WMOD00532

• Title: The Rain Stimulation Campaign in Panama Summer 1983
• Date: 6/1/1984
• Weather Modification - Doc Type: Report

The Rclin Stimulation
Campilign ill Panama
SUlnmer'1983

1. Executive Sunlmar~l

The Panama Canal Commission and the Instituto de
Recursos Hidraulicos y Electrificacion both faced an
emergency water supply situation in the late winter of
1983. Protracted severe drought had dropped the
water level in the Canal so low that the draft of vessels
passing through the canal had to be restricted, causing
loss of toll revenue and possible loss of future custom.
Water in the electric utility's main hydroelectric reser-
voir was so low that brownouts had to be instituted.

In late April 1983, the Commission requested technical
assistance for an emergency rain stimulation program
from the U.S. Department of the Interior, Bureau of
Reclamation, which had conducted applied research in
this field for almost 20 years. A weather-modification
scientist dispatched from Denver, Colorado" briefed
the Commission and other concerned parties on the
state of the art and the probable uncertaintie:s, risks,
and benefits involved. The Commission and the Insti-
tuto decided to proceed and the necessary permissions
from the Republic of Panama were quickly obtained.
Under an interagency agreement and transfer of funds,
the Bureau undertook to contract with a commercial
cloud-seeding company and to perform technical super-
vision of a 90-day cloud-seeding operation over the
watersheds of Lakes Gatun, Madden, and Bayano. The
sum of $325,000 was obligated for this purpose, of
which the Commission furnished $300,000 and the
Instituto $25,000.

Two aircraft, equipped for cloud seeding, were dis"
patched to Panama, arriving on May 29, 1983. One was
equipped with specialized cloud-physics instrumenta-
tion and made observations of cloud droplets, precipi-
tation particles, and other properties within natural and
seeded clouds. The contractor also sent an experienced
meteorologist to direct operations on-site, as well as
cloud-seeding pilots and other support personnel.

Cloud seeding operations began May 31 and ended
August 27,1983. Missions were flown on 61 days. On 33
of these days, both target areas were seeded; only the
Gatun/Madden targ:et on 22 days, and only the Bayano
target on 6 days. A total of 109 seeding and observation
flights with a total duration of 283 hours were
conducted.

Because of the brevity of the operation, no scientific
evaluation of the outcome was planned or performed.
Several seasons of randomized operation are usually
mquired for sound statistical evaluations. However, an
assessment of the observations made during the project
rE~sulted in the following conclusions:

. The amount of rainfall per "rainy day" was slightly
increased over the average of the previous 11
years, contributing an estimated 4 inches to the
level of Gatun Lake;

. Visual and radar observations of seeded clouds
identified what were described as "good" responses
on 9 days, with "fair" responses on another 20
days.

· The indications of positive results, though weak,
were consistent with one another and with expecta-
tions based on scientific principles.

Noting that a drought severe as that of 1983, though
rare, must be expected to recur sometime, the Bureau
recommended to the Commission the preparation of
an objective set of criteria and an early-warning system
capable of alerting the Commission to the approach of
se:vere drought conditions. Accumulation of precipi-
tation data, from a nearby area, that might be used as a

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