| OCR Text |
Show would be distributed by the wind in the same manner as natural snowfall. Those areas normally swept free of snow by the wind will remain snow- free. Those areas which normally have snowdrifts would continue to have snowdrifts. Under seeded conditions these snowdrifts would be deeper and somewhat larger in area. Long- persisting snowbanks cover a very small fraction of the snow- accumulation zone. Additional precipitation from cloud seeding would enable these snowbanks to persist somewhat longer. Only the immediate vicinity of these snowbanks would be affected by the higher moisture content of the soil and the cooler microclimate. Studies conducted for the Bureau of Reclamation by the Rocky Mountain Forest and Range Experiment Station of the Forest Service have shown that a snowpack of 150 percent of normal would last at a given place only about 5 days longer than one which is equal to the normal. Most runoff from snowmelt becomes groundwater. Sncwmelt becomes surface runoff only when the oil under the snow is frozen and has a high water content. Since the melting zone of the snowpack remains relatively constant in thickness and only this portion contributes to runoff at any one time, the additional snowpack resulting from cloud seeding would lengthen the runoff season. Since seeding would be quite limited in years with heavy snowpack, the effects of unusually high streamflow patterns would not be particularly changed by the presence of artificially induced snow. Downwind Effects of Cloud Seeding Three long- term operational cloud- seeding projects and two long- term randomized research projects which used silver iodide to seed winter orographic storms in the western United States were investigated to see if any downwind effects of cloud seeding could be detected. Considerable statistical evidence was obtained which indicated that areas 30 to 150 miles downwind from the primary project area were receiving appreciable precipitation increases during seeding activity. The sparse precipitation- gage network used in the analysis did not warrant the application of tests of significance because of the limited number of test cases. The study did show that the phenomenon merited further investigation. 513 |
