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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Gunnison River drainage. Therefore. a total of nine target area snow water content observation
sites were available. The locations of these sites are provided in Figure -t.5.

The same set of control sites used in the 2002-03 evaluation was used in the development
of regression equations for the 2003-Q..l. winter season program. A total of live sites were used as
comTois. many the same as SXOTEL sites used in the precipitation control !,,'TOUp. Control and
target area site names. elevations and locations are provided in Tables 4-3 and 4-4. Elevations
for the control area sites averaged -9200 feet MSL. while those in the target area averaged
-9800 feet. The relationship of the control area snowpack sites to the target area is shown in
Figure 4.5. where site labels correspond to Tables 4-) and 4.4.

The linear regression equation developed for the average control snowpack data and the
average target snowpack data for April I SI water content for all target sites. including McClure
Pass. was the following:

Y c = 0.75 . Xo + 1.67

(5)

where Yc is the calculated average snow water content (inches) for the 9-station target, and Xo
is the 5-station control average observed April ISI snow water content. The r value for this
equation was 0.86. suggesting that 74% of the target/control variation is explained by the
regression equation.

Another regression equation (6) was developed for the snowpack target sites excluding
McClure Pass:

'\"c=0.71 * Xo+ 1.92

(6)

The r value for equation (6) was 0.84, suggesting that 71 % of the target/control difference is
explained by the regression equation.

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