INTRODUCTION Annual reports on actual operations and operating plans for reservoir regulation activities were initiated in 1953. The Montana Area Office (MTAO), Wyoming Area Office (WYAO), Dakotas Area Office (DKAO) and the Regional Office are all responsible for preparing reports on actual operations and operating plans for reservoirs within the Upper Missouri River Basin above Sioux City, Iowa. This report briefly summarizes weather and streamflow conditions in the Upper Missouri River Basin during water year 2009, which are principal factors governing the pattern of reservoir operations. This report also describes operations during water year 2009 for reservoirs constructed by the Bureau of Reclamation (Reclamation) for providing flood control and water supplies for power generation, irrigation, municipal and industrial uses, and to enhance recreation, fish, and wildlife benefits. This report includes operating plans to show estimated ranges of operation for water year 2010, with a graphical presentation on a monthly basis. The operating plans for the reservoirs are presented only to show possible operations under a wide range of inflows, most of which cannot be reliably forecasted at the time operating plans are prepared; therefore, plans are at best only probabilities. The plans are updated monthly as the season progresses as more reliable estimates of inflow become available. A report section devoted to Energy Generation is included at the end of this report. The energy generation and water used for power at Reclamation and Corps of Engineers (Corps) plants are discussed, and the energy generated in 2009 is compared graphically with that of previous years. Energy produced at the Reclamation and Corps mainstem plants is marketed by the Department of Energy. Table CET6, entitled "Total Reservoir Storage Contents at the End of Water Years 2008 and 2009," compares the water storage available at the beginning of water year 2010 to that available at the beginning of water year 2009. Table CET7 is a summary of the end of month storage contents for each reservoir during water year 2009. The MTAO also assists in the preparation of plans for operation of the Corps reservoir on the mainstem of the Missouri River by furnishing depletion estimates based upon the operating plans presented in this report. All references to a year in this report will mean the water year extending from October 1 through September 30, unless specifically stated otherwise. 1 SUMMARY OF HYDROLOGIC CONDITIONS AND FLOOD CONTROL OPERATIONS DURING 2009 Antecedent Conditions: The conditions that existed following the 2008 water year indicated that the drought conditions remained prominent in southeast Montana. Temperatures finished the year below average, while the average annual precipitation varied widely, providing mixed feelings for the upcoming year. Conditions for the Upper Missouri River Basin showed moderate improvement overall. The mountain and valley precipitation for most basins in Montana east of the Continental Divide and the Bighorn River Basin in Wyoming were near to above normal during early fall through March except for the Sun River, Marias River, Milk River and St. Mary River Basins in northwest Montana where valley precipitation was below average. During May the precipitation reached levels much above average in the mountains and valleys, before dropping off to low levels to finish out the end of the year in all the basins except the Milk River and St. Mary River Basins which received good precipitation in June as well. Near normal temperatures and precipitation throughout September in most of the basins brought a glimmer of light to the situation as most basins finished out the year with precipitation levels between 80 and 123 percent of normal. The exception was the Beaverhead River Basin where valley precipitation was only 67 percent of average for water year 2008. According to the Natural Resources Conservation Service (NRCS), the snowpack on April 1, 2008, was near to above normal in all the river basins in Montana and Wyoming. It ranged from 96 percent of normal in the Wind River Basin above Boysen Reservoir in Wyoming to 109 percent of normal in the Milk River and St. Mary River Basins. Precipitation improved during April from that experienced in March in all of the basins in Montana, but was significantly less in Wyoming above the Bighorn River Basin. Water year 2008 ended with varying storage levels. Clark Canyon Reservoir was only 52 percent of average while Sherburne Reservoir was 421 percent of average. The Reclamation reservoirs with the least amount of carryover storage were Clark Canyon and Gibson Reservoirs at 37 and 23 percent of full capacity. October through December: Precipitation for the 2009 water year began with precipitation totals varying considerably. Mountain precipitation during October ranged between 53 percent of average in the Marias River Basin to 117 percent of normal in the Beaverhead River Basin, while the valley precipitation varied from only 16 percent of average in the Marias River Basin to 158 percent of average in the Bighorn River Basin. The valley and mountain precipitation in November ranged from 37 and 50 percent of average respectively, in the St. Mary River Basin to 106 and 128 percent of average in the Gallatin River Basin. During December weather conditions improved as frequent storms brought moderate precipitation to many areas of the mountains and valley regions in Montana and Wyoming. The valley precipitation values in December ranged from 118 percent of average in the Gallatin River Basin to 266 percent in the Marias River Basin. 