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Wyoming Area Office <br />Bureau of Reclamation <br />North Platte River Water Supply Update <br />November 8, 2010 <br />Pagel of 3 <br />Figure 1 shows current reservoir storage conditions for Reclamation reservoirs on the North <br />Platte River as of November 4, 2010, and provides a comparison of total inflow, total Guernsey <br />Reservoir outflow, and total September 30 system storage for water years 2007 through 2010, <br />including the statistical "most probable" 2011 operations compiled from the November operating <br />plan. The term "kaf ' used in this report represents acre -feet times 1000. <br />The North Platte total system storage of 2024.2 kaf (143% of average) at the end of water year <br />2010 represents an increase in the system storage of 323.8 kaf over water year 2009 (1700.4 kaf). <br />This system storage increase is attributable to well above average runoff into the North Platte <br />River Basin above Guernsey Reservoir of 2077.0 kaf or 154% of average. Releases from <br />Guernsey Reservoir were discontinued on September 21, 2010. The North Platte Project <br />Irrigation Districts ended the water year with 695.3 kaf (170% of average) of carryover storage, <br />which is above the 30 -year (1981 -2010) average carryover storage of 409.0 kaf for September <br />30. <br />The inflow into Seminoe Reservoir exceeded 15,000 cfs for nine (9) consecutive days in June, <br />with an all time peak of 19,376 cfs on June 15th. The previous peak Seminoe inflow was 17,099 <br />cfs on June 27, 1983. Pathfinder Reservoir reached a peak elevation of 5852.05 feet on June 22, <br />2010, approximately two (2) feet above the existing spillway crest of 5850.10 feet. Flows over <br />the uncontrolled spillway began on June 15th and continued for 28 days. The flow over the <br />spillway reached a peak of over 4000 cfs on June 22nd. Releases from Gray Reef Reservoir <br />reached 7000 cfs for a period of two (2) days (June 23 -24). Flow in the North Platte River at <br />Casdper., Wyoming, peaked at 7160 on June 24. Glendo Reservoir entered the flood pool on May <br />23r and remained there for 76 days. Glendo Reservoir reached a peak elevation of 4648.83 feet <br />on June 29, 2010, exceeded only in 1973 (elev. 4651.90 feet) and 1984 (elev. 4650.27 feet). The <br />uncontrolled spillway crest elevation at Glendo Dam is 4653 feet. <br />Because of the significant inflows, high reservoir contents, and high reservoir releases <br />throughout the North Platte Reservoir system, Reclamation conducted extensive coordination of <br />reservoir operations with counties, emergency management entities, Army Corps of Engineers, <br />Wyoming State Engineers Office, Nebraska Department of Natural Resources, and other state <br />and local entities in Wyoming and Nebraska through conference calls held up to three times per <br />week during June and July. <br />The total system probable inflow for water year 2011, which approximates an average inflow <br />condition is estimated to be 1351.6 kaf. The total Guernsey Reservoir probable outflow for 2011 <br />is estimated to be 1245.3 kaf. The projected total system probable storage on September 30, <br />2011, is estimated to be 133% of average (1887.4 kaf /1420.6 kaf) or 67% of the total <br />conservation capacity of the system. <br />