Document Type

Report

Publication Date

1-1-1979

Abstract

  1. Operation Framework

In the arid climate of Southern and Central Utah, there is a continuing need to augment water supplies. While much of the water is needed for summertime use, particularly for irrigation, most of the available water is supplied by winter storms. Therefore, it is for the augmentation of the water stored naturally as snowpack at higher elevations that cloud seeding can make its greatest contribution.

Over the past several years, an attempt has been made to augment the snowpack by cloud seeding. Although there is a physical basis for expecting an increase in precipitation from a scientifically managed cloud seeding program, the empirical evidence that such increases have actually resulted is inconclusive. If the desired increases have not been achieved, the most likely explanation is that the empirical data necessary to distinguish seeding opportunities adequately have not been collected and applied. Presently, it is worthwhile to design a cloud seeding program in which plans are made beforehand to obtain appropriate field data for use in the execution and evaluation of the program.

Inasmuch as both the clouds available for seeding and the precipitation and storage of water in the form of snowpack are concentrated in the mountains, the area of precipitation augmentation is best confined also to the mountains. Even though the duration of the seeding program may be indefinite, the duration of operation to be evaluated should be defined in advance and carried out as planned. To do otherwise could introduce unwanted bias and doubtful conclusions.

Although an improved operational project with an extensive evaluation included in the design costs much more than that of a simple cloud seeding effort, the benefits will undoubtedly justify the expenditure. The reason is twofold. In terms of immediate benefits, the program will improve determination of which clouds or storms are seedable and concentrate the seeding effort where it will be most beneficial. In the long run, a properly planned and executed evaluation will produce results that will enhance the long term stability of the seeding program as a while.

Concerning the socio-economic impact of more effective cloud seeding, the benefits of an increased snowpack are likely to far exceed both the cost of benefits of an increased snowpack are likely to far exceed both the cost of the program and any occasional undesirable side effects. However, the disbenefits of the program should not be overlooked. Potential problems include increased flooding during spring runoff, increased avalanche hazard, and increased inconvenience to mountain communities. On the other hand, only artificial increases of precipitation in these occurrences can reasonably be attributed to cloud seeding. Therefore, it is worthwhile to include in the plan sufficient measurements that can be used to deal with such problems on a rational basis. Finally, a public education effort should be included so that information on all aspects of the cloud seeding program and its reason for being are available to the public.

  1. Research Framework

The research associated with this program should be primarily directed toward achieving a definitive evaluation of seeding effects. To accomplish this goal, the evaluation must be specifically designed to do so. Therefore, there are two requirements placed upon the total program, one is to increase precipitation, the other is to clearly demonstrate that precipitation has indeed been increased.

A secondary objective of the research is to develop a knowledge of the actual potential for increased precipitation in the target area. Measurements of relevant parameters over space and time are needed to determine the spatial and temporal variability as well as the frequency of seedable storms. At the same time, the vertical temperature stability at low levels is needed to determine the fraction of time ground seeding generators are effective. In order to increase precipitation efficiently, these measurements are needed anyway. The only extra work needed to improve our knowledge of seeding potential is an analysis of such data as it becomes available.

Research to develop improved methods of indentifying seedability, determine what type of seeding material to use, or decide whether it is better to seed by air or ground requires systematic data collection, but the effort needs to be much more concentrated than appropriate for the general clouding seeding operation and evaluation described here. Such research data collection and evaluation are best left to controlled experiments such as are being conducted at Utah State University.

The present project should, in contrast, emphasize measurements needed in the application of previous research results and evaluation of what is actually achieved by cloud seeding in an operational mode. The technology employed should not include promising methods or approaches still being studied but not yet tested in confirmatory experiments.