WMOD00011

• Applicant: Don Griffith North American Weather Consultants, Inc.
• Sponsor Name: City and County of Gunnison
• Project Name: Cloud Seeding Evaluation
• Title: The Development, Conduct and Evaluation of a Cloud Seeding Program for the Gunnison River Basin, Colorado During the 2003-2004 Season
• Prepared For: City and County of Gunnison
• Prepared By: North American Weather Consultants
• Date: 8/1/2004
• County: Gunnison
• Weather Modification - Doc Type: Report

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3.0 OPERATIO:\S

The 2003-1004 winter season cloud seeding project for Gunnison County began on
November 15.2003 and ended on April 15.2004. A total of 20 stonn periods Y./ere seeded
during all or portions of 31 days. Three storms were seeded in Xovembcr. five in December.
three in January. five in February. two in March. and [\1."0 in April. A cumulative 3.299 hours of
operation were conducted during the season. releasing 39.588 grams of silver iodide. Table 3-1
shows the dates and ground generator usage for the 20 stann events. and Table 3-1 shows
operation times for each of the C\'G sites.

Precipitation was agam somc\vhat below nonnal in most areas of western Colorado
during the 2003-2004 ,,,'inter season, totaling about 80-100% of the nonnal amount across the
Gunnison County seeding target area, As of April 15. Gunnison Basin S1'o:OTEL sites averaged
91 % of the nonnal water year precipitation. and only 78% of average snow \"'ater content. The
low snow water content was largely a result of wann weather in March that led to substantial
melting. The higher precipitation and snowpack amounts were generally in the southern portion
of the basin. particularly in the vicinity of the San Juan Range. where precipitation over the
season was close to nonnal.

The 2003-2004 season started out close to nonnal. except for a dry October (when rain or
melting sno'\/ usually occurs). which caused water year precipitation totals to start out below
nonnal. For this reason. water year precipitation totals and snow water content ";ere very similar
throughout most of the season. Precipitation (snowfall) was very close to nonnal in 1'o:0vember
and December. A series of heavy stonns al the end of December and beginning of January
broughl about 3-5" of waler equivalent to most of the target area. bringing both ,I,'ater year
precipitation and snow water content to above average levels. The weather pattern was generally
dry during the remainder of January and most of February. causing water year precipitation (and
in some areas snow water content) 10 drop 10 somewhat less than a\'erage values. A series of
heavy storm events in the southwestern U.S. during late February brought as much as 5" of water
equi,'alent to portions of southwestern Colorado. particularly the San Juan Range. and brought

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