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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5.0 SUMMARY A:-Ol> RECO~IME:-OI>ATlO:-OS

A ne"..' cloud seeding project was organized to benefit Gunnison County during the 2002-
2003 winter season. North American Weather Consultants (NA We) was selected as the
contractor to perform that work. This project was continued for the 2003-2004 winter season.
The project target area was expanded for this second season of operations to include tributaries
that drain areas in the southern part of the upper Gunnison River Basin. A second cloud seeding
permit, which is valid for a five year period, was obtained from the Colorado Water
Conservation Board to add this expanded area. Sevcrallocal sponsors joined together to obtain
the [unds required to organize and conduct this project. Sponsors include: City of Crested Butte,
City of Gunnison, Crested Butte Mountain Resort, Crested Butte South Metropolitan District,
Dos Rios Water System, Gunnison County, Gunnison County Stock Growers Association, Upper
Gunnison River Water Conservancy District and Scenic River Tours,

Twenty.seven ground-based, manually operated silver iodide generators were installed
for the project. Twenty storm periods were seeded during the operational period of November
15,2003 - April 15,2004. A total of 3.299 generator hours \\-"ere utilized resulting in the release
of39.588 grams of silver iodide.

Precipitation was agam somewhat below normal in most areas of western Colorado
during the 2003-2004 winter season. totaling about 80-100% of the nomlal amount across the
Gunnison County seeding target area. As of April IS. Gunnison Basin SNOTEL sites averaged
91 % of the normal water year precipitation, and only 78% of average snow water content. The
low snow \\'ater content was largely a result of warm weather in March that led to substantial
melting. The higher precipitation and snowpack amounts were generally in the southern portion
of (he basin. particularly in the vicinity of the San Juan Range. where precipitation over the
season was close to normal.

Evaluations of the potential effects of the seeding project on target area precipitation
were conducted utilizing the historical target/control approach. These evaluations considered
two types of data: precipitation observations and sno\\' water content observations. Sources of

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