WMOD00413

• Title: Validation of Precipitation Management by Seeding Winter Orographic Clouds in the Colorado River Basin
• Date: 9/1/1993
• Weather Modification - Doc Type: Report

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1. INTRODUCTION

This section discusses the need for additional water in the Colorado River Basin, weather
modification as a viable alternative for enhancing water supplies, the purpose and overview of
the proposed research program, and Reclamation (Bureau of Reclamation) authority for
pursuing weather modification investigations..

1.1 Need for Additional Water

Data compiled by the GS (Geological Survey) shows that between 1985 and 1990, per capita
water consumption in the seven states which rely on the Colorado River, as measured by total
withdrawals for public supply, increased by 3 percent. This finding is especially significant in
light of the extensive water conservation efforts undertaken by urban water suppliers and
recent severe water shortages in the West. Although the wise use of our water resources is an
important national issue, it is vitally important in the arid West served by Reclamation. A 1989
report by the Bureau of the Census projected that by the year 2010, one-third of all Americans
will live in the 17 States west of the Mississippi River, the region served by Reclamation.

The staff of the House Appropriations Committee recently stated that "water is the most
serious, long range problem now confronting the nation-potentially more serious than the
energy crisis." This Nation must become wiser and better at water resources management to
meet future water needs. Conservation must be a part of our response to water shortages. But
conservation alone will not meet all our needs. It is unlikely, for example to solve watE!r quality
problems.

The Western States have been experiencing yet another dry period, which continued fbr 6 yr in
some regions. Frequent storm passages during the 1992-93 winter have eased or ended drought
conditions in some areas, but other areas will require a number of years with above! average
precipitation to fully return to normal.

Periodic droughts are to be expected in the West. Pronounced natural climatic changes have
been postulated by reconstruction of droughts in the Southwest over the past 450 yr. Tree rings
and other data have suggested past droughts which were longer and more severe than any
experienced this century. The need for new water supplies will be particularly acute if climatic
change associated with the greenhouse effect results in a drier West as predicted by some
numerical climate models.

Increased population will further strain already limited water supplies. In both the States of
California and Nevada, water agencies serving urban residents are seeking ways of further
managing water supplies to reduce the likelihood and magnitude of projected water shortages.
Both the Las Vegas Valley and the southern California coastal region rely on Colorado River
water to meet a portion of their need for water. With the commencement of the operation of
Reclamation's Central Arizona Project in 1985, the southern California coastal region lost the
dependability associated with over half of its Colorado River supply. As the population of the
Las V egas Valley continues to increase, it is forecast that this region will fall short of water
within the next two decades. Because Federal law requires that diversions of Colorado River
water to central Arizona be reduced first in the future in a time of shortage of Colorado River
water, reducing the risks of such shortages is of interest to this region. Therefore, all reasonable