.
• Simulations named "Forest Reference" appear to simulate conditions beyond
those that can be achieved by any control programs.2425
• The simulation named "90% Reduction" probably approximates the condi-
tion of the Chesapeake Bay before it was burdened by the nutrient emissions
of modern society. From this simulation it is apparent that anoxia did not
exist in the Bay under undeveloped conditions in dry years.
Technology Effectiveness and the Costs of
Nutrient Load Reductions
The cause and effect relationships that can be quantified through the use of
models provide only a portion of the perspective needed to consider the
effectiveness of the Baywide Nutrient Reduction Strategy's management plans.
A review of the costs and efficiency of nutrient pollution control technologies
was undertaken to ensure that the feasibility of these controls is considered
part of the overall picture.26
Point Source Control Technologies
Point source nutrient removal technologies were reviewed.27'28 29'30 31 The reviews
included performance data from full scale, conventional wastewater treatment
plants operating in the Bay's watershed along with performance data from both
full scale and pilot advanced nutrient removal plants constructed and operated
under the 1988 Baywide Nutrient Reduction Strategy. Expected effluent levels
for phosphorus and nitrogen removal were developed for two averaging periods—
long-term (annual averages) and short-term (monthly averages) commonly used
in regulatory controls. From the results of these analyses, the costs and perfor-
mance of these technologies were agreed upon.
CSC.LRm.1M1
30
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Chapter 3: The Reevaluation
Nonpoint Source Control Technologies
Management investigations have been undertaken to determine the costs and
effectiveness of nonpoint source nutrient control measures, so that they can be
applied more effectively in the future.52"-34,35,36,37 These investigations:
• quantified the long, useful lives of appropriately installed and maintained
BMPs;
• helped develop consistent methodologies for estimating groundwater nutrient
contributions to the Bay;
• examined the effectiveness of voluntary nonpoint source implementation.38
Cost Effectiveness
Cost effectiveness is defined as the cost per pound of nutrients removed per year.
The nutrient removal effectiveness and relative costs of point and nonpoint source
technologies were extensively studied26 in the reevaluation process. A method
was developed for using this information in conjunction with the Chesapeake
Bay Watershed Model. This method will use relative cost comparisons of nutrient
reduction scenarios, helping to form cost effective strategies for point and
nonpoint source nutrient reductions.
31
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Chapter 4: Findings and Future Activities
FINDINGS & FUTURE ACTIVITIES
Findings
The information summarized in this report represents a major advance in our
understanding of the causes and results of nutrient enrichment in the Chesapeake
Bay and the actions needed to improve the Bay's condition. This effort could
not have been achieved without the coordinated efforts of managers, scientists
and citizens.
Additional work remains in finalizing the numerous technical reports that are the
foundation of the reevaluation and in using the complex mathematical models
of the Bay and its watershed to test various nutrient reduction alternatives.
Nevertheless, the work accomplished to date permits us to issue the following
preliminary findings:
Nutrient Loadings and Controls:
• Revised nutrient loading estimates for point sources of nutrients are close
to the 1987 estimates.
• Nutrient loading estimates for basinwide nonpoint sources were revised using
the Watershed Model. 1991 Watershed Model runs indicate that nonpoint
sources, including atmospheric deposition to the watershed, contribute ap-
proximately 77% of the nitrogen and 66% of the phosphorus on an average
basis.
• Bay wide, agricultural sources are dominant, followed by forest and urban
sources.
• The "controllable" fraction of nutrient loads from the Bay Agreement states
is approximately 47% for nitrogen and 70% for phosphorus. This controllable
fraction can be increased to 55% and 78% respectively, by considering loads
from states not party to the Bay Agreement. The percentage for nitrogen
would increase further if the large atmospheric deposition loads were con-
sidered to be controllable.
• We are ahead of schedule in meeting the 40% point source reduction target
for phosphorus and are starting to make progress in nitrogen removal.
• Preliminary results show the nonpoint source progress is reasonably close
to originally projected rates. Rates of nonpoint source nutrient load reduction
will need to be accelerated following the completion of the reevaluation at
the end of Phase II. Added emphasis on nonpoint source controls is vital
to the restoration of the Bay.
33
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Progress Report of the Baywide Nutrient Reduction Reevaluation
• A combination of several best management practices, referred to as a "Re-
source Management System" is the most effective means of reducing nutrient
loading from nonpoint sources. Results of the watershed model and cost
studies show that nutrient management is the single most effective measure
for inclusion in these resource management systems.
• Biological Nutrient Removal has been shown to be an effective alternative
to traditional point source technologies in some circumstances. However,
chemical addition technologies may still be required to meet point source
nutrient reduction objectives in some situations.
Status and Trends in the Bay's Condition:
• Trends in the Bay's nutrient concentrations since 1984 show significant
decreases in phosphorus levels in the mainstem and several tributaries and
slight increases in nitrogen in the upper mainstem and some tributaries.
• Water quality impacts related to nutrient enrichment, such as low dissolved
oxygen, are evident and have now been quantified in numerous tributaries
to the Bay as well as the mainstem.
• Living resource based water quality goals have been developed that will assist
in the interpretation of existing water quality impacts and projected improve-
ments under various management scenarios. Status and trends for key living
resources have been assembled for the Bay's major basins that confirm the
need for restoration actions.
Projections from Preliminary Model Results:
• Simulations of nutrient loading increases of 20% (projected growth with no
additional nutrient controls) result in approximately a 15 to 20% increase in
the extent and duration of Bay waters with dissolved oxygen levels less than
1 mg/1.
• Preliminary model runs show that a 40% reduction of the revised estimates
of controllable nutrient loads results in up to a 25% reduction in the extent
and duration of Bay waters with dissolved oxygen levels less than 1 mg/1.
• Nutrient reductions using maximum technological controls could reduce by
between 30% - 45% the extent and duration of Bay waters with dissolved
oxygen levels less than 1 mg/1.
• The shallow areas of the Bay and tidal tributaries which contain the most
critical habitats are the areas in which the computer models are the least
helpful in predicting future water quality and habitat conditions. Future
models should be refined to make these projections.
