Abstract

Water is one of the most basic commodities on earth sustaining human life. In many regions of the world, traditional sources and supplies of ground water, rivers and reservoirs, are either inadequate or under threat from ever-increasing demands on water from changes in land use and growing populations. Only a small part of the available moisture in clouds is transformed into precipitation that reaches the surface. This has prompted scientists and engineers to explore the possibility of augmenting water supplies by means of cloud seeding. Cloud seeding is a form of weather modification, a way of changing the amount or type of precipitation that falls from clouds, by dispersing substances into the air that serve as cloud condensation or ice nuclei, which alter the microphysical processes within the cloud. The most common chemicals used for cloud seeding include silver iodide, potassium iodide and dry ice. Liquid propane, which expands into a gas, has also been used. Cloud seeding is done to enhance the amount of precipitation that falls in a region, disperses fog and clouds so that a place can remain dry through precipitation, minimize the sum of cloud cover, purify the air of pollutants, and assist in extinguishing wildfires through rain.