1. HYDROSPHERE Resource Consultants
Severe and Sustained Drought
July 30, 2004
29th Colorado Water Workshop

2. The Project The beginnings Objectives Hydrology Impacts Responses
Harold Fritts, Laboratory for Tree Ring Research, U of Arizona—
Noted that there had been more extreme and extended droughts in the tree ring record than have been observed in recent records.
Gilbert White, University of Colorado
Urged study of the impacts of extraordinary drought
First phase report by Frank Gregg, David Getches.
Structure
Hydrology
Institutions
Engineering
Impacts
Gaming
Objectives
Responses

3. What is a drought? Hydrologic drought System drought
Consecutive flows below the mean flow
Depends on mean
Mean depends on period of record
System drought
Low-flow conditions that cause distress
Depends on storage, deliveries, policy

4. The Drought System context is c. 1992 38-year scenario (1579-1616)
Re-arranged to increase onset intensity
Low flow period, recovery period
–year return interval
“Probable extreme drought”

5. SSD Drought Trace

6. Impacts Reservoir storage Water availability Power and energy
Water quality
Social
Economic
Environmental

7. Reservoir Contents

8. Water Availability

9. Energy

10. Water Quality

11. Mitigation Actions identified in gaming Intrastate actions
Interstate actions
Reverse equalization
Relaxation of compact

12. Lee Ferry Deliveries

13. Powell

14. Mead

15. Depletions

16. You are here

17. Powell: SSD vs. Current

18. Lee Ferry: SSD vs. Current

19. Mead: SSD vs. Current

20. The Wisdom of Chairman Yogi
It’s like déjà vu all over again.
It ain’t over till it’s over.
Making predictions is hard, particularly about the future.
The future ain’t what it used to be.
It appears that we’re in situation similar to the SSD drought
Webb USGS analysis
Don’t know the nature of a drought until it’s over
Betting man—it won’t develop
But, rules of the game may have changed.
What happened--Possibilities
SSD analysis is optimistic
Physical models understate losses
Lower basin policies have delivered more water to CA
We envisioned this drought in the distant future, and assumed all parties would be within contractual/compact limits
SOI is using different surplus/shortage criteria for Mead
State’s allocation—variable, depends on last 10+ years of hydrology
If there is a compact call, quantification of PPRs will be important
Preserving PPRs is important

22. Upper Colorado River Compact Issues
Quantification of states’ depletions
Quantification of PPRs
Quantification and allocation of channel losses
Quantification and allocation of reservoir evaporation
Overdrafts

23. Intrastate Issues Quantification of entitlement Quantification of PPRs
Avoidance of overdrafts
Administration of curtailment
Mechanisms for Subordination/Offsets

24. Modeling Issues Colorado River Compact Upper Colorado River Compact
Mexico Treaty
Intrastate rights
Present Perfected Rights
Physical models
Probabilistic Forecasting