1. Commonwealth of Virginia Flow-Ecology
Project Meeting
VDEQ
June 23, 2011

2. Grouping Biological Data Hydrologic Modeling Point

3. Hydrologic Modeling Outputs
Which gauges used, what stream orders
What verifications done
Natural sites – one hydrograph
Altered sites – two hydrographs
actual (altered)
‘naturalized’
Calculate IHA parameters and % change (who)

4. Example Rules – defining the sample unit (‘pour points’)
Groupings
Use stream flow classes (6)
Consider size separation within classes, e.g.:
Strahler order 1-3
Order 4-6
Elevation/gradient may also be important

5. Example Stream Network1 1
Dots: bio sample sites
Numbers: Strahler order
X: USGS gauge 2 2 2 3 3 4
Discharge X X

6. Defining the sample unit (‘pour points’)
Minimize extrapolation of hydrologic model beyond its calibration (USGS gauges)
Few USGS gauges on streams <2nd or 3rd order
Distribution of biological data
From NHD+ (1:100,000 scale), samples on 1st to 3rd order

7. Example Stream Network1 1
Dots: bio sample sites
Numbers: Strahler order
X: USGS gauge 2 2 2 3 3 4
Discharge X X

8. Gauged data– defining the sample unit (‘pour points’)
Relation of gauges and biological stations random
Several to none in gauged watershed
Gauge on segment of same stream order as biological sites (? – hydrologic opinion?)
Tribs can come in if order remains unchanged (?)
Decision on discharges entering above biological stations
Decision on maximum distance between gages and biology

9. Example Stream Network1 1
Dots: bio sample sites
Numbers: Strahler order
X: USGS gauge 2 2 2 3 3 4
Discharge X X

10. Modeled data– defining the sample unit (‘pour points’)
Some pour points may represent several biological points
30-50 data pairs per class