C8C.URie.12/91
34
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Chapter 4: Findings & Future Activities
Future Activities
Preliminary findings of the reevaluation are presented above. In the first half
of 1992, additional technical work will refine these findings and comments
received on this progress report will be incorporated. The final report, containing
recommendations, is scheduled to be presented to the Executive Council in
August, 1992. Following approval of the final report on the reevaluation, the
Bay Agreement jurisdictions will be responsible for developing implementation
plans to meet the revised nutrient reduction goals. These jurisdiction-specific
and basin-specific plans are scheduled to be drafted by December, 1993.
The nature of the refinements to the preliminary findings presented here will be to:
• confirm the 40% reduction goal or provide a revised basin-wide nutrient
reduction goal and specific nutrient load reduction targets for major basins
to most effectively achieve improvements in the Bay's condition;
• further examine the relative benefits of nitrogen and phosphorus controls;
• examine, through the use of models, the reduced atmospheric deposition
expected to result from air quality controls that will be necessary to comply
with the Clean Air Act. Additional modeling will be necessary to determine
the extent to which these controls will reduce sources of nutrients important
to the Chesapeake Bay.
• estimate the value of nutrient reduction alternatives using a broader suite of
water quality parameters that have relevance to living resource habitats;
• thoroughly consider the implementability and cost of the recommended
nutrient load reduction targets.
These factors will be evaluated with additional runs of the mathematical models
and more detailed analysis and synthesis of information compiled in the reports
prepared as part of the reevaluation.
The Baywide Nutrient Reduction Strategy and the state implementation plans it
contains will have to be reviewed and updated as necessary to reflect this
reevaluation.
Information compiled during the reevaluation will provide valuable guidance to
the jurisdictions in developing their plans. This information, as described in
previous section of this report, will include detailed nutrient loading estimates,
evaluations of water quality and living resources status and trends in the mainstem
and tributaries, and an accounting of available technologies and costs for point
and nonpoint source nutrient controls.
The process outlined above will extend the goals and principles of the 1987
Chesapeake Bay Agreement while ensuring that the nutrient reduction plans of
the signatories are realistic and will lead to significant progress in restoring the
Chesapeake Bay by the year 2000.
35
CSC.LAlB.t2/9t
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Technical Appendix
TECHNICAL APPENDIX
This appendix describes in detail the development and use to date of the proposed
living resource habitat requirements, the simulation of future Bay water quality
using the Watershed and 3-D models, and the detailed assessments of technologies
and costs that have been prepared as a part of the reevaluation process.
Water Quality and Living Resource Objectives
Reduced quantities of nutrients will lead to greater water clarity essential to the
return of submerged aquatic vegetation which forms important habitat and
elevates levels of dissolved oxygen required to support fish populations. While
the importance of water clarity to submerged aquatic vegetation has been gen-
erally known for some time, more precise relationships were needed to set goals.
Research undertaken by the Bay Program provided an understanding of the
relationships between nutrient concentrations, total suspended solids, water
quality, and the survival of submerged aquatic vegetation, as well as the health
and survival of other Bay living resources. This knowledge will allow planning
goals for nutrient concentrations to be formally adopted by the Program as the
foundation of the restoration plan for these resources.
Our understanding of living resource habitat needs has progressed; priorities can
now be assigned to programs that first address areas of critical local concern,
and can then be used to address larger regional concerns. Two sets of habitat'
requirements are used in this assessment—the first is for submerged aquatic
vegetation (SAV), and the second is for dissolved oxygen.
Submerged Aquatic Vegetation
The survival and growth of the Bay's SAV are significant concerns that need to
be addressed in restoration and protection plans for each of the Bay's major
tributaries. Extensive studies have shown that the presence of SAV corresponds
to a set of water quality parameters such as light attenuation, total suspended
solids, chlorophyll a, dissolved inorganic nitrogen and dissolved inorganic phosphorus
(Table Al).
These habitat requirements are based on zones of salinity and apply to areas
delineated as existing habitat or as areas for potential SAV regrowth.23 Figures
Al and A2 show areas in which the SAV habitat requirements—dissolved
inorganic nitrogen (DIN) and dissolved inorganic phosphorus (DIP)—are and are
not being met. These are the areas of greatest need for SAV habitat restoration.
The dissolved inorganic nitrogen habitat requirements were not achieved in about
half of the Bay, including the upper central mainstem (see Figure Al). Portions
of several tributaries including the Patapsco, Magothy, middle Patuxent, middle
York, lower James, Chester, Choptank, Nanticoke and Wicomico rivers also failed
to meet this parameter.
37
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Progress Report of the Baywide Nutrient Reduction Reevaluation
Chesapeake Bay SAV Habitat Requirements
SAV HABITAT SAV HABITAT
REQUIREMENTS FOR REQUIREMENTS FOR
ONE METER RESTORATION TWO METER RESTORATION
Salinity
Regime
Light
Attenuation
Coefficient
Total
Suspended
Solids
(mg/l)
Chlorophyll
a
(Hg/1)
Dissolved
Inorganic
Nitrogen
(mg/l)
Dissolved
Inorganic
Phosphorus
(mg/l)
Critical
Lire
Period(s)}
Light
Attenuation
Coefficient
(m1),
Critical
Life
Perlod(s)3
Tidal Fresh
<2
<15
<15
—
<0.02
April-
October
<0.8
April-
October
Oligohaline
<2
<15
<15
—
<0.02
April-
October
<0.8
April
October
Mesohaline
<1.5
<15
<15
<0.15
<0.01
April-
October
<0.8
April-
October
Polyhaline
<1.5
<15
<15
<0,15
<0.02
March-
November
<0.8
March-
November
1. The Chesapeake Bay SAV habitat requirements are applied as median values over the April-October critical life period of tidal fresh, oligohaline,
and meiohaline salinity regimes. For the polybaline salinity regime, the SAV habitat requirements are applied as median values from the combined
March-May and September-November data.
2. Tidal fresh = <0.5 ppt: oligohaline = 0.5-5 ppt. mesohaline = >5-18 ppt; and polyhaline = >18 ppt.
3. For determination of Secchi depth habitat requirements, apply the conversion factor Secchi depth = 1.45/light attenuation coefficient.
