WSP00886

• File Number: 8407
• Description: Platte River Basin - River Basin General Publications
• State: CO
• Basin: South Platte
• Water Division: 1
• Date: 4/16/1990
• Author: BOR
• Title: Annual Operating Plans - North Platte Project Water Years 1989-1990
• Water Supply Pro - Doc Type: Report/Study

Lake Estes

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Completed in 1949, Lake Estes (on the Bi9 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 capability 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
o lympus Tunnels and routed through the F ooth ills 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 69 percent of average. The inflow into
Lake Estes for thi s peri od was also below norma 1 at 65 percent of
average. The February 1 snowpack water content measurement was
78 percent of average which resulted in an April-July most probable
runoff forecast volume of 60,000 acre-feet.

Precipitation over the Big Thompson River basin increased dramatically
in February to 488 percent of average, with 2.54 inches recorded.
I nfl ow increased to 100 percent of average and the March 1 runoff
forecast of the April-July volume increased to 70,000 acre-feet.

Estes Park recorded the second lowest precipitation of 0.12 inches fur
March in 80 years, as precipitation over the watershed decreased rapidly
to only 15 percent of average. The April 1 snow-water content was
8.0 inches or 75 percent of average. The Apri l-Ju ly runoff forecast
volume decreased back to 60,000 acre-feet.

Snowpack in the Big Thompson River Basin was measured at only 51 percent
of average on May 1. Most probable forecasted natural inflow volume to
Lake Estes for the April-July period totaled 45,000 acre-feet, which was
62 percent of average. The May forecast proved to be quite accurate as
actual inflow for April-July was 45,800 acre-feet.

The maximum dai ly inflow of 443 ft3/s occurred on June 17. Natural
inflows decreased in July to 126 ft3/s by July 27. June and July
inflows were 57 percent and 60 percent of average, respectively.

The Big Thompson River inflow that was in excess of the minimum required
outflow below Lake Estes was diverted as skim water through Olympus
Tunnel on April 27 and continued as available until early July.

Due to the high Adams Tunnel diversions that kept Olympus Tunnel at
capacity and the turbine runner replacement at Flatiron Powerplant, Big
Thompson River inflow to Lake Estes was bypassed and not diverted
(sk immed) for power product i on from Ju ly 7 unt i 1 the end of the water
year. Releases to the river below Olympus Dam peaked at 305 ft3/s on
August 3. Water diverted into Olympus Tunnel under operation "skim"

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