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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2.~ Equipment and Proieet Set-lip

The size of target area for 2003-2004 was approximately double that of the prior
season, expanded to include portions of the watershed that are south of Gunnison County.
The contract period for seeding operations was :\"O\'ember 15. 2003 through April 15.
2004. The existing network of cloud nuclealing generators (CNG's) was expanded from
the original 18 sites to a total of 27 sites by the end of the 2003-2004 winter season.
These new sites were located where they would be of value in seeding the southern
portion of the target area. Additionally. one of the original C\'G siles (Black Mesa
lodge) was replaced by a site further north (Crawford) along the western side of
Gunnison County. The existing Crawford site was renamed "Crawford South", Figure
2.1 is a map showing the seeding target areas and CNG sites. Table 2-2 lists the names,
latitude and longitude and elevation infomlation for these sites. Figure 2.2 is a photo of a
ground-based C:\G. similar to those used in the Gunnison County pro,b'Tam.

The cloud seeding equipment consisted of a cloud seeding generator unit and a
propane gas supply, The seeding solution used in the 2003-2004 program contained 3%
silver iodide. rather than the 2% solution used during the previous season. This change
was made to increase the output of cloud seeding nuclei. The solution consists of
acetone. silver iodide. sodium iodide and para-dichlorobenzene. The seeding solution
contains three percent (by weight) silver iodide (Agl). the active seeding agent.
complcxed with very small portions of sodium iodide and para.dichlorobcnzene in
solution with acetone. Dr. William Finnegan of the Desert Research Institute published a
paper (Finnegan. 1999) suggesting that this fonnulation is superior to those that produce
pure silver iodide particles upon combustion, The modified panicles act as ice-forming
nuclei much more quickly. and there are somewhat larger numbers of etTective nuclei at
wanner temperatures (e.g. about -5 to -1 DC).

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