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Transcript of Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented...
![Page 1: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/1.jpg)
Ammonia Toxicity ModelAMMTOX
Training Session Held 5 Dec 2005
Hosted by EPA Region VIII
Presented by Jim Saunders,
Colorado WQCD
![Page 2: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/2.jpg)
Purpose of Training Session
• Explain rationale for model
• Identify data needs and sources, including options for use of site-specific data
• Demonstrate operation of model
• Work with test data sets
![Page 3: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/3.jpg)
Assumptions and Disclaimers
• Familiarity with Excel is assumed
• VB programming is NOT covered
• Future tech support is not my job
• Merits of National Criteria are not open for discussion
• Ideas and suggestions presented in this session may not conform to policies of state or federal permitting agencies
![Page 4: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/4.jpg)
Section 1: Concepts and Construction
Central Question:Where is there greatest risk of exceeding
stream standard?
Depends on pollutant behavior and control of toxicity
![Page 5: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/5.jpg)
Location of Controlling Conditions
Control of Toxicity
Control of Concentration
Concentration + pH & Temp
Conservative Outfall Downstream, simple
Non-conservative Outfall Downstream, complex
![Page 6: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/6.jpg)
How do you handle a problem like Ammonia?
• Calculating permit limits becomes difficult when controlling conditions are displaced downstream
• Good news: solution likely to benefit discharger
![Page 7: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/7.jpg)
0
1
2
3
4
5
6
7
8
9
0 2 4 6 8 10
Miles below Outfall
pH
05101520253035404550
Acu
te S
tan
dar
d,
mg
/L
pH Acute Standard
Pattern of Toxicity, Simple Scenario• Initial
– pH: 6.6– Temp: 16.3
• Final– pH: 8.0– Temp: 10
• Rebound– pH: 0.2/mi– Temp: 0.7/mi
0
2
4
6
8
10
12
14
16
18
0 2 4 6 8 10
Miles below Outfall
Tem
per
atu
re o
r p
H
012345678910
Ch
ron
ic S
tan
dar
d,
mg
/L
pH Temperature Chronic Standard
![Page 8: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/8.jpg)
Pattern of Toxicity, Complex Scenario
• Simple Scenario pH, temperature
• Initial ammonia = 5.5
• Loss = 3/d• V= 2 fps
0
1
2
3
4
5
6
7
0 2 4 6 8 10
Miles below Outfall
Am
mo
nia
Co
nce
ntr
atio
n,
mg
/L
Chronic Standard Ammonia
![Page 9: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/9.jpg)
Required Tasks
• Define d/s trajectory of stream standard
• Define d/s trajectory of ammonia concentration
• Determine maximum effluent concentration such that instream ammonia will not exceed standard at any point downstream
![Page 10: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/10.jpg)
Trajectory of Standard
• Effect of effluent on stream chemistry generally elevates standard
• Effect is transitory
• Initial value of standard declines downstream because underlying controls (pH and temperature) trend separately toward “equilibrium” values
• Greatest risk of exceedance may occur anywhere between outfall and equilibrium conditions
![Page 11: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/11.jpg)
What is equilibrium?
