WMOD00385

• Title: Augmentation Potential through Weather Modification - Working Document
• Date: 2/1/1975
• Weather Modification - Doc Type: Report

liability has not been resolved. Companies which insure cloud seeders
have little or no cloud seeding claims experience upon which to base
their premium rates.

Environmental Aspects

Precipitation management, successfully carried out on a large scale
for more than 5 years, will almost certainly have an effect on the
environment. It will tend to stabilize the precipitation - that is,
dry years will not be so dry. Such a program would favor plants and
animals adapted to a wetter environment with less variation from year
to year.

Results of studies to date suggest no substantial effects on plant and
animal communities from the changes in precipitation expected. No
adverse effects of silver iodide, in the small amount used in seeding,
have been determined. Ecologists are developing models that ~ill be
able to predict with a fair degree of accuracy the effects of prolonged
precipitation modification. When the widespread droughts of the 1930's
ended, the vegetation quickly returned to its predrought pattern. It
is reasonable, therefore, to assume that undesirable effects of precip-
itation management can be reversed simply by suspending seeding and
letting the natural precipitation regime resume. There is no evidence
that precipitation management creates irreversible effects on any
natural system (biological, atmospheric, etc.).

An ecological study in the San Juan t>lountains of southwestern Colorado,
after the third year of investigation, found no adverse effects of
additional snow on small and large mammals. Another study shows no
adverse effects of silver iodide seeding material on the mic:ro-
organisms found in the digestive tracts of rumen and nonrumen. The
interim indications from these studies are that there are no harmful
and irreversible effects.

"

Cloud seeding does not adversely affect the quality of the atmosphere.
The seeding material diffuses so quickly that it is invisible in the
air within a matter of a few hundred feet. The materials being used
are not harmful in the concentrations involved. The amount of seeding
material in the precipitation is very small. Furthermore, not all of
the precipitation for a season will be the result of seeding, so the
water on the ground or in the streams or tied up as snowpack is further
diluting the seeded precipitation.

,

The effects of increased precipitation on flooding and avalanche
occurrence have been considered. Although the amount of snow is but
one of the many factors influencing avalanches, a study is underway

11