Cloud Seeding in Southern Puerto Rico, April–July 1965

Abstract

With the most severe drought on record in its eighteenth month, causing severe damage and hardship in Puerto Rico, several large private concerns and government agencies interested in water decided that the immediate need for water greatly outweighed the uncertainties involved in cloud seeding, and collaborated to sponsor a program of rainfall stimulation. Operations of an emergency nature began 26 April and continued until 18 July 1965. The result is evaluated by estimating the amount of rain that would have fallen if no seeding had been done, from the average rainfall per rainy day during a 19-year (unseeded) period. This analysis indicated an increase of 2.69 inches, equivalent to a 14 per cent increase nominally significant at the 10 per cent level. No formal evaluation of the economic outcome is offered, but crop reports suggest that the cloud-seeding program returned value many times its cost, hence justifying the undertaking in the face of the uncertainties involved.