• Stable pH and temperature characteristic of this mixture of effluent and stream water
• May differ from upstream conditions, especially if effluent flow is large
• Equilibrium is dynamic with substantial diel and seasonal variation in pH and temperature
• This variability must be captured in standard
![Page 12: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/12.jpg)
Trajectories for pH and Temperature
• Initial mixed conditions defined from flow-weighted mean pH and temperature
• Effect of effluent on stream pH and temperature is transitory
• Initial mixed pH and temperature trend separately toward “equilibrium” values
• If the equilibrium value and the rate of change are known, pH or temperature can be predicted at any point downstream of the outfall
![Page 13: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/13.jpg)
Setpoint: Equilibrium with Regulatory Twist
• pH and temperature associated with greatest risk of exceeding ammonia standard for equilibrium conditions
• Worst case in each month, subject to once-in-three-year exceedance
• Terminus for pH and temperature trajectories, not a fixed location
![Page 14: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/14.jpg)
Why Obtaining Setpoint is Difficult
• Sole task of Recur model• Field grab samples form framework• Apply characteristics of temporal variation to
construct set of hourly values spanning entire period of record
• Calculate standards hourly and determine acute (1-h) and chronic (30-d) values consistent with once-in-three-year exceedance threshold
• Find associated pH (acute and chronic) and temperature (chronic)
![Page 15: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/15.jpg)
Application for Setpoint
• Hidden hand – guides pH and temperature toward target with regulatory meaning
• Essential for producing d/s trajectory of ammonia standard, separately for acute and chronic
![Page 16: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/16.jpg)
Back up a step....Incorporation of temporal variation
• pH and temperature in stream exhibit temporal variation of diel and seasonal scales...thus applies to standard, too
• Predictable diel pattern– Based on sine curve– Given amplitude and time of max, one grab
value can define complete 24-h pattern– Model contains defaults, or user can supply
![Page 17: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/17.jpg)
Diel Patterns of Variation
• Pattern of each is predictable (sine curve)
• Asynchronous pH and temperature patterns
0
2
4
6
8
10
12
14
16
18
00:00 04:00 08:00 12:00 16:00 20:00 00:00
Tem
pera
ture
, o
C
7.0
7.2
7.4
7.6
7.8
8.0
8.2
8.4
8.6
8.8
9.0
pH
Temperature pH
![Page 18: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/18.jpg)
Adjusting Grab Sample Data
• Translate grab sample to daily average or maximum using amplitude and time of maximum
Daily Mean
Daily Maximum
Grab Sample
Amplitude
0
1
2
3
4
5
6
7
8
9
10
0:00 6:00 12:00 18:00 0:00
Time of Day
Pre
dic
ted
Te
mp
era
ture
![Page 19: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/19.jpg)
Implications for Toxicity
• Time of day matters
• Not a sine function
• Average toxicity is not same as toxicity based on average pH and temperature 0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
0:00 4:00 8:00 12:00 16:00 20:00 0:00
Time of Day
pH
-dep
end
ent
Co
mp
on
ent
![Page 20: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/20.jpg)
Empirical Seasonal Pattern
• Driven by pattern observed in recent historical record
• Temperature shows strong seasonal variation in mean; tracking air temperature
• pH shows strong seasonal variation in amplitude; result of biological activity
![Page 21: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/21.jpg)
Seasonal Variation: Temperature
• Strong pattern• Monthly time step• Importance of
physical processes
0
5
10
15
20
25
30
Oct-92 Jul-93 Apr-94 Jan-95
Tem
per
atu
re,
oC
Max Min
![Page 22: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/22.jpg)
Seasonal Variation: pH
• Seasonal change in maxima, but not in minima
• Amplitude varies across sites in same region
• Importance of biological processes
South Platte at Englewood
7.0
7.5
8.0
8.5
9.0
9.5
Dec-00 Apr-01 Jul-01 Oct-01 Jan-02 May-02
pH
Daily Max Daily Min
