|
<br />PROJECT SKYWATER
<br />By ARCHIE M. KAHAN, ~hief Engineer
<br />Office of Atmospheric Wat~r Resources
<br />U. S. Bureau of Reclamation, [)enver. Colorado
<br />
<br />1. INTRODUCTION
<br />
<br />
<br />Most of you have already been exposed to a great deal of talk about weather modification,
<br />Many of you have seen, at a previous meeting of this ass9ciation, "Rivers in the Sky", the motion pic-
<br />ture that describes how and why the Bureau of Reclamation undertook its comprehensive program of
<br />research aimed at learning how better to tap the water re$ources of the atmosphere. There is, therefore
<br />probably very little need to spend time today laying the background for the now widely accepted con-
<br />cept that, under some meteorological circumstances, m~n can change the amount and/or location of
<br />precipitation. Few knowledgeable people today would :differ with the assertion that delivery of the
<br />right kind and the right amount of cloud seeding chemiQals to the right place in the atmosphere at the
<br />right time will result in changes in the behavior of the seeded clouds and in the resulting precipitation.
<br />
<br />This unanimity turns out to be somewhat fragile, however, when one attempts to find accept-
<br />ably precise definitions of what constitutes this right kind, amount, place, and time to produce desire-
<br />able changes. A host of important questions remains to be answered before anything approaching a
<br />consensus on what is "right" is reached, Between recognition of the exciting scientific fact that pre-
<br />cipitation can sometimes be artificially changed and the: existence of a widely applicable, reliable tech-
<br />nology for accomplishing such changes in an economic~lly sound and socially acceptable manner, lies
<br />a considerable gap in available knowledge. This gap is being narrowed. It is my purpose today to bring
<br />you up to date on the effort that has been mounted, mention something of what has been recently
<br />learned, and tell you what is being planned for the near future toward further narrowing of the know-
<br />ledge gap with some special emphasis in the Colorado River Basin.
<br />
<br />II. CURRENT PROJECT SKYWATER EFFORT
<br />
<br />In the current fiscal year, approximately $4,700,000 will be expended by Project Skywater in
<br />pursuance of its goal of acquiring the technology for adejing to the useful water supply, The effort sup-
<br />ported by this expenditure now extends across the nation. In response to the increasing recognition
<br />that water supply problems are not the exclusive property of the West, from the States of Washington
<br />to Florida, from California to the New England States, the best available minds have been put to work
<br />on problems of precipitation management. We have under contract 37 research groups drawn from
<br />private industry, universities, state governments, and Federal agencies. Figure I lists these groups and
<br />the II categories of effort which they are currently pursuing. Each group is playing a role contribu-
<br />tary to the eventual development of operational systems, When developed, these operating systems will
<br />include the basis for making sound decisions about wh~ther or not to apply cloud seeding technology
<br />the means of recognizing seeding opportunities, the means of proper treatment, and the basis for eval-
<br />uation of accomplishment,
<br />
<br />III. WHAT HAS BEEN LEARNED RECENTL Yi
<br />
<br />The results of several carefully designed, randoinized experiments have been published in the
<br />last 2 or 3 years, In this country and abroad, from programs sponsored by the Bureau of Reclamation
<br />and by others, a picture is emerging which shows that,cloud seeding can produce results ranging from
<br />significant increases in precipitation, through no detectable effect to actual decreases, Which of these
<br />occur appears to depend quite heavily on the temperatlire and wind structure of the atmosphere at the
<br />time of seeding, the type of storm seeded and manner ill which the seeding is carried out,
<br />
<br />Of special pertinence to the Colorado River Basin are the recently published results of an ex-
<br />cellent experiment near Climax, Colorado, conducted by Professors Lewis 0, Grant and Paul Mielke of
<br />Colorado State University under sponsorship of the National Science Foundation, Grant and Mielke
<br />analyzed 283 cases occurring from the winter of 195f)-1960 through the spring of 1965. They found
<br />that the increase in snowfall of seeded clouds over uns~eded ones averaged 54,5 percent for those cases
<br />where the 500 millibar surface temperatures (cloud top approximately) ranged between -12 and -20
<br />degrees centigrade, The amount of increase dropped to 12.3 percent for temperatures between -21 C
<br />and -23 C, A decrease of -14.8 percent resulted when, temperatures fell between -24 C and -39 C. The
<br />warmer cases were associated with a deficit of ice nuclei, while the cold cases had plenty from natural
<br />sources.
<br />
<br />j
<br />.j
<br />
<br />-34- i
<br />
|