WSP03460

• File Number: 8441.700
• Description: Colorado Big Thompson Project - Annual Operating Plans
• Basin: South Platte
• Water Division: 1
• Date: 1/1/1989
• Title: Annual Operating Plans - Colorado Big Thompson Project - Water Year 1989-1990
• Water Supply Pro - Doc Type: Report/Study

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ANNUAL OPERATING PLAN AFTER FEBRUARY 1

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Most Probable Inflow For-ecast

Colorado-Big Thompson Project

Green Mountain Reservoir-

Tur-bine releases for replacement, bypass of inflow, power, and reser-voir
regulation wi 11 approximate 150 ft3/s during Febr-uar-y and Mar-ch. If
most probable runoff conditions develop, releases will be increased to
340 ft3/s dur-ing Apr-il to achieve the desired stor-age tar-get of
65,UOO acre-feet at the end of April.

As the reser-voir- fills during the May-July r-unoff per-iod, releases will
be adjusted to achieve a fill without spill during the ear-ly part of
July. With normal inflow and near-average releases for downstr-eam water
users dur-ing August and September-, storage is projected to be about
135,000 acre-feet by the end of September.

With most pr-obable runoff conditions, Denver and Colorado Spr-ings'
Blue River depletions are projected to be about 52,200 acr-e-feet dur-ing
the February-September period. These depletions would cause about
12 gigawatt-hour-s of power inter-fer-ence at Green Mountain Powerplant.

Willow Cr-eek Reservoir

Under- the most probab le cond it ions, Wi 11 ow Cr-eek Reservoi r- wi 11 fi 11 to
about 10~UOO acr-e-feet by the end of June. The minimum required releases
of 7 fV/s to the river dur-ing February, March, and April, 24 ft3/s
during May, and 44 ft3/s during June will be maintained. During Apr-il
thr-ough September-, approximately 43,900 acre-feet will be pumped to
Lake Granby. While maintaining the required river- release for downstr-eam
water- rights, Willow Creek storage will be near 9,000 acre-feet at the
end of the water year.

Lake Granby

Lake Granby storage will be lowered to 130,800 acre-feet by the end of
March. With most probable inflow, stor-age is expected to reach
287,400 acre-feet by the end of July. This is 252,400 acr-e-feet below
maximum reservoir storage, only 65 percent of average and the lowest end
of July storage since 1977. Gr-anby Reservoir content of about
258,500 acr-e-feet at the end of the water year will be only 62 percent of
average.

East Slope/Color-ado-Big Thompson Project

If climatic conditions pr-oduce most probable inflow, a near normal
supplemental irrigation demand equal to 264,900 acre-feet would be
expected on the Project. Adams Tunnel diversions will be at capacity
from Febr-uary 1 through March 20, averaging 550 ft3/s due to below normal