Evaluation of cloud seeding efforts in the southern Oregon Cascades, 1952-1957

Cloud seeding operations for The California Oregon Power company have been conducted by North American Weather Consultants for the past 7 years in the Southern Oregon Cascades. The purpose was to increase the mountain snowfall and consequently, the summer streamflow for the production of hydroelectric power. The seeding methods and the climate of the areas are discussed. Based on regression and isopercentile analyses of the data for the first 6 years of seeding, the following conclusions were reached. (1) the average April 1 snow water content for 1952-1957 showed a 3% increase over the expected amount. (2) The average November-March precipitation for the 6 seeding years showed a 2% increase over the expected amount, a nonsignificant increase. (3) The average April-July streamflow for 1952-57 was 4% higher than expected, a nonsignificant increase. (4) for 4 of the 6 seeded years, the highest percent of normal precipitation in the State has occurred in the Fremont-Paisley area, lending strong support to the thesis that a downwind effect exists beyond the target area.