DWR_4151882

• Title: AUGUST 1994 SWSI: COLORADO WATER SUPPLY CONDITIONS UPDATE, SURFACE WATER SUPPLY INDEX
• Year: 1994
• Document Type - Publications and Reports: SWSI Monthly Report

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SOUTH PLATTE BASIN
Basinwide Conditions Assessment:
The SWSI value of 0.2 indicates that for July the basin SOUTH PLATTE RIVER BASIN
Surface Water Supply Index History
ater supplies were near normal. Reservoir storage, the key S
component in this basin in computing the SWSI value, was 4_
91% of normal on July 31. Storage in the major plains 3_
-
reservoirs, Julesburg, North Sterling, and Prewitt, decreased "� _ 4
by 36,438 acre-feet during July and are at 40% of capacity. 2 -r ±r- ii- :11:14.
qStorage in the major upper basin reservoirs,Cheesman,Eleven ._.,.. -
Mile, Spinney, and Antero, decreased by 13,078 acre-feet and i n �'
o flow of the South
are at 94/o of capacity. The mean daily ,_ I
Platte River at the Kersey gage was 182 cfs, as compared to a
the 1961-1993 July average of 839 cfs. Flow at the °
Colorado/Nebraska state line averaged 32 cfs. 3
The month of July continued the summer trend of -4 ""'
JAN85 JAN86 JAMB, JAN88 JAMBS JAN90 JAN91 JAN92 JANO3 JAN94
being very dry with only isolated precipitation events which NONTH/YEAR
are not particularly helpful in maintaining stream flows. To
make up for low stream flows irrigators have been very
dependent upon both wells and reservoir storage to water
their crops. In isolated situations where wells and reservoir
water is not available, reduction of yield and even loss of SOUTH PLATTE RIVER NR. KERSEY
FLOW BY WATER YEAR
crops have been experienced. Mitigating in part for the low 2.
water situation, the hot weather has accelerated crop growth 2.8 -
2.4
to the point where crops are almost two weeks ahead of 2.2
schedule. i: 2
t 1.8
Administrative/Management Concerns 0 1.4
The dry conditions have created more senior calls . 1.2 -
-aan usual. The call on the South Platte mainstem in District 1
during July was 1866 which is the most senior call since i ..8 -
during the 1970's. The draft upon many of the irrigation 4 —
supply reservoirs located on the plains has lowered the levels 0.2 I • a •
of these reservoirs dramatically to where in some cases they 0
Oct Nov Dec Jan Feb Perch Apell Nay Ju» July Aug Sept
may not contain enough water to finish irrigating crops. One MGN>,1
O WET Catlin) o CRY(1964) A AVG % 1884
or two significant rain events in August would improve the
water supply situation. In contrast to the plains irrigation
reservoirs, most of the mountain municipal
reservoirs have not yet been drawn down.
REPRESENTATIVE RESERVOIRS
SOUTH PLATTE RIVER BASIN
Outlook 2G0
Irrigators will be especially vulnerable if there are 2,0
continued low flow conditions which do not allow plains n0
2�
reservoirs to refill during the winter. Such a situation coupled i 1Bo
with a second year of low runoff and no rain next spring a r, ,ag
would create severe shortages for irrigators next year. 3 140
Continued dry conditions for another year may also begin to h F in7
affect the supplies for municipalities. 10p
The U.S. Forest Service has issued land-use i A 7-A
authorizations for four reservoirs in the Cache la Poudre 40 ,7.\-7.
drainage. These authorizations are conditional upon a joint
operation plan designed to maintain 20 cfs in the Cache la
01118. IbrMtooth Eleven Mlle Chaa.an Jackson Barr Lake
Poudre at Rustic from December through March. Bypass flows
® Avg '"'Contents ® 7.31/84°onta.rca
were required below Joe Wright Reservoir of at least 3 cfs
between April 1 and September 30,and 1 cfs between October
and March 31. All authorizations are also dependent upon
establishment of a program to reduce adverse effects of reservoir operation on endangered species along the Platte River.
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