Post on 12-Oct-2020
Bay TMDL 101Gary Shenk
CBPO
2017 01 06
1
New Targets are Nothing ‘New’
Year Model Phase Goal
• 1987 0 40% reduction
• 1992 2 40% of controllable loads
• 1997 4.1 Confirm 1992 loads
• 2003 4.3 Reallocation
• 2010 5.3.0 TMDL
• 2011 5.3.2 Phase 2 WIP targets
• 2017 6.0 Phase 3 WIP targets
2
TMDL Timeline
• 1999 – Lawsuit by American Canoe Association and American Littoral Society
• 2010 – TMDL put in place, Phase I WIPs completed
• 2011 – 2 updates to Watershed Model, Phase II WIPs completed
• 2017 MidPoint Assessment• 60% of the management practices implemented
• Improved models
• Mid-Course Correction?
• 2025 TMDL Goal Date• 100% of the management practices implemented
3
Chesapeake Bay TMDL
Necessitated by failure to meet water quality standards
4
Decision Support System
0
10
20
30
40
50
60
70
80
90
100
0 10 20 30 40 50 60 70 80 90 100
Percent of Space
Perc
ent
of T
ime
CFD Curve
Area of Criteria
Exceedence
Area of Allowable
Criteria
Exceedence
0
10
20
30
40
50
60
70
80
90
100
0 10 20 30 40 50 60 70 80 90 100
Percent of Space
Perc
ent
of T
ime
CFD Curve
Area of Criteria
Exceedence
Area of Allowable
Criteria
Exceedence
Data
Watershed Model
Bay Model
CriteriaAssessmentProcedures
Effects
Allocations
AirshedModel
Land UseChange Model
5
6
Chesapeake Bay Partnership Models
7
Chesapeake Bay Partnership Models
Bay Dissolved Oxygen Criteria
Minimum Amount of Oxygen (mg/L) Needed to Survive by Species
Migratory Fish Spawning & Nursery Areas
Hard Clams: 5
Striped Bass: 5-6
Worms: 1
Shallow and Open Water Areas
Deep Water
Deep Channel
6
5
3
2
1
4
0
Crabs: 3
Spot: 2
White Perch: 5
American Shad: 5
Yellow Perch: 5
Alewife: 3.6
Bay Anchovy: 3
8
Rockfish, BluefishMenhaden Habitat
Shad, Herring, Perch and Rockfish Spawning Habitat
Local “Zoning” for Bay and Tidal River Fish, Crab and Grasses Habitats
Bay GrassesHabitat
Oyster, Crab, Croaker and SpotHabitat
Summertime Crab Food Habitat
Redefined ‘swimmable/fishable’ in terms the public could relate to9
Rockfish, BluefishMenhaden Habitat
Local “Zoning” for Bay and Tidal River Fish, Crab and Grasses Habitats
Oyster, Crab, Croaker and SpotHabitat
Summertime Crab Food Habitat
Redefined ‘swimmable/fishable’ in terms the public could relate to
1 mg/l Oxygen
3 mg/l Oxygen
5 mg/l Oxygen
10
An Assessment of Dissolved Oxygen Criteria
Spatial Extent of Low Oxygen =>
Tem
po
ral E
xten
t o
f Lo
w O
xyge
n =
>
11
An Assessment of Dissolved Oxygen Criteria
Spatial Extent of Low Oxygen =>
Tem
po
ral E
xten
t o
f Lo
w O
xyge
n =
>
12
Curve representative of an acceptable level of Oxygen
Test curve for a particular deep water segment
An Assessment of Dissolved Oxygen Criteria
Spatial Extent of Low Oxygen =>
Tem
po
ral E
xten
t o
f Lo
w O
xyge
n =
>
13
Red area = unallowable exceedance
‘Stoplight’ Table
Deep Water Attainment
Cbseg Base Draft Allocation E3
CB3MH 2.5% 0.1% 0.0%
CB4MH 23.3% 3.8% 1.5%
CB5MH 5.3% 0.0% 0.0%
CB6PH 0.6% 0.0% 0.0%
CB7PH 0.4% 0.0% 0.0%
CHSMH 5.5% 0.0% 0.0%
EASMH 3.3% 0.0% 0.0%
Calculated January 200914
Critical Period 1993-1995
• Stoplight tables are calculated over a 3-year period
• Regulations require that ‘critical conditions’ be determined where variable environmental factors make attainment more difficult
• Often interpreted as a ‘once in 10 years’ event
• 1993–1995 selected for stream flows with a 10-year return. • 1996-1998 was more extreme
• Choice of the critical period affects the overall effort required to meet the TMDL
15
Hydrologic Averaging Period 1991-2000
• Loads from the watershed model are based on the weather during the hydrologic averaging period
• Wetter periods would show more load from nonpoint source
• Dryer periods would show more load from point source
• Any 10-year period is representative, 1991-2000 chosen as • slightly more representative
• Includes the critical period
• Choice of hydrologic averaging period affects point/nonpoint balance.