![Page 23: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/23.jpg)
Next Task: Ammonia Trajectory
• Initial concentration determined by mass balance calculations
• Change in concentration d/s affected strongly by biological processes (i.e., non-conservative behavior)
• Dominant process: nitrification
• Others: uptake (-), ammonification (+)
• Model represents a net loss rate
![Page 24: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/24.jpg)
Why Non-conservative Matters
• Nitrification reduces ammonia
• First order kinetics
• Any loss increases limits
0%10%20%
30%40%50%60%70%
80%90%
100%
0.0 0.5 1.0 1.5 2.0
Time, days
Am
mo
nia
Rem
ain
ing
K3=1 K3=2 K3=4 K3=8
![Page 25: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/25.jpg)
K3 Temperature Dependence
• Nominal rate applies at 20oC• Ambient rate sensitive to temperature (8%/oC)
0
5
10
15
20
25
30
0 5 10 15 20 25 30
Stream Temperature, oC
Am
bie
nt
K3,
per
day
K3=6 K3=2 K3=12
![Page 26: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/26.jpg)
Revisit Scenario with New K3
• Interaction of loss rate and d/s trajectory of standard• Importance of site-specific data
0
1
2
3
4
5
6
7
0 2 4 6 8 10
Miles below Outfall
Am
mo
nia
Co
nce
ntr
atio
n,
mg
/L
Chronic Standard Ammonia (K3=3) Ammonia (K3=6)
![Page 27: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/27.jpg)
Next Task: Linking Limits to Standards
• AMMTOX sets monthly limits by manual iteration (i.e., trial and error)
• Aiming for maximum effluent concentration such that instream ammonia will not exceed standard at any point downstream
![Page 28: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/28.jpg)
Trial Iteration
0
1
2
3
4
5
6
7
0 2 4 6 8 10
Miles below Outfall
Am
mo
nia
Co
nce
ntr
atio
n,
mg
/L
Chronic Standard Ammonia (Co=5.5) Ammonia (Co=4.5)
![Page 29: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/29.jpg)
Organization of AMMTOX
• Recurrence model– Defines setpoint conditions, integral to
mapping downstream trajectory of toxicity
• Reach Model– Predicts downstream pattern of stream
standard based on expected spatial patterns in pH and temperature
– Predicts downstream changes in total ammonia based on first order kinetics
– Employs graphical approach for setting permit limits
![Page 30: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/30.jpg)
Section 2: Data Needs and Sources
• Setpoint Determination– Grab samples from equilibrium stream
conditions; 3-5 yrs, weekly-monthly– Diel patterns of variation for pH and
temperature (amplitude, time of max)• Default (3 levels for pH)• User supplied (confirm or replace default)
– Ecological Conditions• Implied by classification (warm vs. cold)• Local knowledge of fish community
![Page 31: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/31.jpg)
Sampling Site Selection
• Ideal site: far enough downstream for rebound to be complete, yet not influenced by tributaries, etc.
• Practical site– Upstream OK if too many confounding
influences downstream– Small effluent: upstream or 2-4 mi downstream– Large effluent: trajectory based on interim sites
![Page 32: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/32.jpg)
Site-Specific Characterization of Diel Patterns of Variation
• Summer (July-August best)
• Low flow
• Data logger: 15-min intervals; get amplitude and time of max
• Grab: sunrise for minima, mid- to late afternoon for maxima; get amplitude
• With either approach, a few sunny days will determine usefulness of defaults
![Page 33: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/33.jpg)
0
100
200
300
400
500
600
700
6:00 18:00 6:00 18:00 6:00
Time of Day
Su
nlig
ht,
W/m
2
7.6
7.8
8.0
8.2
8.4
8.6
8.8
9.0
pH
Light pH
Sunny Days and pH Amplitude
![Page 34: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/34.jpg)
Sampling Time and Default Amplitude
7.20
7.40
7.60
7.80
8.00
8.20
8.40
00:00 06:00 12:00 18:00 00:00
Low Medium High
![Page 35: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/35.jpg)
Define Ecological Setting for Reach Model
• Are salmonids present?– Default assumption might be yes for Cold
water classification– Affects pH component (applies to acute and
chronic standards)
• Are Early Life Stages (ELS) present?– Must specify for each month– Applies to all species in fish community– Affects temperature component (does not