Table A1. Chesapeake Bay SAV Habitat Requirements, (Source: SAV Technical Synthesis, U.S. EPA Chesapeake Bay
Program Office, Annapolis, Maryland)
The dissolved inorganic phosphorus habitat requirements were met throughout
most of the mainstem bay. This achievement is shown in Figure A2. Portions
of a number of major tributaries including the Patapsco, Patuxent, upper Potomac,
upper York, James, Choptank, Nanticoke and Wicomico rivers failed this measure
of habitat quality.
In recognition of the critical role SAV plays in the Chesapeake Bay ecosystem,
vater quality restoration priorities are being considered which will set priorities
to first protect existing SAV resources, then expand existing SAV distribution,
and finally restore SAV to areas currently unvegetated but containing potential
SAV habitat. Analyses are underway to refine this analysis so that these priorities
can be further used in the tributary strategies of the states.
csc.Lftie.itt»i
38
-------
Technical Appendix
Existing Dissolved Inorganic Nitrogen Conditions
Achieved habitat requirements
m Failed habitat requirements
| | Habitat requirements not applicable
Figure A1. Simulated existing dissolved inorganic nitrogen conditions presented as achievement of the proposed
dissolved inorganic nitrogen submerged aquatic vegetation habitat requirements. (Source: Chesapeake Bay Water
Quality Monitoring Data Base)
39
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Progress Report of the Baywide Nutrient Reduction Reevaluation
Existing Dissolved Inorganic Phosphorus Conditions
Bill Achieved habital requirements
| Failed habitat requirements
Figure A2. Simulated existing dissolved inorganic phosphorus conditions presented as achievement of the proposed
dissolved inorganic phosphorus submerged aquatic vegetation requirements. (Source: Chesapeake Bay Water Quality
Monitoring Data Base)
CSC LR1B12/91
40
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Technical Appendix
Dissolved Oxygen
Dissolved oxygen habitat requirements constitute the second set of living re-
source requirements important to the reevaluation. Dissolved oxygen require-
ments were derived through analysis of dissolved oxygen tolerance information
collected for over forty three Chesapeake Bay species22 in order to identify areas
of greatest need for living resource habitat restoration. Dissolved oxygen habitat
requirements have been translated to apply to a seasonal time scale for direct
comparison with model-forecasted dissolved oxygen for alternative nutrient
reduction programs. These habitat requirements, together presented as a pro-
posed dissolved oxygen restoration goal, should assure species survival as well
as protect sensitive life stages.
Figure A3 shows the achievement or non-achievement of the dissolved oxygen
goal throughout the Chesapeake Bay is exceeded most frequently in the mainstem
and in the lower tributaries between the Bay Bridge and the Rappahannock River.
Areas north of the mouth of the Patuxent to north of Baltimore suffer depressed
oxygen levels over 50% of the time. Areas further north of this zone experienced
depressed oxygen as well, although less frequently.
Based on this comparison of living resource habitat needs and existing conditions,
dissolved oxygen improvements should be targeted towards the areas identified
in figure A4 beginning in the lower tributaries, moving out to the surface waters
of the mainstem and eventually down into the deep trough.
41
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Progress Report of the Baywide Nutrient Reduction Reevaluation
Existing Dissolved Oxygen Conditions
Achieved habitat requirements
Failed habitat requirements
Mainstem Bay • Depth Perspective
Figure A3. Simulated existing dissolved oxygen conditions presented as attainment of the proposed dissolved oxygen
restoration goal 90% of the time. (Source: Chesapeake Bay Water Quality Monitoring Data Base )
CSC LR1B. 12/91
42
-------
Technical Appendix
Living Resource Habitat Dissolved Oxygen Restoration Priority Regions
Lower Potomac
River
Upper Central Malnstem Bay
Lower Chester River
Eaatern Bay
Lower
Patuxent
River
Lower Rappahannock
River
York River
Middle Central Malnstem Bay
Lower Central Malnstem Bay
James River
Figure A4. Priority regions for dissolved oxygen restoration identification based on percent achievement of
the goal matched with key living resource habitats. (Source: Chesapeake Bay Program Office).
43
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Progress Report of the Baywide Nutrient Reduction Reevaluation
The Bay Program now has:
• The tools necessary to establish basin-specific water quality restoration
priorities based on the needs of the Bay's living resources and a more in-
depth understanding of the water quality standards for critical SAV habitats.
When this information is translated into planning targets, it will be a useful
tool in refining the Baywide Nutrient Reduction Strategy.
• The perspective to gauge the significance of dissolved oxygen levels pro-
jected by the Chesapeake Bay Water Quality Model as the Bay Program
considers control programs to guide subsequent state tributary plans.
Model Refinements
The refinement of the Steady-State Eutrophication Model into a more detailed
time-variable model of water quality in the Chesapeake Bay was the milestone
foreseen in the 1987 Chesapeake Bay Agreement when it called for a reevaluation
of the nutrient reduction goal.
The 3-D Model linkage to the Watershed Model was undertaken to coincide with
this refinement. Valuable insights can also be obtained from analyzing predictions
of the Watershed Model independent of the 3-D Model.
The set of linked Chesapeake Bay models has been subjected to rigorous review
by the Modeling Evaluation Workgroup. This group has concluded that the models
are valid and can be used for planning purposes related to the cleanup of the
Chesapeake Bay. The Modeling Subcommittee of the Chesapeake Bay Program
has also endorsed the use of these models.
As a result of the extensive development work, these linked models can now be
used to investigate variations in the main Bay water quality under nutrient
loadings different from those used in the calibration. A group of loading
simulations have been made. The purposes of these initial simulations were to:
1. confirm the models' credibility over a range of loadings to ensure its sat-
isfactory performance;
2. provide a preliminary assessment of the adequacy of the Baywide Nutrient
Reduction Strategy; and,
3. investigate whether alternative nutrient management programs might be more
effective in restoring Bay water quality.
