Characterizing Baseline Water Body Conditions
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