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• <br /> SOUTH PLATTE BASIN <br /> Basinwide Conditions Assessment: <br /> The SWSI value of -0.6 indicates that the current SURFACE WATER SUPPLY INDEX <br /> conditions are slightly below normal and unchanged from the s South Platte River Basin <br /> previous month. Reservoir storage,the key component in this <br /> basin in computing the SWSI value, was 108% of average on ,,,a , (� <br /> ‘.7. ;. <br /> February 1, 1991. Precipitation was 79% of average for the — .: <br /> month of January, and is in a three month decline. Basinwide — _= <br /> snowpack is only 63% of average. There is still time for the 1- �'q, <br /> snowpack to develop as the peak accumulation typically g It' -' `t`+ <br /> - ZC <br /> doesn't occur until around May 1st. Eleven Mile Reservoir <br /> and Antero Reservoir are at 100% of capacity. Cheesman . <br /> a -2- <br /> Reservoir was at 71% of capacity with 55,896 acre-feet in <br /> storage. Releases from Cheesman Reservoir into the South .3 <br /> Platte River are currently at 108 cfs. The majority of ground -4 I <br /> JAN91 JMS2 JANY3 JANB4 JAMBS JAMBE JAN87 JAMB JANB9 JAN90 JAN91 <br /> water recharge projects are operating at near capacity. Flow 4...YEAR <br /> at the key gaging station, South Platte River near Kersey, <br /> averaged 796 cfs for the month of January as compared to the <br /> historic monthly average of 768 cfs. Flow at the <br /> Colorado/Nebraska stateline averaged 625 cfs for the month. <br /> This is a significant increase over the average flow in SOUTH PLATTE RIVER NR. KERSEY <br /> November of 155 cfs. This is the result of irrigation return 450 FLOW BY WATER YEAR <br /> flows below Balzac and a shortage of lower South Platte basin 400 _ P <br /> storage capacity. <br /> 350 <br /> J <br /> 300 <br /> Outlook: <br /> Snowpack in the Saint Vrain basin is only 46% of E 250 <br /> average. Unless above normal precipitation occurs in 2a0 - <br /> February through April in the basin, snowpack going into the F" <br /> 1991 runoff season will likely be 40% below normal. The <br /> streamflow forecast is lowest in the Saint Vrain Creek ,aa <br /> drainage at 65% of average and highest in the Upper South �° f---r <br /> Platte basin at 84% of average. a <br /> act Now aeC Jan Fee Mbren <br /> MONTH <br /> NBC YEAR[i963) + CRY YEAR(1964) o AVG. C 19 <br /> Administrative/Management Concerns: <br /> River calls continue on the South Platte and its <br /> tributaries. Calling rights generally switch from direct flow <br /> uses to storage. The interstate compact with Nebraska South Platte Basin Reservoir Supplies <br /> adjusted on October 15 basically giving Colorado full use of 240 <br /> available streamflow. District 2 (South Platte River between 220- <br /> Denver and Greeley) went to "open river" administration on <br /> January 2, 1991. The river call for District 8 (South Platte 1130 <br /> River above Denver) is the Denver South Platte River intake 18.�� <br /> right (December.6 1910 decree). In addition, the Denver ry' <br /> 12a�\ <br /> Water Department requested the Chatfield Reservoir call g 10.7 \ <br /> (December 12, 1977) to be implemented on January 2, 1991. a Ba 77 <br /> SO <br /> Public Use Impacts: 40 <br /> Public water use should be relatively normal. 0 �-� %� <br /> However, Spinney Mountain Reservoir, one of Colorado's ^ �f\� <br /> alllon Horeetooth Eleven Mlle Cheeenen Jeekeon Barr Lake <br /> premier trout fisheries, was at only 37% of capacity on <br /> Avg. 1/31 contents ® 1/31191 Contents <br /> February 1, 1991, and is currently not in a storing mode due <br /> to the failure and in operation of the Otero Pumping Plant <br /> that would typically be bringing approximately 120 acre-feet <br /> of Homestake transmountain diversion water daily into the reservoir. It is projected that the reservoir contents will drop to <br /> 18,000 acre-feet by April 15, 1991, when direct diversion rights on the South Platte River will commence. Capacity of the <br /> reservoir is 53,651 acre-feet. <br /> 3 <br />