Updating the Watershed Model
The current Chesapeake Bay Watershed Model39 is a refinement to a watershed
model used to generate nutrient loadings for input to the Steady-State Bay
CSC.LniB.1M1
44
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Technical Appendix
Eutrophication Model. The Watershed Model requires inputs of meteorological
conditions, land-use patterns and other watershed characteristics to estimate
nutrient loadings and streamflow contributed to the tidal waters from the water-
shed.
From the segmentation scheme of the original model, ten major tributary basins
with sixty-three model segments were retained (Figure A5). The 1978 base year
for landuse data was revised and updated to reflect 1985. Improvements to the
portion of the model dealing with agricultural land uses were made to include
more advanced capabilities for simulating agricultural fertilizer use and reduc-
tions due to nutrient management. The model algorithms for instream sediment
transport were refined to more accurately simulate nutrients associated with
sediment transported in the rivers. Finally, the model calibration period was
extended through 1987 to take advantage of additional water quality data collected
on the major rivers.
Model Segments
Above Fall Line
Below Fall Line
Figure A5. Model Segments. (Source: Chesapeake Bay Program Office)
45
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Progress Report of the Baywide Nutrient Reduction Reevaluation
The precision of the Watershed Model calibration is seen in how well the predicted
nutrient loads correspond with loads derived from monitored water quality.
Figure A6 shows the comparison for loads from the Conowingo Dam on the
Susquehanna River. The dotted line shows loads taken from a regression equation
that relates flows and loads. The solid line shows the predictions of the Watershed
Model.
Despite these substantial improvements, the Watershed Model does not have
sufficient resolution to target control measures at the sub-basin level. Additional
refinements need to be undertaken on the major sub-basins to provide information
for watershed-specific management decisions.
700000
600000
500000
400000
300000
200000
100000
0
1984 1985 1986 1987 1988
50000 -
40000 -
30000 -
20000 "
10000"
o-
1984 1985 1986 1987 1988
Method: RIVINP CBLO
Box represents +/- 2 std error of prediction
Figure A6. Susquehanna at Conowingo. Total Nitrogen and Total Phosphorus Loads. (Source: Maryland Department
of the Environment)
Susquehanna at Conowingo
Total Nitrogen Load
Susquehanna at Conowingo
Total Phosphorus Load
i
n
i
I I I
CSC.LfllB.12/91
46
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Technical Appendix
Creating the 3-D Water Quality Model
The Chesapeake Bay Water Quality Model (3-D Model) predicts the water quality
response of the Bay to changes in nutrient loadings due to pollution control efforts.
The model is composed of two components:
The Hydrodynamic Component
Water quality in the Chesapeake Bay is very dependent on physical processes
such as flow and circulation patterns, mixing and dispersion, water temperature,
and salinity distribution. As an example, the degree of stratification due to the
vertical salinity distribution is a major factor contributing to low dissolved oxygen
in the bottom waters of the Bay. To properly represent these physical processes
in the water quality component, it was essential to develop a hydrodynamic
component. The development of a hydrodynamic component was initiated during
modeling efforts prior to 1988, but the time frame did not allow its successful
completion.
The hydrodynamic component of the tidal Chesapeake Bay is represented by 3948
computational cells, 734 horizontal cells, and between 2 to 15 vertical layers.
Grid resolution is approximately 10 km longitudinally, 3 km laterally, and 1.52
m vertically (Figure A7). The hydrodynamic component requires input of flow
rates at the fall line, wind distribution throughout the tidal Bay, and tidal heights
and salinities at the ocean boundary. The output from the component model is
currents, temperature, and salinity at each of these cells. The hydrodynamic
component was calibrated and validated using data from 1980, 1983 and 1984
through 1986.
The Water Quality Component
The water quality component uses the same segmentation scheme as the hydro-
dynamic component (see Figure A7), and requires information from both the
Watershed Model and the hydrodynamic component. The water quality com-
ponent solves mathematical equations that represent the physical, chemical, and
biological interactions among twenty two primary water quality parameters. This
model component was validated using monitoring data collected from 1984
through 1986.
Measures of nutrient fluxes to the water column from the sediment layer are
obtained through a sediment sub-model which interacts continuously with the
water quality component. Through settling, the sediment receives particulate
organic matter (carbon, nitrogen, phosphorus and silica) from the water column.
The particulate matter is converted to soluble end products through mineraliza-
tion. The difference between the concentrations of the nutrients in the sediment
and in the water column determines the magnitude and direction of the fluxes.
47
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Progress Report of the Baywide Nutrient Reduction Reevaluation
Chesapeake Bay Hydrodynamic and Water Quality Model Grid
Figure A7. Chesapeake Bay Hydrodynamic and Water Quality Model Grid. (Source: U.S. Army Corps of Engineers)
CSC.lfilB.12/91
48
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Technical Appendix
Simulating Future Water Quality
The simulations are constructed under a series of common assumptions that
provide a basis for comparing the relative response between different nutrient
loading patterns. These assumptions are summarized as follows:
1. The change in nutrient loading to the Bay is assumed to occur instantly and
to continue at the new level.
2. The model is run for ten years at the new loading rate with a consistent pattern
of changing hydrologic conditions. For each simulation, a ten year hydrologic
sequence representing the Bay hydrology from 1979 to 1988 was constructed
from hydrologies typical of wet, average, and dry years. A wet year was
represented by 1984 hydrology, an average year by 1986 hydrology, and a
dry year by 1985 hydrology. The river flows delivering nutrients to the Bay
during the decade ending in 1988 were simulated by assembling a sequence
of wet, average, and dry hydrologies to approximate what actually occurred.
The hydrology sequence for the scenarios is shown in Table A2.
Year
Condition
1979
Wet
1980
Dry
1981
Dry
1982
Average
1983
Average
1984
Wet
1985
Dry
1986
Average
1987
Average
1988
Dry
Table A2. Hydrology Sequence Used in the Ten Year Simulation. (Source: Modeling Subcommittee)
3. Ocean boundary nutrient concentrations were initially set at observed 1984-
1986 values, and they had a significant impact on the Bay's phosphorus levels.
Later runs reduced ocean boundary concentrations by amounts expected from
reduced phosphorus discharges in the Chesapeake Bay watershed. The final
version of the 3-D Model will have ocean boundary concentrations which
will be adjusted internally within the model run in response to load reduction
scenarios. Methods of computing this interaction continue to be refined.
