SWSIReportSept2008

• Title: Colorado Water Supply Conditions Update
• Date: 9/16/2008
• Description: SWSI Report
• Basin: Statewide
• Drought Mitigation - Doc Type: Presentation

SOUTH PLATTE BASIN
Sep - 08

Basinwide Conditions Assessment
The SWSI value for the month was + 3.1 . Reservoir
SOUTH PLATTE BASIN SWSI HISTORY
storage in Dill on, Horsetooth, Eleven Mile, Cheesman,
4
Jackson, and Barr Lake , the major component in this basin
in computing the SWSI value, was 108 % of normal as of the
3
end of August . Cumulative storage in the major plains
reservoirs: Julesbu rg, North Sterling , and Prewitt, is at
2
34.8 % of capacity. Cumulative storage i n the major upper -
DRY INDEX VALUE WET
1
basin reservoirs: Cheesman, Eleven Mi le, Spinney, and
Antero is at 96.3 % of capacity. Flow at the gauging station
0
South Platte River near Kersey was 976 cfs, as compared to
the long - term average of 505 cfs. Flow at the
-1
Colorado /Nebraska s tate line averaged 73 cfs.
Fortunately, August was significantly wetter than the
-2
remainder of the irrigation year on the plains with several
significant widespread storms in the basin. In fact for some
-3
of the plains areas, the rain in August was nearly half of the
total precipitation for the year. The additional supply
-4
Jan-99 Jan-00 Jan-01 Jan-02 Jan-03 Jan-04 Jan-05 Jan-06 Jan-07 Jan-08
provided much needed water directly to crops, reduced the
MONTH / YEAR
need for reservoir supplies and increased stream flow
allowing for junior users to come into priority and begin taking
water. I t even allowed for periods of reservoir refills on the
SOUTH PLATTE RIVER NR. KERSEY, FLOW BY WATER YEAR
plains on the main stem of the South Platte. While storage
conditions by the end of the month were not as good as 2007
3,000,000
at the end of August, there was at least enough storage
water to assure an adequa te supply for most surface water
2,500,000
CUMULATIVE FLOW, Acre-Feet
users this year. Without the wet conditions, some users had
expressed concern that they would not have enough supply
2,000,000
as their rights would have been out - of - priority and/or the
1,500,000
irrigation reservoirs they depend on would hav e been empty
prior to the end of the irrigation season. While not generally
1,000,000
in danger of serious supply limitations this year, municipal
suppliers also benefited from the rains as it reduced their
500,000
demand on reservoir water which will have the affect of
in creasing available supply for future years.
0

Oct Nov Dec Jan Feb March April May June July Aug Sept

WET (1983) DRY (1964) AVG 2008

REPRESENTATIVE RESERVOIRS

300,000

250,000

Usable Storage, acre-feet
200,000
150,000
100,000
50,000
0
Dillon Horsetooth Eleven Mile Cheesman Jackson Barr Lake
Avg. 8/31 Contents 8/31/08 Contents
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