Variations in Rainfall and Insured Crop-Hail Losses Associated with Operational Cloud Seeding in South Dakota

A brief review of operational cloud seeding programs in South Dakota is given, followed by an evaluation on the basis of rainfalldata and insured crop-hail loss data for the years 1948-1978. All of the projects used silver iodide as the seeding agent, but a wide variety of generator types, seeding rates, and delivery methods was used. In years w.ith aircraft seeding over small areas, both rainfall and hail damage tended to be larger in target than in non-target counties. The data available do not show such a trend for years when ground-based generators were employed. In years when 40%or more of the state was seeded, the results for target and non-target counties becameindistinguishable in terms of both rainfall and crop hail damage. However, increases in the area included in cloud seeding programs, using either ground based or airborne generators, were associated with an apparent net hail suppression effect, extending over the entire state. The rainfall data do not display such a trend.