49
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Progress Report of the Baywide Nutrient Reduction Reevaluation
4. Each scenario is evaluated based on the ninth year of the ten year simulation.
Though this year does not represent the hydrologic conditions used to
establish the baseline load reductions (determined by the Watershed Model),
it is the year within the 3-D Model simulation period that is most like the
long term average flow.
Description of Preliminary Scenarios and Nutrient
Loadings
To date, a total of seven sensitivity runs have been made using the preliminary
calibrated model of the Bay. The scenarios were chosen to provide initial results
for a range of loading conditions, not all of which are technologically achievable.
Several sensitivity runs were included to test the behavior of the model under
a wide range of load changes. Others were included to provide estimates of base
case, forest, and controllable loads. For all scenarios, the ten year hydrology
sequence previously discussed was applied. The first five years of the simulation
equilibrate the sediment to the sensitivity run loads. Analysis is focused on the
last five years of the sensitivity run. Special emphasis is given to the ninth year
in this report because it was near average conditions. Also, ocean boundary
conditions representative of 1984-1986 observed conditions were used for all
scenarios except numbers 3, 6 and 7 which test the lower ocean concentrations
expected to result from reduced Bay nutrient discharges. The scenarios are
described in Table A3.
Scenario
Number Name
Description
No action
120% of base case loads simulating the con-
tinuing growth of pollution sources.
2
Base case
1984-1986 loads serving as the program's
starting point.
3
40% -B Reduction 60% of the load difference between base case
and Forest Ref. #1
4
Forest Ref. #1 All forest in signatory states
5
Forest Ref. #2A All forest in all states, no atmospheric input
to the tidal Bay
6
Forest Ref. #2B Same as Forest Ref. #2A but reduced ocean
nutrients levels
7
90% Reduction Approximately 90% reduction of base case
loads, no atmospheric input to the tidal Bay
Tabla A3. Completed Scenario Runs. (Source: Modeling Subcommittee)
CSC-LR1B.12/91
50
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Technical Appendix
Figure A8 shows the relative nitrogen and phosphorus loads in each of these
simulations. The percent load reductions shown in this figure are different from
the reductions implied by some of the names assigned to the simulation because
the hydrology simulated in the ninth year was not identical to hydrology used
to define the conditions of the simulation.
The nitrogen and phosphorus loading changes for each of these seven simulations
are shown in the figure below. The loads shown are input loads that originate
from the air and land. These include loadings from tributaries at the fall line,
point and nonpoint sources originating below the fall line, and atmospheric
sources.
The model brings in other sources such as those that enter the water column from
the sediments and the loads that intrude into the Bay from the ocean. These loads
are important, and they vary as a function of reductions in loads from the land
and air. The sediment and ocean loads will be depicted in later reports.
20
0
8> "20
I
~ -40
i
& -60
-80
-100
Figure A8. Average Year of Simulation - Input Loads Only. (Source: Dr. Robert V. Thomann, 1991)
Summary of Input Loads
Average Year
Nitrogen
~ Phosphorus
c
O
<
o
(0
CO
CD
CD
£
O
IL
CD
S
£
C
0
1
1
tr
8
51
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Progress Report of the Baywide Nutrient Reduction Reevaluation
Some observations about these simulations include:
• The 40% reduction scenario (the current nutrient reduction goal) will result
in a relatively small decrease in nitrogen loading (18%). Phosphorus
reduction will be higher (29%). The reason for the small nitrogen decrease
is the relatively high nitrogen loading attributed to atmospheric deposition.
• The 90% load reduction simulation approximates natural background nitro-
gen loading for all basin states. 24
Other observations include:
• The relative contribution of the ocean boundary loads is significant and
becomes more important as upstream loads of phosphorus and nitrogen are
simulated to decrease.
• The nitrogen and phosphorus load from the non-signatory states can be
calculated from the information contained in Table la and lb (see Chapter
2). Without considering atmospheric deposition which originates both within
and outside of the watershed, non-signatory states contribute about 11 % of
the total nitrogen load and 8% of the total phosphorus load. This is 18%
of the controllable nitrogen and 11% of the controllable phosphorus dis-
charged in the states that are party to the Chesapeake Bay Agreement.
• Direct atmospheric deposition of nitrogen to Bay surface waters (34.6 million
lbs/year), is quite large. Successful implementation of the 40% nitrogen
reduction goal will remove 70.1 million lbs/year of nitrogen from land-based
sources. This reduction is only twice as large as the nutrient load deposited
from the atmosphere to tidal waters.
Summary of Simulated Water Quality Responses
There are several possible measures to evaluate the simulated responses of the
main Bay to the loading reductions. The emphasis in this review will be on the
dissolved oxygen (DO) response.
Measuring other indices of dissolved oxygen responses also provide useful ways
to interpret progress. The length of time that the Bay has DO less than 1 mg/
1, and the volume over which this condition is experienced can be expressed as
anoxic volume-days. This measure is expressed as a percent of change from the
base case.
C8C.LR1B.WV1
52
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Technical Appendix
Figure A9 shows the response for the second measure, the percent change in
anoxic volume-days projected through the simulations. In the "no action"
alternative, the volume-days below 1 mg/1 would increase by about 8% while
the 40% Reduction simulation reduces the anoxic volume-days by between 15
and 25%. Note that the 90% reduction scenario nearly eliminates the anoxic
volume-days, indicating that at no time or place was the DO calculated to be below
1 mg/1. This figure is presented with a range of hydrologic conditions, showing
the variations in control effectiveness that are experienced under different con-
ditions. In general, the percent reduction in anoxic volume for these simulations
is less than the percent reduction in nitrogen and phosphorus loading. This is
believed to be due to the influence of phosphorus release from sediment.
Average Year of Simulation • Percent Change from
Base of Anoxic Volume-days
Wet Year
Q Dry Year
Average Year
-120
c
o
•MB
o
<
o
o
a
m
m
*
<
m
¦
CM
CM
nP
o^
hm
o
%
%
O
h.
k.
