WMOD00593

• Contract/Permit #: 14-06-D-7052
• Title: Ecological Impacts of Snowpack Augmentation in the San Juan Mountains, Colorado
• Date: 3/1/1976
• State: CO
• Weather Modification - Doc Type: Report

PREFACE

Cloud seeding, a widely discussed technological development of the second
half of the Twentieth Century, has many facets. One of the more promising
is winter cloud seeding aimed at augmentation of snowpack in mountainous
areas by artificial injection of ice-nucleating particles into approaching
storm clouds. The upper Colorado Basin, containing many high ranges of
the Rocky Mountains along the Continental Divide, has been recognized for
some time as a highly suitable locality for winter cloud seeding technologi-
cal and scientific investigation. It is the more appropriate because one of
the longer-term objectives is to find the means of increasing water quantity
and quality within the entire Colorado River drainage.

With the advances in cloud seeding technology through the 1960's and the
accompanying increase in understanding of cloud physics, the San Juan
Mountains of southwestern Colorado were selected as an excellent area for
large-scale scientific design to test the efficacy of winter cloud seeding.
Thus in 1968 the Division of Atmospheric Water Resources Management of the
Bureau of Reclamation began design work on the Colorado Basin Pilot Project
with its' experimental "target area" located in the San Juan Mountains.

Concurr~nt with these technological developments, the Bureau became concerned
with the'ir environmental, social, economic, and legal implications. Surveys
of the l'iterature on environmental implications beginning in 1964 showed
that there was little firm knowledge then available and that speculation
was only occasionally based upon fact. By 1968 it had become apparent,
however, that the environmental implications should be considered. Thus
the Bureau contracted with the University of Michigan for a detailed assess-
ment by Charles F. Cooper and William C. Jolly entitled "Ecological Effects
of Weath,er Modification: A Problem Analysis."

In September, 1970, the Bureau awarded a $1,014,000 contract to Colorado
State Un:iversity for the San Juan Ecology Project, the subject of this study,
to be conducted in cooperation with the Institute of Arctic and Alpine
Research of the University of Colorado, and Fort Lewis College, situated
at Durango, virtually within the study area.

When the San Juan Ecology Project was being planned it was anticipated that
artificially-induced snowfall increases could reach as high as 30 percent
above natural amounts. More recently, however, a study of potential in-
creases in precipitation in twelve western river basins, carried out by North
American, Weather Consultants, found that an effective technology in the
San Juan' study area was not likely to produce average annual increases
exceeding 10.6 percent of the natural amount. These findings, l~wever, do
not materially affect the course and outcome of the ecology project. The
higher f:Lgure of 30 percent, assumed possible at the outset, provides a
useful upper limit. Also, it had been decided originally that the ecological
research would not attempt to monitor the effects of actual artificial
increases because a 4 year project (to become 5 years) would not be nearly
of sufficient length for detection of any environmental impacts, even if
they should occur in a highly varied complex of mountain environments
characterized by great natural variation in annual snowfall. The emphasis
was placed upon study of snow-related processes ~~. Thus two primary
study areas were developed: analyses of relationships between snow and
various components of the San Juan forest ecosystems; in particular,
forest phenology, phytosociology, tree biomass and moisture stress, elk,
and small mammals; and a comparable set of analyses of alpine ecosystem
components, including tundra primary productivity, phytosociology and
phenology, decomposition, geomorphic processes, small mammals, and boreal
toad. To these were added vegetation and geomorphic mapping of the San Juan
mount,ain area and investigation of the disposition and environmE,ntal effects
of silver iodide, the cloud seeding agent used in the Colorado River Basin
Project. Paleoecology studies were included in an attempt to determine
natural environmental fluctuations through time.

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