Colorado River Water Availability Study Colorado Water Workshop Gunnison, Colorado July 21, 2010

1. Colorado River Water Availability StudyColorado Water WorkshopGunnison, ColoradoJuly 21, 2010 CWCB Project Manager Ray Alvarado Consulting Team AECOM AMEC Earth & EnvironmentalCanyon Water ResourcesLeonard Rice Engineers Stratus Consulting

2. “How much water from the Colorado River Basin is available to meet Colorado's water needs?“ Phase IWater Availability under current infrastructure, currently perfected water rights, and current levels of consumptive and non-consumptive water demands Phase IIWater Availability under projected demands from existing, conditional, and new water rights and for additional consumptive and non-consumptive water demands Objectives 2 Colorado River Water Availability Study – Phase I

3. Overall Hydrology Approach Observed Hydrology Paleohydrology Statistical Models 1950 2005 2040 2070 1500 2099 GCM’s & Hydrology StateModStateCU 3 Colorado River Water Availability Study – Phase I

4. Basis for Paleo-Hydrology Douglas-fir, south-central CO 1983 1977 NOAA treeflow.info From NOAA, 4 PRELIMINARY RESULTS – UNDER REVIEW Colorado River Water Availability Study – Phase I

5. Re-sequencing – The Motivation 5 PRELIMINARY RESULTS – UNDER REVIEW Colorado River Water Availability Study – Phase I

6. Paleohydrology – Re-sequencing 1. Repeat 100x 1977 1984 1977 1984 1950 Years 2005 6 Colorado River Water Availability Study – Phase I

7. Overall Hydrology Approach Observed Hydrology Paleohydrology Statistical Models 1950 2005 2040 2070 1500 2099 GCM’s & Hydrology StateModStateCU 7 Colorado River Water Availability Study – Phase I

8. GCMs and Hydrology • Earth • Emissions Scenarios • Global Climate Models • Result: Altered Temperature • and Precipitation • State of Colorado • CDSS Modeling • Result: Water Availability • Colorado River Basin • “Down-Scaled” Projections • Revised Basin-Wide Hydrology • Result: Altered Stream Flows 8 Colorado River Water Availability Study – Phase I

9. GCM Hydrology Process Actual }Climate Effect 1977 1984 Climate Effect Climate Adjusted Actual Climate Adjusted 9 Colorado River Water Availability Study – Phase I

10. Overall Hydrology Approach Observed Hydrology Paleohydrology Statistical Models 1950 2005 2040 2070 1500 2099 GCM’s & Hydrology StateModStateCU 10 Colorado River Water Availability Study – Phase I

11. Natural Flow Results 11 PRELIMINARY RESULTS – UNDER REVIEW Colorado River Water Availability Study | Phase I

12. Natural Flow Results 12 PRELIMINARY RESULTS – UNDER REVIEW Colorado River Water Availability Study | Phase I

13. Natural Flow Results 13 PRELIMINARY RESULTS – UNDER REVIEW Colorado River Water Availability Study | Phase I

14. Natural Flow Results 14 PRELIMINARY RESULTS – UNDER REVIEW Colorado River Water Availability Study | Phase I

15. Natural Flow Results 15 PRELIMINARY RESULTS – UNDER REVIEW Colorado River Water Availability Study | Phase I

16. Natural Flow Results 16 PRELIMINARY RESULTS – UNDER REVIEW Colorado River Water Availability Study | Phase I

17. Natural Flow Results 17 PRELIMINARY RESULTS – UNDER REVIEW Colorado River Water Availability Study | Phase I

18. Natural Flow 18 PRELIMINARY RESULTS – UNDER REVIEW Colorado River Water Availability Study – Phase I

19. Natural Flow Results 19 PRELIMINARY RESULTS – UNDER REVIEW Colorado River Water Availability Study | Phase I

20. Natural Flow Results 20 PRELIMINARY RESULTS – UNDER REVIEW Colorado River Water Availability Study | Phase I

21. Natural Flow Results 21 PRELIMINARY RESULTS – UNDER REVIEW Colorado River Water Availability Study – Phase I

22. Result Summary – Natural Flow • Annual flow increases in some possible futures and decreases in others • Annual flow generally increases in parts of the Yampa River basin and at higher elevation watersheds • Annual flow generally decreases in south-western watersheds and at lower elevations • Shifts toward earlier peak runoff • Flow decreases in late summer and early fall 22 PRELIMINARY RESULTS – UNDER REVIEW Colorado River Water Availability Study – Phase I

23. Uncertainties—Natural Flow • Ranking of uncertainties (Wilby & Harris, 2005), largest to smallest: • GCM Projections • Downscaling method • Hydrology model structure • Hydrology model parameters • Emissions scenarios • Uncertainties interact, but are not additive. 23 PRELIMINARY RESULTS – UNDER REVIEW Colorado River Water Availability Study | Phase I

24. All projections, Glenwood Springs 24 PRELIMINARY RESULTS – UNDER REVIEW Colorado River Water Availability Study | Phase I

25. Ensemble of GCMs, Glenwood Springs 25 PRELIMINARY RESULTS – UNDER REVIEW Colorado River Water Availability Study | Phase I

26. Precipitation Time Series, Lees Ferry 26 PRELIMINARY RESULTS – UNDER REVIEW Colorado River Water Availability Study | Phase I

27. Temperature Time Series, Lees Ferry 27 PRELIMINARY RESULTS – UNDER REVIEW Colorado River Water Availability Study | Phase I

28. Natural Flow Time series at Lees Ferry 28 PRELIMINARY RESULTS – UNDER REVIEW Colorado River Water Availability Study | Phase I

29. Conclusions • Phase I demonstrates broad range of impacts to natural flows. • Complexity of modeling atmospheric circulation • Inherent uncertainties in GCM projections • Robust results • Increased temperatures • Less snowpack and earlier melt 29 PRELIMINARY RESULTS – UNDER REVIEW Colorado River Water Availability Study – Phase I