LL
O
LL
O
U-
o
3
S
K
>P
0)
Figure A9. (Source: Dr. Robert V. Thomann, 1991)
53
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Progress Report of the Baywide Nutrient Reduction Reevaluation
The preliminary conclusions emerging from the analyses of these simulations are:
1. If nutrient loads were allowed to increase by 20% over current levels (the
"no action" case) the overall extent and duration of poor DO are expected
to deteriorate and water quality would be further degraded.
2. Under the 90% load reductions scenario (which approximates natural back-
ground nutrient loads typical of colonial times), anoxia probably did not exist
to any substantial degree.
3 A 40% reduction of controllable loads provides a modest 15 to 26% improve-
ment over current anoxic volume-days, but a substantial improvement over
the "no action" case.
4 For greater improvements in DO, additional load reductions will be necessary.
5. Such additional load reductions might include application of increased tech-
nological control on point and nonpoint nutrient sources, reductions in
atmospheric nitrogen deposition, and reductions of nutrient loads in non-
signatory states.
Technology Effectiveness and Cost for Nutrient
Load Reductions
Point Source Control Technology
A special assessment reviewed available point source nutrient removal technolo-
gies including performance data from full-scale, conventional wastewater treat-
ment plants operating in the region and from both full scale and pilot advanced
nutrient removal plants constructed and operated under the Baywide Nutrient
Reduction Strategy. Expected effluent levels for phosphorus and nitrogen re-
moval were developed for two averaging periods: long-term (annual averages)
and short-term (monthly averages) commonly used in regulatory controls12. The
results of these analyses have been agreement on the costs and performance of
these technologies.
Nonpoint Source Control Technology
Management investigations have been undertaken which lead us to better under-
stand the costs and effectiveness of nonpoint source nutrient control measures
so that we can better apply them in the future. They have:
• confirmed the long useful lives of BMPs;
developed consistent methodologies for groundwater nutrient contributions
to the Bay; and,
• examined the effectiveness of voluntary nonpoint source implementation.
CSC.LR1B.12/91
54
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Technical Appendix
Cost effectiveness is defined as the ratio of the cost per pound of nutrient removed
per year. The nutrient removal effectiveness and relative costs of point and
nonpoint source technologies were also extensively studied in the reevaluation
process. A method was developed for using this information in conjunction with
the Chesapeake Bay Watershed Model. The method will allow relative cost
comparisons of nutrient reduction scenarios to determine cost effective strategies
for point and nonpoint source nutrient reduction.
Process and Approach
Point Source Control Costs
The focus of the analysis was on the financial cost effectiveness of upgrading
municipal wastewater treatment plants for nutrient removal since this represented
the largest source of nutrients among the point sources. The bases for the cost
estimates were extensive studies undertaken as the original Baywide Nutrient
Reduction Strategy was being prepared.Z7 Z8,29,30,31
• For nitrogen removal retrofits, the selection of chemical addition (methanol)
or biological nitrogen removal without the use of chemicals will depend on
site-specific constraints. Therefore, despite the cost effectiveness of biologi-
cal nitrogen removal, it cannot be concluded that nitrogen removal without
the use of chemicals should be the technology of choice for retrofitting all
municipal treatment plants.
• Seasonal nitrogen removal may be more cost effective than annual removal.
Costs can significantly increase for annual removal because at lower tem-
peratures biological processes require longer wastewater retention times.
Longer retention times require larger reactor tank sizes thereby increasing
costs.
• Biological Phosphorus Removal (BPR) can be a cost effective alternative for
phosphorus removal (Figure A10). It has potential for cost savings in
chemical use and sludge handling. However, plants that implement BPR
technologies may require chemical phosphorus removal facilities to comply
with permits mandating effluent requirements below 1.0 mg/1.
Nonpoint Source Control Costs
The reevaluation focused on the financial cost effectiveness of agricultural and
urban Best Management Practices (BMPs).
Watershed Model runs were used to determine the aggregate nutrient reduction
for each control scenario. Nutrient reductions for each scenario were calculated
as the difference between the loads generated by a particular scenario and the
"base case" model run.
55
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Progress Report of the Baywide Nutrient Reduction Reevaluation
The cost effectiveness of individual nonpoint source control practices should not
be judged only on their individual performance, but rather as combinations of
BMPs aggregated into "Resource Management Systems" that together reduce
the pollutant loads.33 Different BMPs remove different proportions of nitrogen
and phosphorus, and some are more effective in some settings than others.
Controls, for instance, that work on the principle of retaining storm flows to reduce
soil erosion and phosphorus pollution may shunt nitrogen to the ground water
where it will eventually be transported into the Bay. For this reason, the aggregate
performance and cost of an entire system must be examined before its combined
merits can be fully assessed. The Watershed Model provides a mechanism for
doing this.
A cost effective Resource Management System, however, must be comprised of
efficient and low cost components. Preliminary cost effectiveness ratios for point
and nonpoint source nutrient reduction controls are summarized for use in
assembling these systems (see Figure A10). The relative costs and performance
of resource management systems make them powerful tools in guiding future
nutrient reduction programs.
Nutrient Control Costs for Nitrogen and Phosphorus Removal
100
I 90
g 80
| 70
| 60
| 50
'b
3 40
0 30
| 20
1 10
0
NITROGEN
1
Nutriant Contvn.
mngmnt UHaga
Cham,
addition
BNR
Animal
wnte
Urban
PHOSPHORUS
100-1
90"
80-
70-
60-
1
50-
"1
40-
c
¦5
30-
S
20-
1
10"
o-i
I
I
14B6
s
W7
BNR Nutrlml Cham. Contvn. Animal Urban
mngmnt addition tillaga waata
Lagand:
I"
I
not fchown
toicata
Figure A10. Comparative Nutrient Control Costs for Nitrogen and Phosphorus Removal Per Year.
(Source: see reference 26)
C8C.LRie.tW1
56
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Technical Appendix
• Results of the Watershed Model show nutrient management to be the most
cost effective control technology . Other technologies in combination with
in-field BMPs such as conservation tillage and winter cover crops are cost
effective management alternatives for nutrient reduction.
• Winter cover crops are very effective in removing excess nitrates during the
cold season.
