Biological_-_Environmental_Classification_(BEC)_system

BIOLOGICAL - ENVIRONMENTAL
CLASSIFICATION (BEC) SYSTEM AND
SUPPORTING FLOW – BIOLOGY
RELATIONSHIPS IN NORTH CAROLINA –
PROJECT UPDATE
Conducted by: RTI and USGS
Funded by: Environmental Defense
Fund, NC DENR, and NC WRC
LAST MEETING……
BEC stream classification
system:
• Do multifactor response
models offer better
predictions of biological
response?
•Do a priori regional
classifications improve
strength of flow-biology
relationships?
RTI IR&D flow-biology
relationships:
• Riffle-run fish guild
(normalized by basin)
• Wadeable streams in
NC
Annual Ecodeficit (%)
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BEC STREAM CLASSIFICATION
• Multifactor response models?
– NC fish (species richness of riffle-run guild)
– Flow metrics:
• Summer Ecodeficit
• decreases in Annual 30-day Minimum Flow
– Best model fit:
• Flow metric
• Ecological Drainage Unit (EDU) regions
• Slope
• % Forest Cover (correlated with flow metric)
• Average Temperature
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NOTE: Results are similar for invertebrates
BEC STREAM CLASSIFICATION
•A priori regional classification improve strength of flow-
biology relationship?
– NC fish (species richness of riffle-run guild; RTI flow-
biology methodology – normalized by basin; response of
90th percentile data)
– Flow-biology relationships by EDU
– Results:
• Flow-biology relationships were not consistently strengthened
by splitting up by EDU
– only 4 of 10 EDUs had significant flow-biology relationships
– only 1 EDU had a better model fit than the state-wide model
(Albemarle Pamlico Piedmont EDU)
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RECOMMENDATION
• Use state-wide flow-biology relationships for fish and benthos
(based on RTI flow-biology methodology) to support
determination of ecological flows
– Biological response:
•Fish
– Species richness of Riffle-run guild
– Normalized by basin
• Benthos
– EPT Richness
– Normalized by Omernik Level III
– Flow metric:
• Ecodeficit
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ECODEFICIT
• Ecodeficit is a measure of the reduction in volumetric water availability
• 20% ecodeficit = 20% reduction in volumetric water availability (over a
defined period of time)
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Probability of Exceedance (%)
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NHD+ Catchments in Roanoke Basin
ANNUAL ECODEFICIT - FISH
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ANNUAL ECODEFICIT - BENTHOS
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Note: 50% reduction
in biological condition
is beyond the range
of the data
ANNUAL ECODEFICIT - COMBINED
9
Benthic EPT Richness
Fish Species Richness
ANNUAL ECODEFICIT - COMBINED
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• Annual versus seasonal ecodeficit – biological responses
relationships and associated “biological condition” thresholds
Metric 10% 20% 30% 10% 20% 30%
Annual EcoDeficit 7 1116121826
Winter Deficit 7 1116111624
Spring Deficit 7 1115111725
Summer Deficit 9 1318132031
Fall Deficit 10 15 20 14 21 30
Average 8 12 17 12 18 27
Standard Deviation 122123
Fish: Species Richness Benthos: EPTR
WHAT’S NEXT?
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• Depending on the current condition of a stream, how
much degradation in the biological condition is EF-
SAB (NCDENR) willing to tolerate?