1. TERMINOLOGY Macrohabitat – water quality and hydrology
Mesohabitat – commonly occurring habitat types
Critical habitat – important to a species even if not common
Microhabitat – depth, velocity and cover within each mesohabitat

2. PHABSIM Study Study Planning Locate reaches and transects
Obtain channel profile and microhabitat data
Develop hydraulic model
Input suitability rating criteria
6. Output suitability available at each flow increment of interest

3. Hypothetical flow control issue
downstream

4. Review physical characteristics
Minor tributary
Flow control
Repeating channel pattern: riffle/run/pool
Major tributary
Unique channel condition: cobble rapids
downstream

5. Link species/lifestages or guilds to specific mesohabitats

6. Define overall study area
Flow control
Juvenile and adult feeding and holding
Spawning bar
downstream

7. Stratify reaches according to physical, hydrologic and habitat use characteristics
Flow control
REACH 1
REACH 2
downstream

8. Select study sites representative of each reach
Representative reach study site
Flow control
REACH 1
REACH 2
Critical reach study site
downstream

9. Representative Study Site
pool
Sand bar
riffle
run

10. Cell Boundaries are located at breaks in habitat types
pool
riffle
run

11. Cell Boundaries (continued)
pool
riffle
run

12. One transect is located within each longitudinal cell
pool
T-4
T-3
riffle
T-1
T-2
run

16. transect T-1 (looking downstream)
headpin
tailpin
Top of bank
Water surface
Toe of bank
Edge of water
Thalweg

17. Verticals are located along each transect to capture key substrate and profile features
headpin
tailpin
Top of bank
Toe of bank
Edge of water
Thalweg

18. Verticals and cell boundaries act to divide each segment into a mosaic of known areas
pool
T-4
T-3
riffle
T-1
T-2

19. Habitat is “pixilated” into a mosaic of known dimensions

20. Calibration flows are gathered across the flow range of interest
High flow (WSL only)
mid flow (WSL and velocities)
low flow (WSL and some velocities)

21. This permits interpolation and extrapolation of other flows
1,800 cfs
100 cfs

23. Model output: Habitat-flow relationships for each river segment

24. Suggested Problem-Solving Process
Review hydrology time series
Compare habitat under existing and alternate flow scenarios
Compare project operation under existing and alternate flow scenarios
Assess extent to which all objectives are met under each flow scenario
Evaluate trade-offs
Re-run alternative scenarios