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SOUTH PLATTE BASIN Basinwide Conditions Assessment The SWSI value for the month was +1.0. Reservoir storage in billion, Horsetooth, Eleven Mile, Cheesman, Jackson, and Barr Lake, the major component in this basin in computing the SWSI value, was 99% of normal as of the end of September. Cumulative storage in the major plains reservoirs: Julesberg, North Sterling, and Prewitt, is at 74% of capacity. Cumulative storage in the major upper-basin reservoirs: Cheesman, Eleven Mile, Spinney, and Antero is at 92% of capacity. Flow at the gaging station South Platte River near Kersey was 408 cfs, as compared to the long- term average of 1745 cfs. Flow at the Colorado/Nebraska state line averaged 110 cfs. Outlook With dry conditions on the plains during May, flows on tributaries and the mainstem remained below average. As a result, there was a direct flow call for irrigation the duration of May. While this is not unusual, it does create concerns about the adequacy of irrigation supplies later in the summer for some users, especially on the mainstem, as they had to use their reservoir supplies for their crops. At the same time, snowpack remained above average. Nevertheless, it is questionable how high the runoff will be on the mainstem without significant rainfall. Water supply on the tributaries should be in better shape as users on the tributaries have the senior rights and will be able to use the expected runoff. Likewise, municipal users should generally be in good condition as they generally have a higher watersupply safety factor. Jun-08 JJIJTH PLATTE 6ASIN SWSI HISTORY 4 3 2 W ~, W J Q X W 0 -, 0 -2 -3 Jan-99 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08 MONiHIYEAR SOUTH PLATTE RIVER NR. KERSEY, FLOW BY WATER YEAR 3,000,000 ~ 2,500,000 m L Q 2,000,000 0 ~ 1,500,000 W ~ 1,000,000 U 500,000 0 Oct Nov Dec Jan Feb March Apnl May June July Aug Sept ~ WET (1983) ~ DRY (1964) ~ AVG ~ 2008 3