• Conversion of highly erodible land to permanent vegetation is cost effective
since vegetation can considerably reduce sediment erosion, runoff, and
nutrient loads entering the water.
• Animal waste has been identified as a significant contributor of nutrient loads
to the Bay. Although the cost is high, animal waste management systems
should be considered important components of "Resource Management
Systems." More emphasis should be given to reducing these costs.
• Preliminary results show urban BMPs to be the least cost effective nutrient
control technology, however some urban BMPs have other important func-
tions which were not addressed in this report.37
The analysis of technology effectiveness and costs of nutrient removal provides
the basis upon which the most cost effective nutrient controls can be selected.
It cannot be used to predict the absolute cost of implementation of nutrient
removal programs. Those costs will depend on factors such as local/state/federal
government cost share programs, schedule of implementation, and other factors,
in addition to site-specific conditions which can significantly affect costs and
the application of nutrient removal technologies.26 The potential economic
benefits of nutrient reduction programs have been demonstrated. These benefits
were not evaluated but may need to be factored into an implementation plan.
57
CSC.LR1B.12/91
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GLOSSARY
Glossary
Algae: Any of a group of aquatic plants, including phytoplankton and seaweeds,
ranging from microscopic to several meters in size.
Anoxia: Total absence of dissolved oxygen in water.
Anoxia Volume-Day: A unit that represents a cubic meter of water which has
a daily mean dissolved oxygen concentration less than 1.0 mg/1. Used as a metric
of annual anoxia in the Bay when the anoxic volume of each day of the June
to October season is summed.
Atmospheric Deposition: The accretion of chemicals including nitrogen and
phosphorus attached to dust materials during dry weather or as part of raindrops
during wet weather, which deposit onto the land or water surfaces from the air.
Baseline Loading: The mass of nutrients (measured in pounds or kilograms)
which is delivered to the Bay from the basin, under the conditions of population,
land use, and point sources in 1985. Nonpoint sources considered a part of
baseline loading were computed as the average of loads washed from the land
surface by storms and river flows monitored in 1984 through 1987.
Best Management Practices (BMPs): Pollution control techniques developed
by farmers, scientists and administrators for managing nonpoint source nutrient
discharges into the Bay and its tributaries. BMPs cover two broad areas of
management: constructing facilities to contain nutrients, and employing farming
practices that decrease the use and/or runoff of fertilizers and manure.
Biological Nutrient Removal (BNR): Wastewater treatment processes that (1)
create specific biological environments which enhance phosphorus removal; and,
(2) utilize chemical energy drawn from the wastewater itself to remove nitrogen.
Biochemical Oxygen Demand (BOD): A measure of the quantity of dissolved
oxygen removed from water by the metabolism of microorganisms. Excessive
BOD results in oxygen-poor water.
Blooms: Excessive growth of plankton in concentrations sufficiently dense to
cause discoloration of water and reduced light penetration.
Characterization: The process of bringing together a number of information
sources to synthesize overall patterns or make a statement of current conditions.
Chesapeake Bay Program: The ongoing restoration and protection program
for the Chesapeake Bay conducted through the cooperation of Pennsylvania,
Maryland, Virginia, the District of Columbia, federal agencies, and the Chesa-
peake Bay Commission consisting of legislators, the governors and citizens from
the three states. The Chesapeake Bay Program was established with the historic
signing of the 1983 Chesapeake Bay Agreement.
59
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Progress Report of the Baywide Nutrient Reduction Reevaluation
Chesapeake Executive Council: Composed of the governors of Pennsylvania,
Maryland, and Virginia, the mayor of the District of Columbia, the chairperson
of the Chesapeake Bay Commission, and the Administrator of the U.S. Environ-
mental Protection Agency. The Council establishes the policy direction for the
restoration and protection of the Chesapeake Bay and its living resources.
Chlorophyll: Green pigment in plants that is essential for photosynthesis. One
type of the pigment (chlorophyll a) is commonly used as a measure of phyto-
plankton abundance.
Compliance: Conformance to the rules and regulations regarding wastewater
discharges into the Bay and its tributaries.
Conservation Tillage: In agriculture, the utilization of a tillage system appro-
priate for the soil properties, climate, and farming system that is also compatible
with the goals of reduced soil erosion and effective nutrient application.
Control Program: The methods used to reduce nutrient releases from both point
sources and nonpoint sources into the Bay and its tributaries.
Controllable: Those sources of nutrients that arise or result from the impact
of human activities and are not attributable to background loads. "Controllable"
does not imply that these loads are scheduled for control or that they can all be
managed, only that they can be controlled given the technologies available. When
the term was defined in the Nutrient Reduction Strategy arising from the 1987
Chesapeake Bay Agreement, neither atmospheric sources of nitrogen nor land-
based sources outside of Chesapeake Bay Program states were considered in this
definition though they may be amenable to control.
Conventional Pollutants: Pollutants typically discharged by municipal sewage
treatment plants and a number of industries. The category includes wastes with
a high biochemical oxygen demand (BOD), total suspended solids, fecal coliform,
pH, and grease and oil.
Dissolved Oxygen (DO): Concentration of oxygen in water, commonly em-
ployed as a measure of water quality. Low levels adversely affect aquatic life.
Most finfish cannot survive when DO falls below 3 mg/1 for a sustained period
of time.
Ecosystem: An ecological community consisting of living organisms and their
physical and chemical environment.
Effluent: Discharge or emission of a liquid or gas into the environment.
Estuary: A semi-enclosed body of water, connected to the open sea, in which
sea water is measurably diluted with fresh water from inland sources.
Fall Line: Area in a tributary where tidal waters meet free-flowing fresh water,
often called the "head of tide." In the Chesapeake Bay watershed, the fall line
marks the boundary between older, resistant rocks of the Piedmont and younger
sediments of the Coastal Plain. This is a transition zone at which water quality
is most easily related to the rate of river flow.
csc.ims.t2/91
60
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Glossary
Forest Background Loads: The mass of nutrients (measured in pounds or
kilograms) which would be delivered to the Bay from the basin if the basin were
entirely covered in forest. The forest background loads provide a metric to
establish controllable loads.
