WSP00432

• File Number: 8441.700
• Description: Colorado Big Thompson Project - Annual Operating Plans
• Basin: South Platte
• Water Division: 1
• Date: 1/1/1990
• Title: Annual Operating Plans - Colorado Big Thompson Project - Water Year 1990-1991
• Water Supply Pro - Doc Type: Report/Study

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During September, natural inflows were 114
precipitatipn was 119 percent of average.
. continued low at 7,400 acre-feet for the month,

percent . of average and
Adams Tunnel diversions
43 percent of average.

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A total of' 14,442 acre-feet of water ~Ias pumped into Lake Granby from
May 16 thro~gh June 30 via Windy Gap Pumping Plant for the 1990 water year.

The computed Apri l-July natural i nfl ow to Lake Granby
200,300 acre-feet. This was near the May 1 most
(195,000 acre-feet) runoff forecast for the April-July volume.

Lake Granby ended the water year with 295,791 acre-feet of water in
storage. ! This was 120,109 acre-feet below average, but only
5,391 acre-feet less than last year.

Adams Tunnel diversions totaled 216,800 acre-feet for the water year. This
was more than 17,800 acre-feet below average.

totaled
probable

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Lake Estes

Completed in 1949, Lake Estes (on the Big Thompson River) provides
regulating tapacity for power purposes. The lake has a total capacity of
3,100 acre-lfeet and controls the di scharge of Estes Powerpl ant, ri ver
inflow, river outflow, and ~elea:ses of water to the Foothills Power System
vta Olympus! Tunnel (550 ft Is capacity). The Estes Powerplant contains
three units lwith a total installed capacity of 45 megawatts, with combined
release cap~bility of 1,300 ft3jS. The spillway, located on the right
abutment, Has five' radial gates with a total release capabil ity of
21,200ft3jS. The center gate has been automated and is controllable from
the Flatiro~ Control Center.

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During the ~inter, project water is diverted through Adams and Olympus
Tunnels andi routed through the Foothills Power System on its journey to
terminal st9rage in Carter Lake and Horsetooth Reservoir. '

The OctobertJanuary precipitation for the Big Thompson River Basin above
Lake Estes l'ias below normal at 74 percent of average. The inflow into Lake
Estes for tijis period was also below normal at 75 percent of average. The
February 1 ~nowpack water content measurement was 64 percent of average
which resul~ed in an April-July ,most probable runoff forecast volume of
58,000 acre~feet. ,

PrecipHatiqn over the Big Thompson River Basin in February was 88 percent
of average.! Inflow was 86 percent of average and the March 1 runoff
forecast of ' the April-July vol ume remained at 58,000 acre-feet.

Estes Park ,recorded the sixth highest precipitation of 3.06 inches for
March in 81 ~ears of record, as preci pi tat i on ov, er the watersh,ed increased
rapidly to ?43 percent of average. A major snowstorm on March 6, 1990,
depos Hed 1 i to 3 feet of wet snow along the front range. The April 1
snow-water ~ontent was 12.4 inches or 115 percent of average. The
April-July ~unoff forecast volume increased to 77,000 acre-feet.

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