Use of snow surveys in evaluating cloud-seeding operations

Methods using data from mountain snow survey courses to study the results of cloud seeding are presented. Cloud seeding, to increase the snowpack and produce more water for irrigation on watersheds of the Rogue River Valley, Oregon, occurred from November 1949 through March 1950, and from November 1950 through March 1951. The target area and the techniques used in cloud seeding are described. Snow course records maintained 9-19 years in the target area and in upwind surrounding areas were analyzed. Correlation coefficients were established and used to determine if the target area received proportionately more or less water equivalent as snow than the surrounding areas. Analysis shows that less water was stored in the snow in the target area during the 2-year period of cloud seeding than expected under natural conditions. Further studies are required to determine whether the relationships between snow courses and streamflow sere modified by seeding.