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Canyon Ferry Water Supply and Projected

Operations

September 2021

December weather resulted in near normal

precipitation and slightly above normal

temperatures in the Gallatin and September Operating Range Basins. Forecast Minimum Median Maximum

Monthly Average Inflow 81.0 91.0 115.0 (kaf) End of Month Elevation (ft) 3779.7 3780.2 3781.2 below Holter Dam 3,000 3,000 3,000 Average River Release (cfs) Watershed above

September 2021 Inflow Forecast

September Volume (kaf) 91 Percent of Average (%) 57

Water Year Historic Inflow (kaf) 2020 133 2019 187 2018 169 2017 148 30 Year Average 159

Canyon Ferry Dam

Western Regional Climate Center CLIMATE SUMMARY National Weather Service August 1-31 Climate September Weather Outlook

Departure from Normal Precipitation August temperatures returned to near Precipitation (inches) average conditions while much needed precipitation fell in the Missouri River Headwaters.

The one-month outlook forecast, dated August 31, is for below normal precipitation and a 33-40 percent chance of above normal temperatures during September.

The basins above Canyon Ferry Reservoir

are designated as extreme to exceptional Temperature Departure from Normal Temperature drought conditions. (F)

MT Drought Monitor Map August 26, 2021

Operations Review

August inflows totaled 99,000 acre-feet, 71 percent of average, while flows below Holter Dam were maintained near 3,000 cfs. The elevation on September 1, 2021 was 3783.25 feet. The below elevation graph shows how 2021 drought is comparable to the drought year of 2000.

Canyon Ferry Dam Inflow & Releases (cfs) Canyon Ferry Dam Elevation (ft)

Operating Outlook

The graphs below depict a range of possible reservoir elevations and river releases over time. The most probable plan is based on current conditions and historical data. The maximum and minimum plans are based upon ranges of possible inflow volumes due to basin variabilities and forecast uncertainties.

Canyon Ferry Reservoir Elevation 3800

3798 Top of Joint-Use - 3797.00Top (1886.9of Active Conservation kaf) - 3797.00 (1908.6 kaf)

3796

3794

3792

3790

3788

3786

3784

3782

Elevation Feet in Elevation 3780

3778

3776

3774

3772

3770 9/1/21 10/1/21 11/1/21 12/1/21 1/1/22 2/1/22 3/1/22 4/1/22 5/1/22 6/1/22 7/1/22 8/1/22 9/1/22

Maximum Probable Most Probable Minimum Probable

Missouri River Flow Below Holter Dam

12000

10000

8000

6000

4000 Flow CFS in Flow

2000

0 Sep-21 Oct-21 Nov-21 Dec-21 Jan-22 Feb-22 Mar-22 Apr-22 May-22 Jun-22 Jul-22 Aug-22

Maximum Probable Most Probable Minimum Probable

Most Probable Inflow Conditions Canyon Ferry Reservoir Initial Elev. 3783.25 ft 2021 Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Total ------Reservoir Inflow kaf 91.0 125.0 155.0 155.0 150.0 165.0 230.0 260.0 420.0 540.0 200.0 110.0 2601.0 HV Canal Diversions kaf 11.0 0.0 0.0 0.0 0.0 0.0 0.0 8.0 16.0 17.9 18.0 18.0 88.9 HV Pump Turbines kaf 14.9 0.0 0.0 0.0 0.0 0.0 0.0 11.3 20.2 19.2 18.2 19.3 103.1 Turbine Release cfs 2623 2877 2835 2853 2828 2793 2781 2820 2804 3551 3739 3672 Spill kaf 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Generation gwh 17.856 20.386 19.224 19.939 19.642 17.405 19.344 19.368 20.460 27.576 30.802 29.686 261.688 River Release cfs 2874 2877 2835 2853 2828 2793 2781 3010 3132 3874 4035 3986 End-Month Content kaf 1351.0 1299.1 1285.4 1265.0 1241.1 1251.0 1310.0 1382.9 1594.3 1885.9 1819.8 1666.7 End-Month Elevation ft 3780.2 3778.3 3777.8 3777.0 3776.1 3776.5 3778.7 3781.3 3788.2 3797.0 3795.1 3790.5 Holter Dam Release cfs 3000 3001 3000 3001 3001 3000 3001 3200 3274 4101 4100 4100

Minimum Probable Inflow Conditions 2021 Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Total ------Reservoir Inflow kaf 81.0 110.0 140.0 140.0 135.0 140.0 195.0 233.0 295.0 350.0 140.0 91.0 2050.0 HV Canal Diversions kaf 11.0 0.0 0.0 0.0 0.0 0.0 0.0 7.0 16.0 17.9 18.0 18.0 87.9 HV Pump Turbines kaf 15.0 0.0 0.0 0.0 0.0 0.0 0.0 11.6 24.5 24.4 23.5 25.1 124.1 Turbine Release cfs 2677 2911 2897 2926 2934 2872 2830 2655 2576 2427 2511 2527 Spill kaf 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Generation gwh 18.288 20.609 19.584 20.237 20.088 17.539 19.046 17.208 17.484 16.128 17.633 17.484 221.328 River Release cfs 2929 2911 2897 2926 2934 2872 2830 2850 2975 2837 2893 2936 End-Month Content kaf 1337.7 1268.7 1236.3 1196.4 1151.0 1131.5 1152.5 1208.9 1305.0 1468.3 1412.4 1304.9 End-Month Elevation ft 3779.7 3777.2 3776.0 3774.4 3772.6 3771.8 3772.7 3774.9 3778.5 3784.1 3782.3 3778.5 Holter Dam Release cfs 3001 3000 3001 3000 3001 3001 3000 3001 3000 3001 3000 3001

Maximum Probable Inflow Conditions 2021 Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Total ------Reservoir Inflow kaf 115.0 180.0 210.0 230.0 195.0 195.0 270.0 380.0 680.0 850.0 350.0 170.0 3825.0 HV Canal Diversions kaf 12.0 0.0 0.0 0.0 0.0 0.0 0.0 11.0 18.4 17.0 18.4 18.4 95.2 HV Pump Turbines kaf 16.0 0.0 0.0 0.0 0.0 0.0 0.0 14.6 23.0 18.3 18.3 19.2 109.4 Turbine Release cfs 2469 2729 2810 3015 3915 3833 4425 5090 5002 4690 4537 4614 Spill kaf 0.0 0.0 0.0 0.0 0.0 0.0 0.0 51.5 167.0 227.6 42.3 18.1 506.5 Generation gwh 16.632 19.418 19.584 22.246 30.058 26.342 33.629 36.504 37.944 36.720 37.944 37.944 354.965 River Release cfs 2738 2729 2810 3015 3915 3833 4425 6201 8093 8823 5523 5221 End-Month Content kaf 1382.1 1394.3 1437.1 1481.7 1436.0 1418.1 1416.0 1416.0 1580.0 1888.0 1880.0 1710.6 End-Month Elevation ft 3781.2 3781.7 3783.1 3784.6 3783.1 3782.5 3782.4 3782.4 3787.7 3797.0 3796.8 3791.8 Holter Dam Release cfs 3000 3001 3000 3201 4100 4100 4700 6452 8481 9640 5892 5513 Contact Us Stephanie Micek Clayton Jordan Chris Gomer [email protected] [email protected] [email protected] 406-247-7320 406-247-7332 406-247-7307 http://www.usbr.gov/gp/lakes_reservoir/wareprts/main_menu.html https://www.usbr.gov/gp/hydromet/