16
TMDL Allocation Calculation
17
•Areas that contribute the most to the problem must do the most to resolve the problem.
•All tracked and reported reductions in nutrient loads are credited toward achieving final assigned loads.
•Allocated N and P loads must result in attainment of water quality standards
Guidelines for Allocations
18
•Areas that contribute the most to the problem must do the most to resolve the problem.
•All tracked and reported reductions in nutrient loads are credited toward achieving final assigned loads.
•Allocated N and P loads must result in attainment of water quality standards
Guidelines for Allocations
19
0
5
10
15
20
25
30
35
40
45
1985 Base 2009 Target Tributary Loading Loading Loading E3 All
Scenario Calibration Scenario Load A Strategy Scenario Scenario Scenario Scenario Forest
342TN 309TN 248TN 200TN 191TN 190TN 179TN 170TN 141TN 58TN
24.1TP 19.5TP 16.6TP 15.0TP 14.4TP 12.7TP 12.0TP 11.3TP 8.5TP 4.4TP
Nu
mb
er
of
Seg
men
ts in
DO
Vio
lati
on
Open Water Violations
Deep Water Violations
Deep Channel Violations
Dissolved Oxygen Criteria Attainment
Basin-wide load is190 N and 12.7 P (MPY)
20
•Areas that contribute the most to the problem must do the most to resolve the problem.
•All tracked and reported reductions in nutrient loads are credited toward achieving final assigned loads.
•Allocated N and P loads must result in attainment of water quality standards
Guidelines for Allocations
21
Determining Who Contributes the MostKey factors:
Distance from Tidal water • Riverine transport
Position along mainstem bay• Estuarine circulation
Existence of riverine estuary
Riverine delivery:Pound delivered per pound produced
Estuarine deliveryOxygen reduced per pound delivered
Overall EffectivenessOxygen reduced per pound produced
22
23
Relative Effect of a Pound of Pollution on Bay Water Quality
24
Relative effectiveness (Riverine * Estuarine Delivery)
0
1
2
3
4
5
6
7
8
UpE
S, M
DU
pES,
DE
Mid
ES, M
DSu
sq, M
DLo
wES
, MD
Wsh
, MD
UpE
S, P
ALo
wES
, DE
Susq
, PA
PxtB
, MD
EshV
A, V
APo
tB, D
CM
idES
, DE
PotA
, DC
PotB
, MD
PotB
, VA
Susq
, NY
Rap
B, V
APo
tA, M
DYr
kB, V
APo
tA, V
AW
sh, P
APo
tA, W
VPo
tA, P
APx
tA, M
DJm
sB, V
AR
apA
, VA
YrkA
, VA
JmsA
, VA
JmsA
, WV
Major River Basin by Jurisdiction Relative Impact on Bay Water Quality
•Areas that contribute the most to the problem must do the most to resolve the problem.
•All tracked and reported reductions in nutrient loads are credited toward achieving final assigned loads.
•Allocated N and P loads must result in attainment of water quality standards
Guidelines for Allocations
25
Accounting for Previous Reductions
•An allocation method that requires all states to make a similar effort from here on out would disadvantage states that have already done more.
•Require a percentage of the way between:• No Action: no BMPs, low level of WWTP• Everyone, Everything, Everywhere (E3)
26
27
TN, p5.3, goal=190, WWTP = 4.5-8 mg/l, other: max=min+20%
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 1 2 3 4 5 6 7 8 9 10
Relative Effectiveness
Pe
rce
nt
red
uc
tio
n f
rom
20
10
no
BM
Ps
to
E3
All Other
WWTP
4.5 mg/l
8 mg/l
20 percent slope
Allocation Method Agreed to by Majority of Principals’ Staff
Committee Members
Wastewater Loads
All other sources
TP, p5.3, goal=12.67 WWTP = .22 - .54 mg/l, other: max=min+20%,
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
0 1 2 3 4 5 6 7 8 9 10
Relative Effectiveness
Pe
rce
nt
red
uc
tio
n f
rom
20
10
no
BM
Ps
to
E3
All Other
WWTP
1. Plot effectiveness vs percent effort2. Use 2010 as the base year3. Set upper half of WWTP line at 3 mg/l equivalent; intercept at 8 mg/l4. Most effective basin is 20 percentage points higher than least effective
28
29
5. Add special cases
30
State/basin allocations (N/P (MPY))
Changing No Action and E3 Year - Theoretical
31
Allocation = 140Both basins are the same percent of the difference between NA and E3
2010 2010
Changing No Action and E3 Year - Theoretical
32
Allocation = 140Both basins are the same percent of the difference between NA and E3
2010 2010 2012 2012
Changing No Action and E3 Year - Theoretical
33
Allocation = 140Both basins are the same percent of the difference between NA and E3
2010 2010 2012 2012 2017 2017
TN Allocation Percent of Base Year 2010
0%
20%
40%
60%
80%
100%
120%
PA MD VA NY WV DE DC
Pe
rcen
t o
f a
llo
ca
tio
n u
sin
g 2
01
0
BY 2010
BY 2002
BY 1985
34
2009 WQGIT presentationTN Allocation Relative to using 2010 for No Action and E3
35
Allocation Percent of Base Year 2010 TP
0%
20%
40%
60%
80%
100%
120%
140%
PA MD VA NY WV DE DC
Pe
rcen
t o
f a
llo
ca
tio
n u
sin
g 2
01
0
BY 2010
BY 2002
BY 1985
TP Allocation Relative to using 2010 for No Action and E3
36
State/basin allocations (N/P (MPY))
Phase I WIPs developed to meet these numbers
Scenario Year for WIP Development
• Once load targets are established jurisdictions develop WIPs to meet those loads in the watershed model.
