WMOD00382

• Project Name: Project Skywater
• Title: Project Skywater - Water Augmentation through Cloud Seeding
• Date: 7/1/1989
• Weather Modification - Doc Type: Report

From a rigorous scientific standpoint, the results of cloud seeding projects cannot be
determined with absolute certainty. However, despite residual uncertainties in the evidence for
precipitation enhancement, the conclusions reached over two decades ago that certain kinds of
precipitation can be increased by 10 percent or more have been generally supported. Based
on current scientific knowledge, the best that can be done is to find situations where cloud
seeding is within risk levels acceptable to the user. Some techniques that satisfy this criteria
are now available for use, and more can be expected as the science of weather modification
progresses. The large number of operational programs conducted in the United States and in
foreign countries each year shows that, in the opinion of many water project managers, the
risks and costs of cloud seeding are small in comparison to the benefits that might be gained.

The philosophy of the Skywater managers is to assess the scientific and socioeconomic
feasibility of existing precipitation enhancement technologies as a water resource tool even
while seeking to improve them and, where appropriate, to provide demonstrations of their
effectiveness. In a few cases, Reclamation has provided technical assistance and advice to
groups involved in applied cloud seeding projects, often of an emergency drought relief nature.

Reclamation's approach has been to employ two methods to even out variations or ease
shortages in water supplies by augmenting precipitation through cloud seeding. The first is
to increase the amount of water stored in reservoirs, which is then available to draw upon
when and where needed. This method often involves seeding orographic clouds to increase
snowpack and subsequent runoff in mountainous areas. However, there are many situations
where this method is not feasible and seeding to produce water for direct application is the
only practical method. This second method often involves seeding convective clouds to
increase rainfall for immediate use on croplands and rangelands when it is needed during the
growing season.

Regardless of which of these two methods is involved, a program of precipitation enhancement
is most effective if it is used on a long-term basis in the context of a total water management
program. Seeding should be used to increase precipitation whenever seeding opportunities
arise and the hydrologic situation warrants, to build soil moisture, to improve the condition
of the cropland and rangeland, and to increase stored water supplies. The technology needs
to be applied before a drought develops, when opportunities are more plentiful, to cushion the
impact of the drought.

In some situations emergency measures are necessary even though the deficiencies resulting
from a drought, which may have taken years to develop, cannot be quickly replenished by last
minute emergency cloud seeding efforts. The moderate amount of additional precipitation
produced by cloud seeding will not provide total relief from a drought, but it will help,
especially if it occurs at crucial times in crop growth and in crucial locales for reservoir
storage.

The Skywater approach to cloud seeding emphasizes assessing the ecological, economic and
social impacts of cloud seeding, and the minimizing the risks in both experiments and applied
projects. Research has indicated that neither the added precipitation nor the seeding agent
adversely affect the ecology of areas as a result of short-term research or demonstration cloud
seeding programs. Continued environmental monitoring is needed to clarify the validity and

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