tmdls and statistical models kenneth h. reckhow duke university
TRANSCRIPT
TMDLs and Statistical Models
Kenneth H. Reckhow
Duke University
TMDL Applications
Forecast and establish initial pollutant allocation
Forecasting
The problem with water quality forecasting is that we’re not terribly good at it.
Result: prediction uncertainty is high
N Reductions Relative to 1991-95
0
5
10
15
20
25
-70-60-50-40-30-20-100
Sta
ndar
d V
iola
tions
(%
)
90% Predictive Interval90% Predictive Interval
““Margin of Safety”Margin of Safety”
Target ReductionTarget Reductionwith 95% Confidencewith 95% Confidence
TMDL Applications
Forecast and establish initial pollutant allocation
Update and modify through adaptive implementation
• TMDLs should be adaptive
TMDL Implementation
• Modeling approaches need to be developed that integrate model forecasts with post-implementation monitoring (e.g., Bayesian analysis, Kalman filter, data assimilation).
Prior (model forecast)
Sample(monitoringData)
Posterior (integrating modelingand monitoring)
Adaptive Implementation: Bayesian Analysis
Criterion Concentration
Bayes (Probability) Networks
Conditional probability models that can be mechanistic, statistical, judgmental use probability to express uncertainty use Bayes theorem for adaptive implementation updating.
Oxygen is Oxygen is depleteddepleted in in the bottom the bottom
water.water.
Oxygen is Oxygen is depleteddepleted in in the bottom the bottom
water.water.
Algae die and Algae die and accumulateaccumulate on the bottom where they on the bottom where they are are consumedconsumed by bacteria. by bacteria.
Algae die and Algae die and accumulateaccumulate on the bottom where they on the bottom where they are are consumedconsumed by bacteria. by bacteria.
Under calm wind Under calm wind conditions, density conditions, density
stratificationstratification occurs.occurs.
Under calm wind Under calm wind conditions, density conditions, density
stratificationstratification occurs.occurs.
Nitrogen Nitrogen stimulatesstimulates the growth of algae.the growth of algae.
Nitrogen Nitrogen stimulatesstimulates the growth of algae.the growth of algae.
Fish and Fish and shellfish may shellfish may diedie
or become or become weakened weakened and and vulnerable to vulnerable to
disease.disease.
Fish and Fish and shellfish may shellfish may diedie
or become or become weakened weakened and and vulnerable to vulnerable to
disease.disease.
The Negative Effects of Excessive
Nitrogen inan Estuary
The Negative Effects of Excessive
Nitrogen inan Estuary
NitrogenInputs Cause and Effect
RelationshipsCause and Effect
Relationships
Frequency of Hypoxia
Duration of Stratification
HarmfulAlgal Blooms
Carbon Production
SedimentOxygenDemand
RiverFlow
AlgalDensity
ChlorophyllViolations
Number ofFishkills
FishHealth
ShellfishAbundance
SedimentOxygenDemand
Duration of Stratification
RiverFlow
AlgalDensity
Carbon Production
Frequency of Hypoxia
Cross-System Cross-System ComparisonComparison
Simple Simple MechanisticMechanistic
Expert Expert ElicitationElicitation
Number ofFishkills
NitrogenInputs
FishHealth
ChlorophyllViolations
HarmfulAlgal Blooms
ShellfishAbundance
Empirical ModelEmpirical Model
Seasonal RegressionSeasonal Regression
Site-Specific ApplicationSite-Specific Application
Survival ModelSurvival Model
Research Opportunities
This would allow more accurate assessment of the effectiveness of NPS controls, and targeting of BMP improvements.
With SPARROW linked to a waterbody model, post-implementation monitoring could be designed for Bayesian updating.