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

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HIGHLIGHTS OF 1989 OPERATIONS

Water year 1989 runoff was below average throughout the Colorado-Big
Thompson Project (Project) varying from 55 percent of average for the
inflow into Willow Creek Reservoir to 81 percent of average into Green
Mountain Reservoir.

Peak inflows to reservoirs within the Project occurred in late May and
mid-June and were much below normal. On May 12, inflow to Willow Creek
Reservoir peaked at 290 ft3/s. The inflow to Green Mountain peaked on
May 24 at 1,910 ft3/s. Inflow to Lake Granby peaked at 1,485 ft3/s on
May 30 and the Lake Estes inflow peaked on June 17 at 440 ft3/s.

River releases from Willow Creek Reservoir and Lake Granby were made to
meet only minimum required releases for fish habitat. The maximum
release at Lake Estes for the water year was 305 ft3/s on August 3 to
bypass infl ow. Project deli veri es peaked on August 17 at 769 ft3/s at
Horsetooth Reservoir, and 581 ft3/s at Carter Lake on July 9. The maximum
release at Green Mountain Reservoir was 953 ft3/s on September 5 and the
maximum release of 500 ft3/s to the Big Thompson River occurred on
July 20.

Water year precipitation totals for October-September varied from
80 percent of average on the Willow Creek and Lake Granby watersheds to
87 percent of average on the Lake Estes and St. Vrain watersheds.

Winter precipitation (October-January) was below average on the Project,
at 73 percent of average. The Lake Granby and Wi 11 ow Creek watersheds
received the first significant rain mixed with snowfall of the water
. year on November 3, 4, and 5 with 0.44 inches of precipitation being
recorded. On November 3, the Green Mountai n Dam stat ion recorded
0.29 inches of precipitation due to rain mixed with snowfall. Snow and
rain occurred at Estes Park on November 15 and 0.40 inches of precipitation
was recorded. No sign i fi cant daily snowfall above 0.50 inches was
recorded on the Project in December and January. The Lake Estes
watershed was the only area to record above normal precipitation for
January at 120 percent of average. February was a snowy month on the
Lake Granby and Willow Creek watersheds with 164 percent of average
recorded. The Green Mountai n watershed was al so above average for
February averagi ng 160 percent of normal preci pitat i on. A total of
2.54 inches of precipitation was recorded for the Lake Estes watershed in
February which was much above normal at 488 percent of average.

A major snowstorm hit the Project area from February 2 through February
5, with 1.48 inches of precipitation recorded at Green Mountain, 0.79
inches of precipitation recorded at Lake Granby, and 2.08 inches of
precipitation recorded at Lake Estes.

March snowfall was below normal on all watersheds within the Project with
Lake Estes precipitation at only 15 percent of average. Precipitation
due to snowfall was much below normal on all watersheds on the Project
in April, except for Green Mountain at 123 percent of average.

The maximum snow-water accumulations for all watersheds on the Project
occurred on March 1 and April 1. On the Project, Green Mountain

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