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

remained dry through September and by the end of the water year, natural
inflow averaged only 13 ft3/s. Water pumped to Lake Granby totaled
3,065 acre-feet for June, no water was pumped in July, and
2,168 acre-feet for August.

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A total of 872 acre-feet of water in excess of downstream irrigation
demands and minimum required fish releases was bypassed during the year.

During water year 1989, a total of 21,810 acre-feet was pumped to Lake
Granby. Inflow to the reservoir during the water year totaled
33,100 acre-feet which was only 55 percent of average.

On September 30, the reservoir had 8,194 acre-feet of water in storage.

Granby Reservoir

Completed in 1950, the Granby Reservoir on the upper Colorado River
collects and stores most of the project water supply for the Project.
The reservoir stores the flow of the Colorado River as well as water
pumped from Willow Creek Reservoir. The reservoir has a total storage
capacity of 539,800 acre-feet. The spillway, located on the left
abutment, is controlled by two radial gates with a total release
capacity of 11,500 ft3/s. Granby Pumping Plant has three units with
a combined installed capacity of 600 ft3/s.

Reservoi r carryover storage into water year 1989 was 425,352 acre-feet
which was slightly above the 30-year average of 419,500 acre-feet.

January was below normal, as precipitation was 77 percent of average and
reservoir inflow was 76 percent of average.

The required minimum reservoir release of 20 ft3/s for fish habitat
was maintained throughout the October-January period.

The February 1 snowpack water content was recorded at 86 percent of
average, resulting in a April-July runoff forecast of 185,000 acre-feet.
February was wet at 164 percent of normal precipitation, and 110 percent
of average inflow. The March 1 snowpack water content was 93 percent of
average which slightly increased the April-July runoff forecast to
190,000 acre-feet. Dry conditions returned in March, as precipitation
was 91 percent of average:

Adams Tunnel diversions to the east slope and reservoir storage remained
close to plan through February. The diversions were shutdown for 11 days
in mid-April due to scheduled annual maintenance on Olympus Tunnel
and Pole Hill Powerplant.

April 1 snowpack declined to 79 percent of average, and the April-July
runoff forecast volume decreased to 165,000 acre-feet.

Lake Granby storage cont i nued to decl i ne unt il April 14 when mi n imum
storage for the year was reached at 303,265 acre-feet (water surface
elevation 8242.96 feet). Granby storage continued to be above normal as
the April 30 storage level was 15,922 acre-feet above the 1959-1985

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