Managing Water Resources in the West Under Conditions of Climate Uncertainty A Proceedings (1991) / Chapter Skim
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18. Weather Modification as a Response to Variations in Weather and Climate
18. Weather Modification as a Response to Variations in Weather and Climate
Pages 296-302
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From page 296... ...
The Bureau of Reclamation has been conducting research on precipitation augmentation for the past 30 years, with the efforts in recent years concentrated on the seeding of winter orographic clouds to increase snowpack and runoff. THE SEEDING OF WINTER OROGRAPHIC CLOUDS In the face of water demands that often outstrip supplies, western water managers have been using weather modification to augment water supplies each year since 1948.
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From page 297... ...
Subsequent analyses have confirmed that the economic impact of a successful weather modification program could be very large. A Bureau of Reclamation analysis of a hypothetical 10 percent increase in Colorado River streamflow showed average annual benefits of $48 million from increased water supplies for irrigation and for municipal and industrial use; $34 million from increased hydropower generation; and $62 million from improved water quality (chiefly from a reduction in salinity)
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From page 298... ...
The latest policy statement of the American Meteorological Society on weather modification states: "Precipitation amounts from certain cold orographic cloud systems apparently can be increased with existing technology in the western United States. Increases of the order of 10 percent in seasonal precipitation are indicated in some areas." It is difficult to translate indications of precipitation increases at individual gauges into estimates of additional runoff from an entire watershed.
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From page 299... ...
Projects to enhance precipitation are most likely to be undertaken following dry periods, when water supplies are low. The most favorable seeding opportunities in orographic clouds are the shallow clouds, rather than the deep clouds associated with major storms.
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From page 300... ...
Results of the various experiments and operational programs suggest that a variety of outcomes is possible and that tailoring a seeding operation to a particular project area requires careful consideration of wind fields, generator siting, seeding agent diffusion and transport, and cloud microphysical characteristics (including the presence or absence of secondary ice formation)
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From page 301... ...
Experimental confirmation for this expectation is provided by apparently successful cloud seeding projects in such arid areas as San Diego County, California and northern Israel. Radiometer data from Arizona show that seedable conditions occur several times each winter and sometimes last for 20 or 30 hours at a stretch, with only intermittent, light snow falling during that period.
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From page 302... ...
1980. Weather Modification by Cloud Seeding.
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