1. Yellowtail Dam & Bighorn Lake Water Supply & Operations Meeting Billings, Montana October 8, 2009 RECLAMATION Managing Water in the West

2. Welcome & Introductions

3. Purpose of Meeting  Public outreach / education regarding Yellowtail Dam & Bighorn Lake  Recap operations during water year 2009  Present operation scenarios for fall / winter 2009-2010  Obtain feedback / comment from public & interested parties

4. Montana Area Office is responsible for managing the water supplies and administering Reclamation programs for Reclamation projects located in Montana east of the continental divide.

5. The Montana Area Office monitors hydrologic and climatic conditions, prepares inflow projections and operation plans, and directs water releases from Yellowtail Dam.

6. YELLOWTAIL DAM, BIGHORN LAKE AND AFTERBAY

7. YELLOWTAIL DAM and BIGHORN LAKE Visitor Center Powerplant Bighorn Lake Spillway Inlet

8. YELLOWTAIL DAM, BIGHORN LAKE and AFTERBAY Visitor Center Yellowtail Dam Substation Yellowtail Afterbay Dam

9. YELLOWTAIL AFTERBAY DAM and AFTERBAY Bighorn Canal Radial Gates Sluice Gates Afterbay Dam Afterbay Sewage Lagoons

11. OPERATIONS - A BALANCING ACT AMONG THE COMPETING INTERESTS

13. Mountain Snowpack Precipitation Inflow to Bighorn Lake Bighorn River Releases Bighorn Lake Storage Conditions Recap of Water Year 2009

16. Peaked on 4/16 @ 106% of average

17. Recap of Water Year 2009

18. Bighorn Lake Annual Inflow Distribution Based on 1967-2009 Data

19. Recap of Water Year 2009 2009 – 2,730 kaf Ave. – 2,357 kaf

20. Recap of Water Year 2009 2009 – 1,657 kaf Ave. – 1,113 kaf

21. Recap of Water Year 2009 WY-2009 April-July Inflow – 1,657 kaf (149% of average) WY-2009 Annual Inflow – 2,730 kaf (116% of average)

22. Recap of Water Year 2009

23. Peaked on 7/06 at 3647.92 feet 7.92 feet above full pool 5.42 feet higher than in 2008

24. Summary Recapping Water Year 2009 Water year started out with good precipitation – Oct. above average but dropped to below average during Nov. Precipitation returned to above average during Dec. & Jan. Precipitation dropped to well below average in Feb. returned to well above average during March & April. Unlike last year, precipitation was well below average in May but returned to well above average in June through Aug. with Sept. dropping well below normal. October-March inflows were 80% of average totaling 732 kaf. April-July inflows were 149% of average totaling 1,657 kaf. Annual inflows were 116% of average totaling 2,730 kaf. Bighorn Lake reached a low level at elevation 3619.50 on May 20. Bighorn Lake reached a peak level at elevation 3647.92 on July 6. Bighorn Lake rose 28.4 feet from May 20 to July 6. Fall & winter releases were maintained at 2,450 cfs. Beginning in early April, releases were gradually increased from 2,450 cfs to nearly 4,440 cfs by late May. Beginning in late June & into early July, releases were gradually increased to a peak of 12,500 cfs to control the spring runoff and rate of fill. Rains in June accompanied by unusually large releases out of Buffalo Bill & Boysen, caused inflows to reach a peak of 16,760 cfs on June 22. Since July 6, storage has slowly declined to elevation 3640 by September 22 and has essentially remained near full. Current lake level is only about 0.5 foot below full, 2 nd highest of record and releases are currently being maintained at 2,800 cfs.

25. BIGHORN LAKE CURRENT CONDITIONS Elevation 3639.48 ft – 0.52 feet below full pool 0.13 feet lower than last year Storage 1,063,500 af – 99% full Inflows = 3,450 cfs Total Outflow = 2,800 cfs River = 2,800 cfs BIA Canal = 0 cfs October 7, 2009

26. Inflow Forecast to Bighorn Lake – WY-2010 WY-2009 Oct-Mar Actual Inflow – 732 kaf WY-2010 Oct-Mar Inflow Forecast – 778 kaf

27. OPERATION SCENARIOS

28. Bighorn Lake Operation Scenarios Most Probable Inflow Scenario: October – March Inflow forecast at 778 kaf Maintain fall and winter release at 2,720 cfs through March Reservoir level expected to reach elevation 3620.6 by the end of March. Generation during October – March would total 382.6 GWHrs.

29. Most Probable Inflow Scenario

31. Bighorn Lake Operation Scenarios Minimum Probable Inflow Scenario: October – March Inflow forecast at 685 kaf Maintain fall and winter release at 2,700 cfs through January and gradually reduce to 2,300 cfs in February and to 2,000 cfs in March Reservoir level expected to reach elevation 3618.4 by the end of March. Generation during October – March would total 349.9 GWHrs.

32. Minimum Probable Inflow Scenario

34. Bighorn Lake Operation Scenarios Maximum Probable Inflow Scenario: October – March Inflow forecast at 843 kaf Maintain fall and winter release at 2,770 cfs through February and increase release to 3,535 cfs during March Reservoir level expected to reach elevation 3620.8 by the end of March Generation during October – March would total 408.9 GWHrs.

35. Maximum Probable Inflow Scenario

37. Three Probable Runoff Scenarios

39. Discussion & Comments

40. The information presented at this meeting can be found on the Montana Area Office website at: www.usbr.gov/gp/mtao/yellowtail/index.cfm. www.usbr.gov/gp/mtao/yellowtail/index.cfm Please mail comments to: Ms. Paula A. Holwegner Bureau of Reclamation 2900 4 th Avenue North, Suite 501 Billings, MT 59107 fax your comments to: 406-247-7338 or email your comments to: pholwegner@gp.usbr.govpholwegner@gp.usbr.gov by October 13, 2009 Comments ?

41. Reclamation’s Internet Website http://www.usbr.gov/gp/water/ near real-time data available through the HYDROMET data system summaries and plots of historical data annual reservoir operating plan publication monthly water supply reports project data snow plots links to related internet sites

42. Bighorn Lake April-July Inflow Forecasted vs Actual