Characterizing Baseline Water Body Conditions

What?

• Confirm impairments and identify problems• Statistical summary• Spatial analysis• Temporal analysis• Stressor identification

Why?

• Lay groundwork for identification of causes and sources

• Document “before” conditions• Select and target BMPs• Support design of monitoring and evaluation

program

Confirm impairments and identify problemsCompare available monitoring data to wqs, but

go beyond 305(b) or 303(d) assessments:• Assess magnitude of the impairment

– % exceedance

• When do impairments occur?– Seasonally?– Associated with rainfall or high flows?

• Where do impairments occur?

04-Jan-9512-Apr-95

19-Jul-9530-Oct-95

07-Feb-9615-May-96

19-Aug-9616-Dec-96

31-Mar-9702-Jul-97

06-Oct-9721-Jan-98

29-Apr-9829-Jul-98

09-Nov-98

1

10

100

1000

10000

100000

1000000

E C

oli

Co

un

ts (

#/10

0 m

l)

WS 1

WS 2

WS 3

E. Coli Counts 1995 - 1998Lake Champlain Basin Ag Watersheds NMP Project

Statistical summary

Basic descriptive statistics:• Number of observations• Minimum, maximum, range• Mean, median• Variance• Skewness• Distribution

Statistical summary

Always plot your data!

26-May-9408-Sep-94

22-Dec-9406-Apr-95

20-Jul-9502-Nov-95

15-Feb-9630-May-96

12-Sep-9626-Dec-96

10-Apr-97

Time

0

0.2

0.4

0.6

0.8

1

1.2

1.4

Mea

n W

eekl

y To

tal P

Con

cent

ratio

n (m

g/L)

WS 2

WS 3

Statistical summary

Support design of monitoring program:Use observed variance in WQ data to establish effective sampling frequencies

n = t2 s2

d2

where:n = the calculated sample sizet = Student’s t at (n-1) degrees of freedom and

a specified confidence levels = estimate of the population standard deviation

d = acceptable difference of the estimate from the true mean

Spatial Analysis

• Determine general distribution of water quality conditions, impairments

• Identify locations of critical areas, likely pollutant sources

• Determine impacts of a specific source

Temporal Analysis

Seasonality

04-Jan-9512-Apr-95

19-Jul-9530-Oct-95

07-Feb-9615-May-96

19-Aug-9616-Dec-96

31-Mar-9702-Jul-97

06-Oct-9721-Jan-98

29-Apr-9829-Jul-98

09-Nov-98

1

10

100

1000

10000

100000

1000000

E C

oli

Co

un

ts (

#/10

0 m

l) WS 1

WS 2

WS 3

E. Coli Counts 1995 - 1998Lake Champlain Basin Ag Watersheds NMP Project

Temporal Analysis

Trends

0.00

0.10

0.20

0.30

0.40

0.50

0 12 24 36 48 60 72 84 96

Time (months)

Tota

l P C

once

ntra

tion

(mg/

L)

1

10

100

1000

10000

100000

1000000

Time E

. col

i (#/

100

ml)

Temporal Analysis

Flow-concentration relationships

0.01

0.1

1

10

0.01 0.1 1 10

Discharge (L/s)

To

tal

P (

mg

/L)

Temporal Analysis

Relationships among constituents

0

100

200

300

400

500

0 100 200 300 400

Turbidity (NTU)

To

tal S

usp

end

ed S

olid

s (m

g/L

)

.

Identification of causes/sources

• Combine watershed observations + local knowledge + characterization analysis to identify causes and sources of impairment