WMOD00592

• Project Name: Project Skywater
• Title: Project Skywater - Final Environmental Statement - Volume I
• Date: 1/1/1977
• Weather Modification - Doc Type: Report

(4) study of relationships between cloud seeding and ava-
lanches. A fifth project analyzed the data and evaluated
the results of seeding on precipitation and streamflow.

~~ch of the 3,370-square-kilometer (1,300-rni2) study area
was above 2,75U meters (9000 it) in elevation, where,
except on some south-facing slopes, snow usually covers
the groWld aU winter. After several years of planning
and preparation, seeding began in the autumn of 1970. The
project design defined a seedable event as a day during
some determinate part of which the wind, temperature and
humidity aloft, and expectation of snowfall all fell within
specified linits established from a physical hypothesis of
the snow-stimulation process. A total of 147 experimental
events, randomly divided into seeded and unseeded classes,
constitutes the body of experimental data.

The seeding project released a total of 319.629 kilograms
(704.66 Ib) of silver iodide from the groWld during the
five winter seasons. At maximum output, downwind concen-
trations of silver iodide are computed to be about 5 x 10-8
grams per cubic meter or less at a distance of 100 meters.
5 x 10-10 grams per cubic meter at 1 kilometer, and 5 x 10-11
grams per cubic meter at 10 kilometers from a generator and
along the centerline of the plume (fig. 1-9). Surface con-
centrations were normally less than these values. Under some
meteorological conditions, a portion of the silver iodide
remained in the lower hWldred yards of the atmosphere for a
number of hours and spread over considerable distances before
being carried aloft.

Operation of the project required visits to instrumentation
and equipment sites. Some of the instrumentation and equip-
ment was removed in the spring and reinstalled in the fall,
and most sites were visited for maintenance. The vast major-
ity of these sites were located on public lands and were
accessed via existing roads, horseback or by helicopter
(fig. 1-10). Fifteen of the 35 generators were located on
private land. Most of the sites required some sort of semi-
permanent construction, such as cement pads or instrument
shelters. and some of the sites are shared with several other
agencies. Figure 1-11 shows some t}~ical site instrumentation.

The Bureau of Reclamation and its field contractors cooper-
ated on this program with a number of other agencies. The
seeding contractor complied with the State of Colorado licens-
ing requirements. The Colorado State Highway Department and

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