probabilistic monitoring of streams below small impoundments in tennessee debbie arnwine water...
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Probabilistic Monitoring of Streams Below Small Impoundments in Tennessee
Debbie ArnwineWater Pollution [email protected]
2003 probabilistic study of 75 streams downstream of small impoundments• Macroinvertebrates• Nutrients• Dissolved Oxygen• Temperature• pH• Suspended Solids• Iron and manganese• Habitat• Flow and morphology• Periphyton Density
Over 195,000 small man-made lakes and ponds in Tennessee
1,302 recorded in databases
Potential for public access (safe dams)Built after 1992 (ARAP)
Upstream Reference not Feasible
• Impoundment flooded entire headwaters
• Second impoundment immediately upstream
• Drainage area upstream not 80% within same bioregion.
• Stream size too small upstream of impoundment.
Site reconnaissance(200 recons to get 75 sites)
Other2%
No impound-ment4%
No comparable reference
1%
Insufficient habitat
6%
Intermittent7%
No access11%
No flow32%
Suitable37%
Site Characterization• Impounded 1960 - 1980 (50%)• Surface Discharge (69%)• Forested Drainage Area (77%)• 2nd Order Stream (53%)• < 50 acres (70%)
Macroinvertebrate SamplesSemi-quantitative Single Habitat Spring and Fall
Tennessee Macroinvertebrate Index (TMI)• Taxa Richness• EPT Richness• %EPT• %OC• NCBI• %Dominant• %Clingers• Ky % Nutrient Tolerant
95% Failed to Meet Biocriteria
Failed Spring and Fall
77%
Passed Spring and Fall
5%
Failed Spring only11%
Failed Fall only4%
Uncertain3%
Individual Biometrics
010
2030
405060
708090
100
Per
cent
fai
l
TR
EP
T
%E
PT
%O
C
NC
BI
%D
OM
%C
LIN
G
%N
UT
OL
Biometric
Dominant taxa indicative of nutrients and/or sluggish flow
Fall: Dominant = Cheumatopsyche and Glyptotendipes spp.
Spring: Dominant = Lirceus, Parametriocnemus and Polypedilum spp.
Example of biological data pre and post impoundment
13
3
9
00
2
4
6
8
10
12
14
Nu
mb
er o
f T
axa
EPT Taxa Intolerant Taxa
1997 Pre-impoundment 2003 Post-impoundment
Precipitation generally at or above 25 year averageBristol Airport
0
2
4
6
8
10
12
Month
Inch
es
Avg precip. 1978 - 2002
Precip. 2003 - 2004
Comparison of discharge types
Standpipe Spillway Subsurface Multiple0
10
20
30
40
50
60
70
80
90
100
% M
aint
ain
flow
Geomorphology
49% relative stable channels typical of ecoregion
24% “G-type” –deeply entrenched, unstable banks, heavy sediment loads
20% E-Type in response to lack of flow. Small channel cut within original stream bed.
Original Channel
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
0 5 10 15 20 25 30
Distance (feet)
Ele
vatio
n (fe
et) C
alcu
late
d
Incised Channel
D50 = Bedrock
Dominant bed material becomes smaller below impoundments
Ecoregion Reference Impounded65 Sand Silt66 ,67,68, 69 Boulder/Cobble Gravel71 Bedrock/Cobble Gravel74 Sand Silt
HABITAT70% of sites failed overall habitat
Sedim
ent
Sinuosit
y
Bank Vegetation
Bank Stabilit
y
Pool Varia
bility
Embeddedness
Epifaunal S
ubstrate
Velocity/
Depth
Riparian
Riffle Fr
equency0
102030405060708090
100
Perc
ent F
ailin
g re
gion
al g
uide
lines
Dissolved Oxygen
Fail 5 mg/L21%
Fail trout streams
3%
Fail Blue Ridge
3%Fail NRTS
1%
Pass DO Criteria
72%Based on instantaneous day time measurement
DO Measurements do not tell the whole story.
• Instantaneous measurement during daylight hours.
• Presence of algae at most sites indicates possible large diurnal swings.
• 17% of sites supersaturated.• Percent saturation at 77% of sites below 10th percentile of reference data.
TEMPERATURE11% of sites exceeded criteria.
72% above fall reference temps.
24
68
1012
1416
1820
2224
65
e
66
d
66
e
66
g
67
g
67
h
68
a
68
c
71
f
71
g
71
h
74
a
74
b
TestRefEcoregion
Tem
p (
C)
Suspended Solids
50% of sites had elevated suspended solids.
Land use associated with small impoundments contributes to the problem.
Iron and Manganese61% of sites above recommended iron criterion of 1000 ug/L
93% of sites above reference levels for manganese
Nutrients
NO2+NO3 TP Both05
101520253035404550
FallWinterSpringSummer
% e
xcee
d cr
iteria
41% exceeded NO2+NO3 criteria at least one season.
75% exceeded total phosphorus criteria at least one season.
Detailed Reporthttp://www.tn.gov/environment/wpc/publications/
(or at the back of the room!)
Probabilistic Monitoring of Streams Below Small Impoundments in Tennessee