• To generate the loads, the partnership must choose a scenario year to estimate the available land for BMP implementation, the human and animal populations, agricultural systems, etc.
• Choosing a current year answers the question: “What BMPs are needed to meet the goals given the current state of the watershed”.• Future growth might be handled through offsets
• Choosing a future year answers the question: “What BMPs are needed to meet the goals given the projected state of the watershed”.• Future growth might already be included
• 2010 was chosen for Phase I and Phase II WIPs
37
Phase II WIPs - 2011
• 2010 TMDL based on Phase 5.3 watershed model
• Partnership requested changes to Phase 5.3 during 2010• Land use
• Nutrient Management
• Phase I WIPs (plus small adjustments to meet WQS) were run on the Phase 5.3.2 watershed model to generate planning targets• Consistent with the 2010 TMDL
• Numbers were different but represented the same level of effort
• Phase II WIPs were developed to meet the planning targets.
38
150
175
200
225
250
275
2009 2011 2013 2015 2017 2019 2021 2023 2025
De
liv
ere
d N
Lo
ad
s (
mil
lb
s/y
r)
Assumes Constant Reduction Over Time
Interim Target: 60% by
2017
Two-Year Milestones and 2017
39
Planning Target
StartingPoint
Phase III WIPs and Planning Targets
40
Target Method
Changes
• New Watershed Model Loads• Higher coastal plain loads
• Change in seasonality
• New Estuarine Model• Biogeochemical changes
• Wetland and shoreline
• Climate Change
41
Changes
• New Watershed Model• Change in delivery factors
• New Estuarine Model• Biogeochemical changes
42
Changes
• New Watershed Model• Definition of E3
• Effectiveness of BMPs
• Loading rate of land uses
43
Default Target Method
• Plot effectiveness vs percent effort
• Use 2010 as the base year
• Set upper half of WWTP line at 3 mg/l equivalent; intercept at 8 mg/l
• Most effective basin is 20 percentage points higher than least effective for ‘all other’ line
• Special cases
• Hydro Period
• Critical Period
• Conowingo
• Climate Change
44
Special Request Topics
• How are we doing relative to the WWTP hockey stick?
• Why does historical data matter?
• What about monitoring trends?
45
46
Draft values – for WQGIT discussion purposes
Differences reflect jurisdictional choices on the source of reductions
47
Draft values – for WQGIT discussion purposes
Differences reflect jurisdictional choices on the source of reductions
Historical Data Matters
48
Critical Period 1993-1995
One way to understand the TMDL question:How much more do we need to implement in addition to what was already on the ground in the early 1990s to meet water quality standards
Historical Cleanup
• A lack of historical data during the calibration period (1985-2013) will result in a calibrated Phase 6 Model which does not accurately account for the effect of changes in implementation.
• However, states will have the opportunity to update their Phase 6 historical record each year as part of reporting progress to NEIEN.
• Accurate revisions to historical data will be beneficial in assessing progress during each progress year and milestone period.
49
Monitoring Trends
• As currently formulated, monitoring trends are not part of the formula for calculating planning targets.
• Monitoring concentrations and estimated loads are used in the calibration of the models.
• Monitoring generates new knowledge about the watershed which is incorporated into decision tools.• Conowingo
• Phosphorus
• Other Explaining Trends work
• Monitoring can be used to inform jurisdictional choices. For example: • Move implementation to areas where loads are climbing
• Move implementation to areas with shorter lag times
50
Role of Monitoring
51From Scott Phillips, USGS