Winter Orographic Cloud Seeding Northeast of Bear Lake, Utah

A wintertime operational cloud seeding program was conducted in portions of the Bear Lake watershed of Utah, Wyoming, and Idaho for a 15 year period. Seeding operations were curtailed in 1970 but initiated again in 1979. This sequence of events provides the opportunity to examine possible seedinq effects over the 18 year period as well as studying the natural precipitation regime that fell between the two seeded periods. Results of this analysis indicate approximately an 11 percent increase in April I snowpack water content based upon a target/control evaluation. A double mass plot of the target/control April 1 snowpack water content indicates breaks in slope coincident with the years of project initiation, termination, and re-initiation. This double mass plot lends considerable credence to the interpretation that the indicated 11 percent difference in snowpack can be attributed to the cloud seeding activities.