WMOD00415

• Title: Winter Cloud Seeding Potential on the Mogollon Rim - Final Report
• Date: 1/1/1989
• Weather Modification - Doc Type: Report

1. INTRODUCTION

1.1 General

This report discusses the collection and analyses of meteorological data obtained by the Bureau of
Reclamation during the first two exploratory observational programs for the ASAP (Arizona Snowpack
Augmentation Program). Field observations were made in the Mogollon Rim area of Arizona during the
periods of January 14 through March 17, 1987, and January 15 through March 10, 1988. The work was
conducted as part of a cooperative effort with the Arizona DWR (Department of Water Resources). The
primary objective was to examine the water supply augmentation potential of winter storms for possible
future application of weather modification (cloud seeding) technology. This was accomplished by
investigating natural storms and precipitation processes. No cloud seeding was conducted during either the
1987 or 1988 studies.

1.2 Background

The Arizona DWR has a statutory requirement to include water augmentation alternatives in water
management planning. One potential alternative considered by DWR is the possibility of applying cloud
seeding technology to enhance winter precipitation on the higher elevations of the Mogollon Rim. Although
not currently quantifiable in Arizona, increased winter snowfalls are expected to translate into additional
water available to augment both instream flows and aquifer recharge.

The DWR initiated discussions with Reclamation's Water Augmentation Group (previously the Division of
Atmospheric Resources Research), which directs Project Skywater--a Federal program that conducts applied
cloud seeding research and development studies and assists in technology transfers to interested users. The
initial discussions culminated with the fmalization of an Intergovernmental Agreement between the State of
Arizona and the Bureau of Reclamation. This agreement provided funds to Reclamation to conduct a
feasibility study using historical climatological data. The final report for this work (Reclamation, 1987a)
identified major precipitation storm-producing patterns; considered these patterns for wet, normal, and dry
years; and made estimates of their augmentation potential using model studies and results from past winter
programs. It was concluded that moderate potential for snowfall augmentation probably exists, at least for
some storm situations.

While the climatological study was being conducted, DWR was encouraged by a broad-based group of
Arizona water entities to actively pursue initiation of a long-range cloud seeding demonstration program.
Reclamation was asked to assist DWR in developing alternatives. It was mutually concluded that further
assessment of the augmentation potential of Arizona winter storms, based on in situ field measurements,
should be performed prior to initiating a long-term effort. In early 1987, Reclamation and DWR reached an
arrangement to conduct an initial 2-month intensive observational program over the Mogollon Rim.

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