Upper Missouri River Basin Water Year 2018 Summary of Actual Operations U.S. Department of the Interior Bureau of Reclamation Great Plains Region Table of Contents Annual Operating Plans for Water Year 2018 for Units Under the Responsibility of the Montana Area Office .................................................................................................................... 8 Hydrologic Conditions and Flood Control ................................................................................. 8 October through December ......................................................................................................... 8 January through March ............................................................................................................. 15 April through June .................................................................................................................... 19 July through September ............................................................................................................ 29 Flood Benefits .............................................................................................................................. 32 Unit Operational Summaries for Water Year 2018 ................................................................. 35 Clark Canyon Reservoir ............................................................................................................ 35 Important Events – Water Year 2018 ................................................................................... 38 Canyon Ferry Lake and Powerplant ......................................................................................... 42 Important Events- Water Year 2018 ..................................................................................... 45 Helena Valley Reservoir ........................................................................................................... 50 Sun River Project ...................................................................................................................... 52 Gibson Reservoir .................................................................................................................. 52 Pishkun Reservoir ................................................................................................................. 55 Willow Creek Reservoir ....................................................................................................... 56 Important Events – Water Year 2018 ................................................................................... 59 Lake Elwell (Tiber Dam) .......................................................................................................... 66 Important Events – Water Year 2018 ................................................................................... 69 Milk River Project ..................................................................................................................... 74 Lake Sherburne ..................................................................................................................... 74 Fresno Reservoir ................................................................................................................... 77 Nelson Reservoir ................................................................................................................... 80 Important Events – Water Year 2018 ................................................................................... 81 Bighorn Lake and Yellowtail Powerplant ................................................................................. 89 Important Events - Water Year 2018 .................................................................................... 93 Annual Operating Plans for Water Year 2018 for Units Under the Responsibility of the Wyoming Area Office ................................................................................................................. 99 Wind River and Shoshone River Basin Climate Summaries .................................................. 99 Fall: October through November .............................................................................................. 99 Winter: December through February ........................................................................................ 99 1 Spring/Summer: March through September (NWS) ............................................................... 100 Unit Operational Summaries for Water Year 2018 ............................................................... 104 Riverton Unit .......................................................................................................................... 104 Bull Lake Reservoir ............................................................................................................ 104 Pilot Butte Reservoir ........................................................................................................... 106 Boysen Reservoir and Powerplant ...................................................................................... 111 Anchor Reservoir .................................................................................................................... 117 Shoshone Project and Buffalo Bill Unit.................................................................................. 120 Heart Mountain Powerplant ................................................................................................ 120 Shoshone Powerplant .......................................................................................................... 120 Buffalo Bill Powerplant ...................................................................................................... 120 Spirit Mountain Powerplant ................................................................................................ 121 Buffalo Bill Dam and Reservoir ......................................................................................... 121 Important Events - 2018...................................................................................................... 123 Summary of Reservoir Operations for Benefit of Fish and Wildlife, Environment, and Recreation .................................................................................................................................. 126 Bull Lake Reservoir ................................................................................................................ 126 Boysen Reservoir .................................................................................................................... 126 Buffalo Bill Reservoir ............................................................................................................. 126 Projected Operating Plans for Bighorn Basin WY 2019 ....................................................... 128 Bull Lake Reservoir ................................................................................................................ 128 2019 Operating Plans .............................................................................................................. 128 Boysen Reservoir and Powerplant .......................................................................................... 134 Irrigation Season Release .................................................................................................... 134 Non-irrigation Season Release ............................................................................................ 134 General Operating Procedures ............................................................................................ 134 2019 Operating Plans .......................................................................................................... 135 Buffalo Bill Reservoir and Powerplants ................................................................................. 138 Normal Operating Procedures ............................................................................................. 138 2019 Operating Plans .......................................................................................................... 138 Annual Operating Plans for Water Year 2018 for Units Under the Responsibility of the Dakota Area Office ................................................................................................................... 144 Weather Summary for North and South Dakota Water Year (WY) 2018 .......................... 144 Flood Benefits ............................................................................................................................ 147 Reservoirs in North and South Dakota and Northeastern Wyoming ...................................... 147 2 Unit Operational Summaries for WY 2018 ............................................................................ 149 Dickinson Reservoir................................................................................................................ 149 Background ......................................................................................................................... 149 WY 2018 Operations Summary .......................................................................................... 149 Monthly Statistics for WY 2018 ......................................................................................... 150 Heart Butte Reservoir ............................................................................................................. 153 Background ........................................................................................................................