1. Liberty Lake Watershed Analysis
Brian E. Drake
The University of Texas at Austin
April 24, 2007
CE394K.2 - Hydrology

2. Outline Geologic Formation and Background Vegetative Zone of Influence
HEC-HMS

3. Geologic Formation Creek dammed by ice sheet
Lake Missoula flood deposits

4. Lake Missoula Present roughly 12,000 years ago
Covered much of western Montana
Volume = 530 mi3
Ice Dam = 2500 ft

6. The Floods Likely multiple floods Peak flow = 386 x 106 cfs
Velocity = mph

7. Liberty Lake Deposits

8. Lake and Watershed Characteristics
Lake = 708 acres
Watershed = 14 mi2
15 miles east of Spokane, WA

9. Outline Geologic Formation and Background Vegetative Zone of Influence
HEC-HMS

10. Motivation Coupling hydrological/biological processes
Example: Transpiration causing diel streamflow fluctuations
Improve process interactions and water balance accuracy
(Bond et al. 2002)

11. Data Collection
Stilling well
Hourly depth records
Calibrated to flow

12. Vegetative Water Use

13. Width of Influence, W (ft)
Zone of Influence
Transpiration Rates
2.4 – 330 ft3/acre/hr
Used 120 ft3/acre/hr for computations
Month
Width of Influence, W (ft)
May 12
June 29
July 24 W

14. Outline Geologic Formation and Background Vegetative Zone of Influence
HEC-HMS

15. Goals Gain exposure to HEC-HMS
Define storm capable of causing lake property damage
Adjudicated lake elevation =
Flooding at 2054’

16. Results to Date 2 yr – 6 hr Storm Peak Flow = 24.4 cfs
Volume = 4.9 acre-ft
100 yr – 24 hr Storm
Peak Flow = 6376 cfs
Volume = 871 acre-ft

17. Conclusions Past changes may give insight to future
Diel streamflow fluctuations can be used to quantify vegetative zone of influence
Very dependent on transpiration rates
MODIS Leaf Area Index (LAI)
HEC-HMS is a powerful tool for rainfall-runoff modeling
Still need to determine storage-elevation relationship

18. Questions?