WSP09277

• File Number: 8441.700
• Description: Colorado Big Thompson Project - Annual Operating Plans
• Basin: South Platte
• Water Division: 1
• Date: 1/1/1998
• Title: Annual Operating Plans - Colorado Big Thompson Project and Western Division System Power Operations - Water Year 1998 Summary of Actual Operations
• Water Supply Pro - Doc Type: Report/Study

SUMMARY OF 1998 OPERATIONS

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Water year 1998 precipitation totals for October-September were above average on the east slope and
slightly below average over the west slope. The east slope percentages of average ranged from 104 on
the Poudre River watershed to 124 for the Lake Estes and St. Vrain watersheds. Along the west slope,
percentages varied from 94 percent for the Willow Creek and Lake Granby watersheds, to
97 percent for the Green Mountain Reservoir watersheds.

Winter precipitation over the Colorado-Big Thompson Project (Project) region for the period of October
to January was relatively low, with only 84 percent of average for all the stations. brought extremely dry
weather to the region. Green Mountain Dam received only 0.47 inches of precipitation during January,
which represents37 percent of average. The stations along the east slope measured well below average
precipitation also. During December, the Lake Estes and St. Vrain watersheds received an average of
0.32 inches of precipitation, only 44 percent of average. January 6 snowpack totals were below average
over the Upper Colorado Basin, Upper Colorado Headwaters and the South Platte. The Upper .and
Lower North Platte also reported low snowpack values. February 2 snowpack totals were also below
average.

Temperatures in the region for January were generally above average. The highest temperature recorded
at Fort Collins for January was 640F on January 2. Precipitation was also above average, with average
reported as high as 168 percent of average for the Poudre basin. By February the weather turned dry
again, as precipitation reported was below the percent of average, ranging from 67 percent over the
Willow CreeklLake Granby watershed, to 139 on the Poudre. Temperatures were generally near to
above average during the month of Febrnary.

March 1 snowpack was 94 percent of the 1966 - 1995 average throughout the Project watersheds.
March was fairly typical with rain, wet snow, some sunny weather, warm days, cold days, and plenty of
wind. Precipitation for March was well below normal over the West Slope and well above average over
the East Slopes. The Willow Creek and Lake Granby watersheds were the loweSt at
39 percent of average. Green Mountain Reservoir reported the highest total precipitation, at
98 percent of average for all the combine stations in the watershed. Temperatures over the region were
varied, although March 24 brought unexpected warm weather. Numerous high temperature records were
tied or broken across the state that day, with Fort Collins recording 760F, Pueblo 770F, Alamosa 680F
and Colorado Springs 71 OF.

During the month of April, precipitation continued to be scarce across the western slope of the CBT,
recording only 70 percent of average the all the stations. By contrast, the eastern slopes recorded much
higher rainfall totals. The average precipitation for the combined recording stations along the eastern
slopes was 1.55 percent of average. The Willow Creek and Lake Granby watersheds were the lowest of
all the station along the project, at only 52 percent of. average. The Lake Estes and
St. Vrain watersheds were the highest, measuring 169 percent of average. Temperatures in the region
were varied during April. The city of Fort Collins and surrounding areas were warmer than normal
during April. On April 11, the City of Fort Collins tied a 15-year-old record high temperature, measuring
80oF.

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