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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Gross generation at the powerplant totaled 36,700,000 kilowatt-hours
for the water year. This was 21,700,000 kilowatt-hours below average.

Willow Creek Reservoir

Completed in 1953, Wi 11 ow Creek Reservoir has a total storage capacity
of 10,600 acre-feet. The uncontrolled spillway, located at the left
abutment, has a capacity of 3,200 ft3/s. The Willow Creek Feeder Canal
begins at the left abutment with a capacity of 400 ft3/s for pumping
to Granby Reservoir.

Reservoir carryover storage coming into water year 1989 was
9,586 acre-feet. This was above the 30-year average of 9,000 acre-feet.

Ouring November, the reservoir was drawndown to near 7,200 acre-feet
to provide storage space for winter inflows. The release to the river
totaled 420 acre-feet, and 2,897 acre-feet was pumped to Lake Granby.
The minimum reservoir content for the water year was 7,173 acre-feet on
November 7. October-January inflows were below normal at only 78 percent
of average. Precipitation for the October-January period was below
average at 78 percent of average.

The February 1 snow-water content was 79 percent of average, which
resulted in an April-July runoff forecast of 40,000 acre-feet.

Precipitation increased
1. 62 inches recorded.
114. percent of average.

During the October through March period, precipitation in the Willow
Creek watershed averaged 91 percent of normal. Snowpack water content
for the April 1 measurement was 76 percent of average. The April-July
snowmelt runoff forecast remained at 40,000 acre-feet or 77 percent of
normal. Inflows continued to be high at 140 percent of normal during
March.

in February to 164 percent of normal with
Inflow was also above normal in February at

The natural inflow increased steadily in April from 19 ft3/s on April 3
to 190 ft3/s on April 27. The total April inflow was much above
normal at 144 percent of average. A total of 5,632 acre-feet was pumped
to Lake Granby during the month. April had below normal precipitation
at 66 percent of average, and the May 1 snowpack water content was only
32 percent of average. This resulted in a lower April-July runoff
forecast of 35,000 acre-feet.

Natural inflow averaged only 199 ft3/s in May and peaked at 290 ft3/s
on May 12. Total monthly inflow was only 54 percent of average. A
total of 9,484 acre-feet was pumped to Lake Granby during May.

June precipitation was below normal at 73 percent of average, and
natural inflow deceased to only 29 percent of average. By the end of
June, inflow had decreased to 40 ft3/s. Precipitation was 81 percent of
average for July, and natural inflow continued to be low at 37 percent
of average. Inflow averaged a low 33 ft3/s for July. Total April-July
inflow was 25,100 acre-feet or 48 percent of average. Conditions

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