Ground Water: Subsurface water saturating soil or porous rock which often
returns, with its nitrogen loads, to surface streams during dry periods.
Habitat Requirements: The habitat and water quality restoration goals neces-
sary to promote life in and on the Bay.
Hydrodynamic: The motion of the Bay's water, brought about by wind, tide,
and density differences. The 3-D Model contains a Hydrodynamic Component
which simulates this motion.
Hypoxia: Low levels of dissolved oxygen in water, defined as less than 2 nig/
1.
Implementation Committee (IC): Composed of representatives from the
signatories to the 1983 Chesapeake Bay Agreement as well as from other federal
agencies, the IC is responsible for implementing the policy decisions and tech-
nical studies of the Chesapeake Executive Council and for coordinating the
restoration and protection activities under the 1987 Chesapeake Bay Agreement.
Light Attenuation: A measure of how quickly light disappears with increasing
depth in the water. Low light attenuation means increased levels of light penetrate
further down in the water column; also see water clarity.
Living Resources: The plant and animal life of the Chesapeake Bay.
Loading: Quantity of contaminants, nutrients, or other substances introduced
to a water body.
Mainstem: The deep mid-channel forming the longitudinal axis of the Bay from
the Susquehanna Flats to the Virginia capes. It does not include lower reaches
of the Bay's tributaries.
Marine: Pertaining to the ocean or sea.
Mesohaline: Water of medium salinity—5 to 18 parts per thousand.
Meteorological Conditions: Atmospheric phenomena, such as precipitation,
wind, and temperature which ultimately drive the surface and ground water flow
of water and nutrients.
Model: A simplified mathematical representation of reality. Water quality
modeling is used to study Chesapeake Bay processes and project effects of varying
environmental conditions or management actions.
Monitoring: Observing, tracking or measuring some aspect of the environment
to establish base line conditions and short or long-term trends.
61
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Progress Report of the Baywide Nutrient Reduction Reevatuation
Nitrogen: A nutrient essential for life. May be organic or inorganic (ammonia,
nitrate, nitrite). Elemental nitrogen constitutes 78 percent of the atmosphere by
volume.
Nonpoint Source Pollution: Toxicants, other contaminants, nutrients, or soil
entering a water body from sources other than discrete discharges such as pipes.
Includes pollution on the land which originates as atmospheric deposition as well
as farm and urban runoff.
NPDES Permits: National Pollutant Discharge Elimination System Permits to
discharge treated wastewaters to the waters of the United States issued by either
the EPA or the state.
Nutrient Enrichment: Nutrient enrichment increases primary productivity in
a water body, resulting eventually in depletion of dissolved oxygen essential to
aquatic life (also called eutrophication).
Nutrient Flux: The rate of transfer of nutrients across a surface, usually the
sediment/water column interface.
Nutrients: Chemicals required for growth and reproduction of plants. Excessive
levels of the nutrients nitrogen and phosphorus can lead to excessive algae growth.
Ocean Boundary: The interface between the Bay and the ocean. In the 3-D
Model, it represents the spatial limit of the model's extent.
Oligohaline: Water of low salinity—0.5 to 5.0 parts per thousand.
Phosphorus: A nutrient essential for life found in both organic and inorganic
forms.
Phytoplankton: Microscopic plants that live in water such as algae.
Point Source Pollution: Contamination from waste effluent discharged into a
water body through pipes or conduits.
Polyhaline: Water with a salinity of 18 to 30 parts per thousand, generally the
highest concentrations found in the Bay.
Runoff: Drainage of precipitation over the soil or a non-porous surface (e.g.,
asphalt) to a stream, river, or other receiving body of water.
Salinity: Amount, by weight, of dissolved salts in 1,000 units of water (reported
as parts per thousand).
Sediments: The loose solids, (e.g. soil from erosion or runoff), that settle to the
bottom of the Bay or its tributaries and which can be sources of nitrogen and
phosphorus.
Signatories: Representatives of Pennsylvania, Maryland and Virginia, the
District of Columbia, the Chesapeake Bay Commission, and the U.S. Environ-
mental Protection Agency who signed the Chesapeake Bay Agreements of 1983
and 1987 and are directing the Bay restoration and protection program.
CSC.LA1B.I2A1
62
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Glossary
Significant Noncompliance (SNC): Includes instances of NPDES permit vio-
lations (e.g. monthly average permit limits) or violation of administrative or
judicial orders that meet certain screening criteria for frequency and duration.
Permit holders on SNC lists are targeted first for enforcement actions.
Stratification: In Chesapeake Bay, the layering of fresh water over salt water
due to differences in relative density and temperature.
Submerged Aquatic Vegetation (SAV): Vegetation that grows underwater along
the fringes and in the shallows of the Bay.
Subpycnocline Water: The Bay's water column is separated by a natural
boundary, the pycnocline, into a fresher less dense surface layer and a more dense
saltier lower layer ("subpycnocline water") where dissolved oxygen is lower or
absent especially during the summer.
Tributary: A stream or river which joins and feeds into a larger stream, river
or other body of water.
T\irbidity: Reduction of water clarity caused by suspended sediments and
organics in the water.
Wastewater Treatment: Processes to remove pollutants, commonly categorized
as primary, secondary, and advanced levels of treatment.
Water Clarity: A general term which describes the transparency of water in
an aquatic system. Water clarity is reduced with increased amounts of particulate
materials (e.g., suspended sediments) in the water column; also see light attenu-
ation.
Water Column: A vertical extent of water reaching from the surface to the bottom
substrate of a water body.
Water quality: Status or condition of a water body in terms of defined variables
characterizing the "health" of the water.
Watershed: Area drained by a river system or other water body.
Zooplankton: Animal plankton of widely varying size that drift or swim weakly
in the water. They consume the primary producers and are a second link in the
food chain or food web.
63
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References
REFERENCES
1. Chesapeake Bay Program: Findings and Recommendations. U.S. Envi-
ronmental Protection Agency, Region III, Chesapeake Bay Program. Philadel-
phia, Pennsylvania. September 1983. 54 pages.
2. Chesapeake Bay: A Framework for Action. U.S. Environmental Protection
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