CASE STUDIES APPLYING EMPIRICAL APPROACHES William T. Hall Hall - - PowerPoint PPT Presentation

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CASE STUDIES APPLYING EMPIRICAL APPROACHES William T. Hall Hall - - PowerPoint PPT Presentation

Apr 11, 2024 120 likes •248 views

CASE STUDIES APPLYING EMPIRICAL APPROACHES William T. Hall Hall & Associates LINEAR REGRESSION Neshaminy Creek Periphyton Data 600 Periphyton Chl-a (mg/M 2 ) Observed 500 Dodds et al. (2002) Regression TN:TP = 12:1 400 300 R 2 =0.048

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SLIDE 1

CASE STUDIES APPLYING EMPIRICAL APPROACHES

William T. Hall Hall & Associates

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SLIDE 2

LINEAR REGRESSION

Regressions based on World/Eco-Regional Data cannot predict Site-Specific responses

Neshaminy Creek Periphyton Data 100 200 300 400 500 600 0.2 0.4 0.6 0.8 1 Total Phosphorus (mg/L) Periphyton Chl-a (mg/M2)

Observed Dodds et al. (2002) Regression TN:TP = 12:1

R2=0.048

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SITE-SPECIFIC DATA GOOSE CREEK

Goose Creek/Chester Creek Periphyton Data versus TP Concentration 100 200 300

GC-1 GC-2 GC-3 GC-4 CC-1 CC-2 CC-3 CC-4 CC-5

Station Chl-a (mg/m2) 0.0 0.5 1.0 1.5 2.0 2.5 3.0 TP (mg/L)

Chl-a Avg TP EPA Nuisance Algae Threshold

TP not causing Nuisance Periphyton Growth

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CRITICAL FACTOR IGNORED

Periphyton Chlorophyll-a versus Canopy Cover Wissahickon Creek Watershed, Pennsylvania

R2 = 0.71

50 100 150 200 250 300 350 400 10 20 30 40 50 60 70 Canopy Cover (%) Chlorophyll-a (mg/m2)

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SLIDE 5

CONDITIONAL PROBABILITY

EPT Taxa; Change Point = 38 ug/L

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CONDITIONAL PROBABILITY TP < 0.1 MG/L

Raw data scatter plot Conditional Probability Plot Change Point > 95 ug/L

0.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0

0.001 0.01 0.1 1 TP (mg/L)

EPT Taxa < 8

2 4 6 8 10 12 14 16 18 20 0.001 0.01 0.1 1 TP (mg/L) EPT Taxa

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SLIDE 7

MBSS EPT DATA ANALYSIS OF VARIANCE

5 10 15 20 25 30 35

4 - 6 7 - 8 9 - 9 10 - 10 11 - 11 12 - 12 13 - 14 15 - 16 17 - 19 20 - 24 25 - 29 30 - 39 40 - 59 61 - 97 107 - 682

O b s e r v a t io n s

2 4 6 8 10 12 14 16 18

4 - 6 7 - 8 9 - 9 10 - 10 11 - 11 12 - 12 13 - 14 15 - 16 17 - 19 20 - 24 25 - 29 30 - 39 40 - 59 61 - 97 107 - 682

Bin (TP Range - ug/L) Avg EPT

No Significant Difference; p=0.40 Significant; p=0.03

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SLIDE 8

CONDITIONAL PROBABILITY

(Riffle Diatom TSI; Change Point = 36 ug/L)

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EMAP AND NAWQA DATABASE ANALYSIS OF VARIANCE

1 2 3 4 5 6 5-21 24-36.5 37-54 60-75 77-142 >150 Bin (TP Range - ug/L) Diatom TSI

RESULTS NOT SIGNIFICANT (P=0.36)

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SLIDE 10

SITE-SPECIFIC EPT RESPONSE GOOSE CREEK

1 2 3 4 5 6 7 1983 1985 1987 1989 1991 1993 1995 1997

Year Nutrient (mg/L)

2 4 6 8 10 12 14

EPT Taxa

  • rtho Phosphate

Ammonia-N EPT Taxa EPT Impairment Threshold

No TP: Invertebrate Relationship

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SLIDE 11

PAXTON CREEK

Paxton Creek - 2007 SRBC Data Growing Season Average

0.00 0.05 0.10 0.15 0.20 0.25 1 3 2 4 5 6 7 8 9 10 11 12 HW

Station TP (mg/L)

TP Impaired Segments Sediment Impaired Segments Un-Impaired Segments

TP WQS - 0.025 mg/L

Concrete Channel

Paxton Creek - 2006-2007 SRBC Data

y = 0.10x - 4.76 R2 = 0.47

2 4 6 8 10 12 14 16 20 40 60 80 100 120 140 160 180 200

Habitat Score EPT Taxa

Habitat Impaired Sediment Impaired Un-Impaired

No TP: Impairment Relationship

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SLIDE 12

CONCLUSIONS

  • Linear Regressions inadequate

– Regional data cannot be used to represent site-specific conditions – Failure to consider site-specific data yields inappropriate conclusions

  • Conditional Probability Analysis unreliable

– Results conflict with traditional statistical evaluations – Endpoints do not reflect site-specific data; biological significance unknown