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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Schofield Pass contained in Table 2-2 (i.e. an increase in average snow water content of
7.4" during the month of April).

2.6.3 Seedable Periods

The frequency of seedable periods during the November through April period is
expected to vary. NA WC proposes to utilize the generalized seeding criteria contained in
Table 2-5 to conduct this project. Figure 2.9 suggests that the 700 mb temperatures may
be too wann in some storm periods throughout the period (since these are average values,
but especially during the month of November. Figure 2.10 suggests that there will be
more storm periods that exhibit low-level inversion problems (which could trap the silver
iodide particles at temperatures too wann for activation) especially during the months of
November, December and January.

2.6.4 Silver Iodide Seeding Generators

NA WC proposes to conduct this winter seeding project using our manually
operated silver iodide generators. Approximately 18-20 generators will be used.
Potential locations are provided in Figure 2.11. These generators would be sited at local
residences upwind of the target areas. Desired spacing of the generators is 5-10 miles
apart based upon research conducted in Utah (Griffith, et at, 1992). Figures 2.1 through
2.7 indicate that the lower level wind flow during most of the period will be from the
southwest. As a consequence, generators should be predominately sited southwest of the
target barriers. The local residents will be trained in the operation of the generators.
They will turn the generators on or off upon receipt of instructions from NA WC
meteorologists. The generators will bum a solution of acetone, silver iodide, sodium
iodide and paradichlorobenzene. This solution has been demonstrated in the Colorado
Cloud Simulation Laboratory to produce high numbers of effective silver iodide particles
at warm temperatures that activate quickly (Finnegan, 1999). Both factors are important
in optimizing the effectiveness of this seeding project. Each generator will emit 8 grams
of silver iodide per hour of operation. Figure 2.12 provides a photograph of a typical

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