2 The mountain precipitation ranged from 144 percent above Lima Reservoir in the Beaverhead River Basin to 76 percent of average above Lake Sherburne in Glacier National Park. For some basins, the early precipitation patterns indicated drought conditions may continue. However, by December hydrologic and climatic conditions showed signs of improvement around the state with the exception of the St. Mary River Basin, Tables MTT1A and MTT1B. January through March: The mountain precipitation during January varied from 54 percent of average in the Beaverhead River Basin to 140 percent of average in the Bighorn River Basin. The valley precipitation varied from only 26 percent of average in the Gallatin River Basin to 128 percent of average in the Milk River Basin. On January 1, the NRCS reported mountain snowpack in Montana east of the Continental Divide ranging from 58 percent of normal in the St. Mary River Basin to 109 percent of normal in the Jefferson River Basin, Table MTT2. The mountain snowpack was 89 percent of normal in the Bighorn River Basin in Wyoming. Mountain snow water content statewide was 97 percent of average and 120 percent of last year. Precipitation during February was light. The mountain precipitation varied from 47 percent of average in the Beaverhead River Basin to 86 percent of average above Lake Sherburne. The valley precipitation was slightly better and varied from only 27 percent of average in the Beaverhead River Basin to 126 percent of average in the Marias River Basin. By March 1, about 80 percent of the seasonal snowpack should be on the ground. On March 1, the NRCS reported snowpack conditions statewide was about 87 percent of average and about 81 percent of last year at this time. Precipitation was much improved during March. During March, the mountain precipitation varied from 110 percent of average in the Bighorn River Basin to 143 percent of average in the Beaverhead River Basin above Clark Canyon Reservoir. The valley precipitation varied from only 28 percent of average in the Milk River Basin to 231 percent of average in the Jefferson River Basin. On April 1, the NRCS reported snowpack conditions statewide was about 100 percent of average and about 91 percent of last year at this time. April through June: On April 1, the mountain precipitation varied from 77 percent of average above Sherburne Reservoir to 146 percent of average in the Sun River Basin. The valley precipitation varied from 130 percent of average in the Bighorn River Basin to 227 percent of average in the Gallatin River Basin. The April and May temperatures were near to below average across much of Montana and Wyoming. Numerous spring storms also frequented much of the state. These cooler temperatures delayed the high elevation snowmelt and above normal precipitation resulted in a later snowmelt runoff season and also produced higher snowpack peaks later than normal. According to NRCS records, the May 1 mountain snow water contents statewide for Montana were 102 percent of average and 76 percent of last year. 3 4 5 6 7 8 The precipitation across Montana during May declined significantly from the previous month. The mountain precipitation varied from only 39 percent of average in the Sun River Basin to 77 percent of average in the Gallatin River Basin. The valley precipitation ranged from 29 percent in the St. Mary River Basin to 72 percent of average in the Gallatin River Basin. In general, all basins above Reclamation projects in Montana received precipitation rates much below average during May. However; due to temperatures staying cool, the high elevation snowmelt was substantially delayed and had just started to melt. According to NRCS records, the June 1 mountain snow water contents statewide for Montana were 92 percent of average and 62 percent of last year. The above figures come from NOAA and show how April ranked in terms of 115 years of record from Coldest, and Driest to Warmest and Wettest. In 2009 Temperature ranked at 44 and precipitation was at 96. The colors may help bring things to life better as the actual numbers are hard to read at this size. Normally the higher elevation snowpack reaches peak accumulations around the middle of April and begins to melt out. However, because of the cooler temperatures experienced in April and May and the frequent spring storms in May, much of the higher elevation snowmelt did not begin to occur until late May or early June.