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FINAL OPERATIONAL SEEDING SUMMARY REPORT FOR SAN JUAN MOUNTAINS WEATHER MODIFICATION PROGRAM Application for renewal of the seeding permit Western Weather Consultants, Inc. had obtained for a winter seeding program designed for the San Juan Mountains was submitted on August 22, 1980. The seeding area for the 1980-81 permit area was reduced in size by leaving out the portion of the San Juan Mountains east of the pine River Drainage. This matter was reviewed at a public meeting held on October 16, 1980, before Monte Pascoe, Executive Director, Colorado Department of Natural Resources, at the La Plata County Courthouse, Durango, Colorado. A permit to operate the program was received on October 29, 1980. The requested start-up date of operations was delayed from Novem- ber 15, 1980 to December 1, 1980. Lower snow pack cut-off sus- pension criteria and restrictions to using generators directly upwind of Silverton, Colorado, were again imposed in this season's permit. The program was operationally ready by December 1, 1980, with 13 ground-based cloud nuclei generators in place to seed the mountain barriers in the program area. All of the generators were manually operated and utilized silver iodide as the nucleating agent. Because of the unusually dry weather conditions experienced across Colorado this winter, the program sponsors requested that the seeding permit period be extended from February 15, 1981 to March 31, 1981. This requested program extension was granted by the Department of Natural Resources in February, 1981. The first treatable weather system moved across the area on Decem- ber 5, 1980. During the period of December 1, 1980 through March 31, 1981, seeding operations were conducted on all or portions of 27 calendar days out of the total 121 day operational period. These 27 days were included in 15 separate seeding operations. Total operations for the program amounted to 1,876.25 hours of generator seeding time, which dispensed 18,150.0 grams of silver iodide. Upon the completion of the seeding program, snow pack water con- tents ranged from 68% of the April 1 means in Wolf Creek Pass area, to 53% in the seeded Animas drainage, to 68% in the seeded Dolores drainage. A presentation of precipitation events to seeding events is pro- vided for informational purposes with accompanying changes in monthly snowcourse measurements. No quantitive statistical eval- uation of the seeding effects from this program will be attempted.