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Wyoming Area Office <br />Bureau of Reclamation <br />North Platte River Water Supply Update <br />April 22, 2011 <br />Page 1 of 2 <br />Figure 1 shows current reservoir storage conditions for Reclamation reservoirs as of April 20, <br />2011, on the North Platte River and provides a comparison of total inflow, total Guernsey <br />Reservoir outflow, and total September 30 system storage for water years 2008 through 2010, <br />including the "expected" 2011 operations compiled from the April operating plan. The term <br />"kaf' used in this report represents acre -feet times 1000. The North Platte total system storage <br />of 2024.1 kaf at the end of water year 2010 represents an increase in the system storage of 323.7 <br />kaf over water year 2009 (1700.4 kaf). This system storage increase is attributable to above <br />average snowmelt runoff in the upper and lower North Platte Basins. Irrigation releases from <br />Guernsey Reservoir for downstream irrigation demand were discontinued on September 20, <br />2010. The North Platte Project Irrigation Districts conserved approximately 695.3 kaf of <br />carryover storage. <br />The total system expected inflow for 2011 is estimated at 2239.1 kaf or 166% of average. The <br />total Guernsey Reservoir expected outflow for 2011 is estimated to be 1994.0 kaf. The projected <br />total system expected storage on September 30, 2011, is estimated to be 141 % of average <br />(2002.9 kaf /1420.6 kaf) or 72% of the total conservation capacity of the system. <br />Figure 2 and Figure 3 provide snow water equivalent (SWE) information expressed in inches of <br />water for the upper and lower North Platte River basins. The SNOTEL information shows the <br />SWE is above average for the upper North Platte River Basin and at average for the lower North <br />Platte River Basin. As of April 21, 2011, the Natural Resources Conservation Service (MRCS) <br />reported the SWE to be 157% and 126% of average (Figure 4) for the upper and lower basin, <br />respectively, thanks to recent snow storms. Reclamation's April 1 forecast of the April through <br />July runoff in the basin above Seminoe Reservoir is 1,450 kaf (203% of average) and 180 kaf <br />(137% of average) for the basin between Alcova and Glendo Reservoirs. The NRCS SWE data <br />on March 31, 2011 were 137% and 115% of average for the upper and lower North Platte River <br />basins, respectively, when these forecasts were made. The SWE for the upper North Platte River <br />Basin is the highest of record in the last 30 years. Reclamation's determination of the forecasted <br />supply as of April 1 is above 1,100 kaf (Figure 5), which indicates at this time there is no need to <br />allocate storage. <br />Table 1 shows the actual total system inflows, Guernsey outflow, and end -of -month total system <br />storage for the month of October through March and the projected April through September <br />operations based on minimum, expected, and maximum inflow conditions. These inflow <br />conditions (Table 2) provide the range for Reclamation operating plans in the North Platte River <br />Basin. The operating plans are updated monthly to reflect changing inflow conditions. This <br />report focuses on the information associated with the April expected operating plan. <br />Table 1 also includes the accompanying information for water year 2010 and the 30 -year average <br />