apply to acute)
![Page 36: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/36.jpg)
Salmonids and Effect of FAV
0
10
20
30
40
50
60
6.5 7.0 7.5 8.0 8.5 9.0
pH
CM
C,
mg
/L
Present Absent
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Acute Values (CMC)
• 1-h average
• Nonlinear function of pH
• Not a function of temperature
• Linear function of FAV– Salmonids present: 11.23– Salmonids absent: 16.8
![Page 38: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/38.jpg)
Temperature Dependence and ELS
• T<7oC; max effect of ELS
• 7<T<14.5oC; diminishing effect
• T>14.5oC; no effect of ELS
CCC Temperature Dependence
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0 5 10 15 20 25 30
Temperature, oC
Ad
just
men
t T
erm
ELS present ELS absent
![Page 39: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/39.jpg)
Chronic Values (CCC)
• 30-d average• Nonlinear function of pH• Linear function of FAV• Nonlinear function at higher temperature
– Invertebrate slope: 10-0.028*(T-25); T>7oC
• Linear function at lower temperature– ELS absent; invertebrate GMCV (1.45)
applies at T<7– ELS present; fish GMCV (2.85) applies at
T<14.5
![Page 40: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/40.jpg)
Reach Model Inputs
• Flows
• Water Quality
• Basis for trajectories– Rebound– Setpoint– K3– Travel time
• Characteristics of standards
• Consistency with Recur Model (not linked)
![Page 41: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/41.jpg)
Hydrologic Conditions
• Upstream: Regulatory low flow (e.g., DFLOW)
• Effluent: Design capacity
• Tributaries and diversions: preserve low flow regime; reconstructions and DFLOW by difference
• Seepage: Residual between gages; includes alluvial discharge, direct surface runoff and small, ungaged tributaries
![Page 42: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/42.jpg)
Input Water Quality
• Avoid worst of worst scenarios
• Upstream: average or median
• Effluent (pH, temperature): average or median
• Seepage: average or median
• Diversions: no direct effect on WQ
![Page 43: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/43.jpg)
Rebound Rates
• Default rates used in AMMTOX– pH: 0.2 units per mile– Temperature: 0.7 oC per mile
• Site-specific rates are very rare
• Produces gradual, linear shift toward setpoint conditions
![Page 44: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/44.jpg)
Spatial Patterns of Variation
• Addition of effluent changes temperature and depresses pH in stream
• Shift is transitory, but can be dramatic
0
2
4
6
8
10
12
14
16
18
0 5 10 15
Distance, mi
Te
mp
era
ture
, oC
6.56.66.76.86.97.07.17.27.37.47.57.6
Temperature pH
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Ammonia Loss Rate
• Measured for many CO streams
• Wide range of values; generous default
• Study design considerations– Paired samples d/s of mixing zone– Travel time critical; must be able to see
change in concentration– Detection limit and resolving power– Implications for DO modeling– Dilution by seepage vs. biological decay
![Page 46: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/46.jpg)
Velocity
• Channel Geometry– Default– Site-specific: USGS Surface-water
Measurements
• Manning’s Eqn• Fixed Value; enter manually by reach• Special Considerations
– Acute and chronic can be set separately– Multiple equations or approaches can be used
when proper links are established
![Page 47: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/47.jpg)
Time of Travel
St Vrain at Lyons
y = 0.0788x0.6405
R2 = 0.989
0.1
1
10
10 100 1000
Discharge, cfs
Av
era
ge
Ve
loc
ity,
ft/
s
![Page 48: Ammonia Toxicity Model AMMTOX Training Session Held 5 Dec 2005 Hosted by EPA Region VIII Presented by Jim Saunders, Colorado WQCD.](https://reader036.fdocuments.in/reader036/viewer/2022081801/56649cc15503460f94988745/html5/thumbnails/48.jpg)
Design of Basic Sampling Program• What
– Stream: pH, temperature, time, ammonia (u/s)– Effluent: pH, temperature
• When– Stream: biweekly or monthly– Effluent: individual, not DMR summary
• Where– Upstream– Downstream (equilibrium conditions)
• Supplemental– Ammonia loss rate– Diel variation in pH and temperature– Seepage– Velocity