WSP06362

• File Number: 8210.470
• Description: Pacific Southwest Interagency Committee
• State: CO
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 11/1/1971
• Author: PSIAC
• Title: Pacific Southwest Analytical Summary Report on Water and Land Resources based on Framework Studies of Four Regions - November 1971
• Water Supply Pro - Doc Type: Report/Study

80Z668

and 7.5 million to the Lower Basin. In addition to
the apportionment in Article III( a), the Lower
Basin is given the right to increase its beneficial
consumptive use of such waters by one million
acre-feet per annum. In 1948 the Upper Basin
States - Colorado, New Mexico, Utah, and Wyoming
- apportioned the share among themselves and
Arizona (for that portion of Arizona in the Upper
Colorado Basin). The United States Supreme Court
in 1964 apportioned the mainstream water among
the States of Arizona, California, and Nevada. A
treaty between the United States and Mexico in
1944 guarantees delivery to that country of 1.5
million acre-feet annually, but with provisions for
delivery of greater or lesser amounts in certain
circumstances. Some development of water utiliza.
tion projects has been delayed as a result of this long
and involved process of negotiation and litigation.

The Colorado River Compact requires, among
other things, that "the States of the Upper Division
will not cause the flow ofthe river at Lee Ferry to be
depleted below an aggregate of 75,000,000 acre.feet
for any period of ten consecutive years. . . "; that any
water committed to Mexico "_ . . shall be supplied
first from the waters which are surplus over and
above the aggregate of the quantities.. . " (appor-
tioned to the Upper and Lower Basin); and" . _ if
such surplus shall prove insufficient for this purpose,
then, the burden of such deficiency shall be equally
borne by the Upper Basin and the Lower Basin. . . ".

While the legal conflict respecting water rights
continued, the completion of Hoover Dam in 1935 at
least brought some physical control to the Lower
Colorado River. The dam also started producing the
hydroelectric revenues necessary to pay for the dam.
Another engineering feat of that day was the con-
struction of the Colorado River Aqueduct from
Lake Havasu on the Colorado River to the metro-
politan area of southern California, a distance of
about 200 miles.

Following World War II, water development was
accelerated in the Pacific Southwest. Many projects
have been completed, many more are under construe.
tion and planned. Outstanding among these are the
Central Valley Project of California, with its extensive
conveyance and distribution facilities, and the Cali.
fornia State Water Project presently under construc-
tion. Another is the Colorado River Storage Project,

Water Resources

The Pacific Southwest has many natural resources.
Yet the use of most of these depends on just one of
them - water. And it is the major resource in short
supply. The history of development in this area
begins with water and the difficulties associated with
its use.
Although there are sharp contrasts in the water
resources of the four regions of the Pacific South-
west, the transfer of water between regions provides
an element of unity. Three of the regions are wholly
or partly within the Colorado River Basin and all four
of them depend on it for part of their supply. Also,
the Truckee, Carson, and Walker Rivers which origi-
nate in California are major sources of water supply
for the Great Basin Region.
Man had to take water far from its natural courses
to utilize or develop the West's resources. Because of
this, whole new legal and engineering approaches
were developed. The largest early diversions of
natural water were for mining and agriculture. Agri-
culture developed throughout the area wherever the
combination of arable land, water, and markets (or
transportation to markets) made it feasible.
The need for Federal involvement in water de-
velopment became apparent in the late 1800's, when
the costs and scope of additional water development
were obviously beyond the financial capabilities and
jurisdictions of private investors, development dis-
tricts or States.
As the cities grew, they too reached out farther
and farther for water supplies. When the city of Los
Angeles completed its Owens Valley Aqueduct in
1913 - bringing water from a high mountain valley
240 miles to the city's hydrants and faucets - a new
era was opened. Other cities followed the example of
the infant metropolis.
San Francisco's Hetch Hetchy project gave San
Franciscans Sierra water from the Tuolumne River
120 miles away. Similar, though smaller, diversions
were developing to supply the other cities of the
Pacific Southwest.
California's growing use of the Colorado River to
irrigate desert valleys and supply more water for a
growing population led directly to the Colorado River
Compact, drafted in 1922 and established in 1929.
The Colorado River States divided the river into two
basins, Upper and Lower.
In Article III(a), the Compact apportioned 7.5
million acre-feet per annum to the Upper Basin

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