WSP09032

• File Number: 8407
• Description: Platte River Basin - River Basin General Publications
• State: CO
• Basin: South Platte
• Water Division: 1
• Date: 2/27/1991
• Author: BOR
• Title: Annual Operating Plans - North Platte Project Water Years 1990-1991
• Water Supply Pro - Doc Type: Report/Study

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000974 .

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 25 and continued as available through September.

Snowpack in the Big Thompson River Basin was measured at 9.9 inches or
93 percent of average on May 1. Most probable forecasted natural inflow
volume to Lake Estes for the April-July period decreased to
70,000 acre-feet, which was 85 percent of average. The May forecast proved
to be quite accurate as actual inflow for April-July was 69,400 acre-feet.

The maximum daily inflow of 968 ft3/s occurred on June 12, and this was
114 percent of the 30-year average. June was extremely hot and dryas
precipitation was only 17 percent of average with 0.33 inches recorded;
the 8th lowest monthly total on record in 81 years. Natural inflows
decreased to 158 ft3/s by July 31. June and July inflows were 110 percent
and 84 'percent of average, respectively.

Due to the low Adams Tunnel diversions and low irrigation deliveries, most
of the Big Thompson River inflow to Lake Estes was diverted (skimmed) for
power production. Releases to the river below Olympus Dam peaked at
370 ft /s on June 13. Water diverted into Olympus Tunnel under operation
"skim" totaled 42,809 acre-feet for the year and this resulted in
76 gigawatt-hours of generation. This was 105 percent of the average
40,700 acre-feet annually diverted.

July and August precipitation at Lake Estes was much above normal at
189 percent of average and 141 percent of average, respectively. Total
precipitation for the water year (October-September) was 19.59 inches or
113 percent of average. The inflow above Lake Estes was 89,800 acre-feet
for water year 1990 and this was 130 percent of average.

Estes Powerplant generation totaled 95,600,000 kilowatt-hours for the water
year and was 11,200,000 kilowatt-hours below average. This was due to the
below average Adams Tunnel diversions which were 92 percent of average.

Carter Lake

Completed in 1952 with three dams, Carter Lake has a total storage capacity
of 112,200 acre-feet. Inflow of project water to Carter Lake is from the
Flatiron Pumping Plant with a capacity of about 400 ft3/s.

Carter Lake storage content at the beginning of the water year was
36,450 acre-feet which was below the 30-year average of 51,000 acre-feet.
Project water deliveries to the St. Vrain Canal continued through the end
of October and totaled 10,421 acre-feet for the month. .

Continuous pumping to Carter Lake from Flatiron Reservoir continued until
mid-October to accommodate scheduled Charles Hansen Feeder Canal {550 ft3/s
section) maintenance during the October 1 to October 12 period. Pumping
to Carter Lake was shut down on October 19 due to the high del iveries
(400 ft3/s) to the Big Thompson River and to have a desirable inflow to
Horsetooth Reservoir. Pumping began again on November 3 and continued
through March 17 when Pole Hill Powerplant was shut down for maintenance.

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