Transcript for Mountain Skywater, segment 03 of 12


Again man looks to his own efforts to increase the flow of water. Since the nineteen forty-six experiments of Doctor Vincent Schaeffer, we have known that some clouds can be modified through seeding to yield additional precipitation. But reliable seeding techniques were hard to develop. Sometimes seeding worked and sometimes it didn't.

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In nineteen sixty-one, Congress directed the Bureau of Reclamation to begin a long range study of cloud seeding with the aim of eventually augmenting the nation's supply of water. The program, called Project Skywater, continues at many sites throughout the United States. Eventually, if the research program proves successful, the methods learned will become part of our nation's integrated water resources program. Enough is now known from field experiments to conduct a pilot project where test results are applied to a more extensive area. Because the need for water is so great, the Colorado River Basin was selected for the first major pilot project.

Investigations showed that the San Juan Mountains in southwestern Colorado offer many suitable cloud seeding opportunities on clouds that form when moist air blows in from the southwest. Generators placed upwind could provide silver iodide particles that will flow with the air rising over the range. A storm with low speed winds could be seeded from generators a few miles away. High speed winds would require use of generators farther from the mountains.

Research has shown that temperature is critical. Maximum snow crystal growth occurs at minus fifteen degrees Centigrade. If the cloud is too warm or too cold, seeding is not effective. The very tiny silver iodide particles act as nuclei around which moisture from the cloud will freeze. After a silver iodide particle has been in the cloud about fifteen to thirty minutes, the snow crystal which has grown around it is large enough to begin its fall to the ground.

Scientists who designed the pilot project for the San Juans built a model and a wind tunnel to study air currents over the mountains.

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Thirty-three silver iodide generators were then installed in selected positions upwind from the one hundred mile long target area. Headquarters for the project was placed at Durango, Colorado.