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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average. Due to much above normal temperatures, April inflow was high
at 165 .percent of average. However, April was a dry month as
precipitation was 66 percent of average. The May 1 snowpack was only
50 percent of average, which further decreased the April-July runoff
forecast volumne to 155,000 acre-feet. Inflows rose sharply in mid-May
and peaked for the water year at 1,486 ft3/s on May 30.

With water pumped from Willow Creek and natural inflow on the rise,
storage began a gradual cl imb reaching 343,245 acre-feet by May 31.
May continued to be dryas precipitation was only 57 percent of average.

Natural inflow decreased rapidly in late June to below 500 ft3/s by the
end of the month. Preci pitat i on continued be low normal for June at
73 percent of average, as well as inflow at only 52 percent of average.
Lake Granby storage continued to rise reaching its maximum for the
season of 374,644 acre-feet on June 23. This was 165,156 acre-feet
below maximum storage capacity.

Natural inflows continued. to be low in July at only 47 _percent of
average. By mid-month, natural inflow averaged only 225 ft3/s. Total
release to the Colorado River was equal to the bypass release for minimum
requi red fi sh habitat release, and thi s was decreased by 25 percent
due to the low runoff.

During July, Adams Tunnel diversions remained high at 30,700 acre-feet
to meet project water del iveries which were much above average and to
maintain desirable storage levels in Carter Lake and Horsetooth
Reservoirs. For August, diversions through Adams Tunnel were increased
to capacity at 33,800 acre-feet for the month to maintain terminal
reservoir storage and to meet near normal irrigation deliveries.
Conditions improved in August as inflows averaged 105 percent of average
and precipitation was 79 percent of average.

During September, natural inflows were 79 percent of average, and
precipitation was only 53 percent of average. Adams Tunnel diversions
continued high at 30,700 acre-feet for the month, 180 percent of average.

A total of 4,020 acre-feet of water was pumped into Lake Granby during
June via Windy Gap Pumping Plant for the 1989 water year.

The computed April-July natural inflow to Lake Granby totaled
133,500 acre-feet. This was between the May 1 reasonable mlnlmum
(120,000 acre-feet) and May most probable (155,000 acre-feet> runoff
forecasts for the April-July volume. The May-July precipitation was
only 70 percent of average which resulted in the low runoff.

Lake Granby ended the water year wi th 301,182 acre-feet of water in
storage. This was 118,318 acre-feet above average and 124,170 acre-feet
less than last year.

Adams Tunnel diversions totaled 276,700 acre-feet for the water year.
This was more than 42,200 acre-feet above average.

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