WSP09032

• File Number: 8407
• Description: Platte River Basin - River Basin General Publications
• State: CO
• Basin: South Platte
• Water Division: 1
• Date: 2/27/1991
• Author: BOR
• Title: Annual Operating Plans - North Platte Project Water Years 1990-1991
• Water Supply Pro - Doc Type: Report/Study

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 wi th 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.

totaled
probable

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During September, natu~al inflows were 114
precipitation 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.

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

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

Lake Estes

Completed in 1949, Lake Estes (on the Big Thompson River) provides
regulating capacity for power purposes. The lake has a total capacity of
3,100 acre-feet and controls the discharge of Estes Powerplant, river
inflow, river outflow, and releases of water to the Foothills Power System
via Olympus Tunnel (550 ft3/s capacity). The Estes Powerplant contains
three units with a total installed capacity of 45 megawatts, with combined
release capability of 1,300 ft3/s. The spillway, located on the right
abutment, has five radial gates with a total release capabil ity of
21,200 ft3/s. The center gate has been automated and is controllable from
the Flatiron Control Center.

During the winter, project water is diverted through Adams and Olympus
Tunnels and routed through the Foothills Power System on its journey to
terminal storage in Carter Lake and Horsetooth Reservoir.

The October-January precipitation for the Big Thompson River Basin above
Lake Estes was below normal at 74 percent of average. The inflow into Lake
Estes for this period was also below normal at 75 percent of average. The
February 1 snowpack water content measurement was 64 percent of average
whi ch resulted in an April-July most probabl e runoff forecast vol ume of
58,000 acre-feet.

Precipitation 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 volume remained at 58,000 acre-feet. .

Estes Park recorded the sixth highest precipitation of 3.06 inches for
March in 81 years of record, as precipitation over the watershed increased
rapidly to' 243 percent of average. A major snowstorm on March 6, 1990,
deposited 1 to 3 feet of wet snow along the front range. The April 1
snow-water content was 12.4 inches or 115 percent of average. The
April-July runoff forecast volume increased to 77,000 acre-feet.

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