WMOD00196

• Contract/Permit #: 2003-01
• Sponsor Name: Gunnison County, City of Gunnison, Crested Butte
• Project Name: WM Evaluation Report
• Title: The Development, Conduct and Evaluation of a Cloud Seeding Program for the Gunnison River Basin, CO During the 2003-04 Season
• Date: 8/1/2004
• County: Gunnison
• State: CO
• Weather Modification - Doc Type: Reports

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4.0 OPERATIONS

The 2002-2003 winter season cloud seeding program for Gunnsion County began on
February 1, 2003 and ended on April 15. A total of 14 storm periods were seeded during a\1 or
portions of 22 days. Six storms were seeded in February, seven in March, and one in April. A
cumulative 1536 hours of operation were logged for a\1 the project CNG sites during the season.
Table 4-1 shows the dates and ground generator usage for the 14 storm events, and Table 4-2
shows operation times for each of the CNG sites.

Precipitation was below normal during the 2002-2003 winter season, totaling about 75-
85% of the normal amount across the Gunnison County seeding target area. The season started
out wet, as a series of early November storms brought substantial snows to the Colorado
mountains. However, the period from mid-November through mid-February was generally
dominated by a ridge of high pressure and dry weather, with less than half the normal amount of
precipitation. Normal snowfall resumed in mid-February and continued through the spring.
Temperatures, on average, were near their normal values for the winter season. Figures 4.1 to
4.3 show snow water content and precipitation, and normals, at three SNOTEL sites for the
2002-2003 winter season.

4.1 Operational Procedures

In operational practice, an approaching storm was monitored at the NA WC operations
center in Salt Lake City, utilizing online weather information. If the storm met the seedability
criteria presented in Table 2-5, and if no seeding curtailments or suspensions were in effect, an
appropriate array of seeding generators was ignited and adjusted as conditions required. Seeding
continued as long as conditions were favorable and precipitating clouds remained over the target
area. In a normal sequence of events, certain generators would be used in the early period of
storm passage, some of which might be turned off as the wind direction changed, with other
generators then used to target the area in response to the evolving wind pattern. Wind direction

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