WMOD00155

• Contract/Permit #: #94-6
• Applicant: North American Weather
• Project Name: Willow Creek Basin
• Date: 11/1/1993
• Weather Modification - Doc Type: Report

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6.0 SUMMARY AND RECOMMENDATIONS

A second winter season of cloud seeding operations was conducted over the
Willow Creek Drainage located in north central Colorado. The program was operated
during a two month period between February I, 1994 and March 31. As in the first
season, seeding was accomplished using 15 ground based silver iodide generators. There
were eight seeding episodes during the operational period in which the generators were
operated a total of 574.5 hours.

An evaluation of the second season of operations, based on a target-control
comparison of April I snowpack (water content), indicates that a possible increase of
approximately 25 percent occurred. This percentage is higher than anticipated and may
be partly due to the unusual 1993-94 winter season experienced in western Colorado.
Taken together with the results of the winter of 1992-1993 (positive 15 %) the result
indicated a possible 20 percent increase.

The operational design of the program worked well again this year. Southerly
flow was less ('ommon this year when compared to 1992-1993 and as a result the
southern most generators were operated less often this season. These sites continue to
be in a good position when winds are more southerly, as is often the case in pre-frontal
weather situations and it is recommended they should be kept in place.

NA WC will be testing different seeding solution mixtures during the winter of
1994- I 995. This testing is being conducted in the interest of developing more efficient
seeding material output. If progress is made in this endeavor, results will be released
to the NCWCD for their possible use in future projects.

It is recommended that this program be continued. An earlier start date (perhaps

in November) would insure that no good seeding opportunities are missed during a water

year that turns out to be below normal.

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