2003 Actual Operations

INTRODUCTION Annual reports on actual operations and operating plans for reservoir regulation activities were initiated in 1953. The Montana Are Office, Wyoming Area Office, Dakota Area Office and the Regional Office are all responsible for preparing reports on actual operations and operating plans for reservoir within the Upper Missouri River Basin above Sioux City, Iowa. This report briefly summarizes weather and strearnflow conditions in the Upper Missouri river Basin during water year 2003, which are principal factors governing the pattern of reservoir operations. This report also describes operations during water year 2003 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 2004, 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, to better coordinate the actual water and power requirements with more reliable estimates of inflow. A report 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 discusses, and the energy generated in 2003 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 2000 and 2003," compares the water storage available at the beginning of water year 2004 to that available at the beginning of water year 2003. Table CET7 is a summary of the end of month storage contents for each reservoir during water year 2003. The Montana Area Office also assists in the preparation of plans for operation of the Corps reservoir on the main stem 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 I through September 30, unless specifically stated otherwise. 1 SUMMARY OF HYDROLOGIC CONDITIONS AND FLOOD CONTROL DURING 2003 Antecedent Conditions: There were extremely dry conditions that existed following the 2002 water year. The temperatures and precipitation for water year 2002 varied significantly between basins. Temperatures were warm in the fall and ranged from cooler to warmer than average for the spring and summer. Precipitation for many basins was much below normal with the only exceptions being areas in northcentral and central Montana. The Marias, Milk and St. Mary basins all finished the water year with above normal mountain and valley precipitation. The Sun River basin finished the year with near average mountain and valley precipitation. The 2002 snowpack as of April 1 ranged from below to above normal in the river basins in Montana and Wyoming. It ranged from 73 percent of normal in the Bighorn River basin to 118 percent of normal in the St. Mary River basin. The low snowpack, in addition to the below average valley rains produced dry conditions east of the Continental Divide, excluding the north and northcentral parts of Montana. The dry conditions were reflected in the inflows for the year. Inflows for water year 2002 were much below average and several low inflow records were set. The exceptions were Lake Sherburne, Lake Elwell and Fresno Reservoir which received above average annual inflow. Annual inflow was the fourth lowest on record for Canyon Ferry, the second lowest for Clark Canyon Reservoir, and the lowest on record for Bighorn Lake. The end of September storage for Reclamation reservoirs ranged from much below average to above average for the month of September. Releases during 2002 were very conservative at Reclamation projects. At three major Reclamation projects, Yellowtail, Clark Canyon, and Canyon Ferry Dams releases were below the minimum desired for the fishery as recommended by the Montana Fish, Wildlife, and Parks (MFWP). October through December: The 2003 snowfall season got off to a very slow start. Even slower than last year at this time. The mountain snowpack distribution during 2003 was generally like year 2002, where low and mid elevation mountain snowpack was generally worse than the high elevation mountain snowpack. Persistent north winds resulted in cooler and drier conditions for much of October. The El Nino forecast for above average temperatures and below average precipitation held true for much of the early part of water year 2003, with the exception of October temperatures. For most Montana reporting stations located east of the Continental Divide, precipitation during October through December ranged from below normal to much below normal. This was an indication of what was to come. For the northern Rockies, the drought 2 kept its grip for the fourth consecutive year. Precipitation for the Bighorn Basin in Wyoming was also much below normal, Table MTT3. October through December inflows were much below normal at all Reclamation reservoirs in Montana east of the Continental divide with the exception of Fresno Reservoir. During the fall several new record low inflows were set. A new record low inflow was recorded at Canyon Ferry for November, while Clark Canyon had a new record low for December. A new record low inflow was recorded for Bighorn Lake during both November and December. January through March: On January 1, the Natural Resources Conservation Service reported mountain snowpack in Montana east of the Continental Divide where Reclamation facilities are located ranged from 9 percent of normal in the Milk River Basin to 68 percent of normal in the Beaverhead River Basin. The mountain snowpack was 72-74 percent of normal in the Bighorn River Basin of Wyoming. Mountain snow water content statewide was 63 percent of average and 77 percent of last year and was generally 20 to 30 percent below 2002. West of the Continental Divide, mountain snow water content was 61 percent of average and 71 percent of last year. East of the Continental Divide, mountain snow water content was 66 percent of average and 88 percent of last year. January through March cumulative precipitation was much below average to above average. Storm activity during January and February in Montana added significant amounts of mountain snow and due to the warmer temperatures the snow was able to carry a lot of moisture. January average temperature departures state-wide were generally 5 to 6 degrees above normal. The above average temperatures carried into February; however, towards the end of the month, record cold air pushed across Montana and the associated snowfall had much less moisture. By March 1, mountain snow water content east of the Continental Divide, was 84 percent of average and 109 percent of last year. The above average precipitation continued into March with a few basins reporting about twice the normal amount. East of the Continental Divide, March mountain and valley precipitation was 133 percent of average and 144 percent of last year. During March valley temperatures were generally above average west of the Continental Divide and generally near to below average east of the Continental Divide. Temperature variations throughout the month caused some low land flooding. January through March inflows were below normal to much below normal. The exception was Lake Sherburne which was 117 percent of average. Inflow for January and February to Bighorn Lake was the lowest on record and January inflow to Clark Canyon was also the lowest on record. April through July: Some drought relief was seen in parts Montana with near to above normal precipitation during February through May. In addition, late snow in the second half of April helped to reduce the 3 snow melt in some basins in Montana. As of April 1, mountain snow water contents statewide were 93 percent of average and 97 percent of last year. West of the Continental Divide snowpack was 92 percent of average and 85 percent of last year. East of the Continental Divide snowpack was 96 percent of average and 115 percent of last year. During April, precipitation varied across the state with mountain areas in the Columbia River basin at 90 percent of average, the Missouri River basin at 126 percent of average and the Yellowstone River basin at 76 percent of average. Overall, April mountain and valley precipitation across the state was 116 percent of average and 130 percent of last year. April temperatures were generally near average in the southwest and above average across other areas of Montana. Precipitation was reduced in May. Mountain and valley precipitation across the state was 85 percent of average and 93 percent of last year, while east of the Continental Divide mountain and valley precipitation was 94 percent of average and 111 percent of last year. May was a month of extremes. Early in the month snow was accumulating in the mountains and record low temperatures were seen in southwest Montana. By the end on the month, temperatures rebounded to record highs with snow melt well above average. The cold temperatures early in the month held on to snow that melted rapidly with the high temperatures later in the month. With above average temperatures there were several areas that reported flooding. Flooding was generally minor and occurred mainly on farm land. As of June 1, remaining mountain snow water contents were generally ranging from near average to severely below average.

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