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

0023'0

Other Sources of Water

Weather Modification. - Increases of precipitation
induced by cloud.seeding techniques have been
demonstrated by a large number of experiments.
However, much remains to be learned about the
physical processes involved as well as resolution of
legal and social problems. Because of the climatic
regime in the Pacific Southwest, the principal result
of a successful cloud-seeding program would be an
increase of the snowpack in the mountains. The areas
most physically suitable for such a program include
the Sierra Nevada and the Transverse Ranges in
California, the Wasatch Range in Utah, and
mountains in the headwater areas of the Colorado
River and the Gila River in Arizona and New Mexico.
Desalting. - In the effort to produce fresh water
from the ocean or brackish sources, two major types
of process have been developed - distillation and
membrane processes. Distillation has been the com-
monest process for use with sea water or other source
with more than 5,000 milligrams per liter (mg/I) of
dissolved solids. The membrane processes have been
used mostly for fresher water sources (1,500 to 5,000
mg/I). Distillation produces water with extremely low
concentrations of dissolved solids (5-25 mg/I);mem-
brane processes generally produce water of good
quality but with higher concentrations (100-500
mg/I). The distilled water is especially valuable where
the chemical quality of natural supplies is poor be-
cause distilled water can be mixed with the natural
supply to improve quality as well as augment the
quantity.
The production of large amounts of fresh water
from the ocean might have significant effects far
beyond the area in which the water would be used.
For example, if desalted sea water should replace
Colorado River water in parts of southern California,
the river water would be available for use in other
parts of the Colorado River service area (assuming
that arrangements concerning water rights and costs
could be worked out).
Sources of water for desalting, in addition to the
Pacific Ocean and the Gulf of California, include
saline springs or groundwater, return flows from
irrigated tracts, and waste water from municipalities
and industry. In a closed basin, such water may be
the principal inflow to a terminal lake, and the
decision on desalting would involve the future regi-
men of the lake.
Desalting is one of several possibilities for con-
trolling the future regimen of the Salton Sea in
California. If the sea's fishery is to be preserved in
approximately its present condition, a relatively small
amount of salt must be removed each year to pre-
vent further increases in salinity.
In all desalting concepts the disposal of the salt

Water Resources

residue poses an environmental problem of varying
magnitude.
Geothermal. - Recent investigations indicate sub-
stantial quantities of hot saline water underlie the
Imperial Valley. The quantity of water has been
estimated to be as much as 3 billion acre-feet, most of
which is at depths of 5,000 feet or more. Interest in
the development of both power and distilled water
from this resource is considerable, but many prob-
lems (especially those relating to land subsidence and
disposal of brine) remain to be solved before the
large-scale development can proceed. The information
now available is not sufficient for a reliable appraisal
of the magnitude or usefulness of this potential
source of water and power.

Development to 1965

The degree of water resources development is
indicated both by the depletion of the natural supply
and by the amount of storage available for regulation
of the supply. A factor that is particularly significant
in the Pacific Southwest is the need to transfer water
over great distances.
To regulate the Pacific Southwest's water supply
and control floods, by 1965 about 96 million
acre-feet of storage capacity had been provided. A
large part of this total is for regulation of the
Colorado River and incidental production of hydro.
electric power and other purposes. The usable storage
capacity available for regulation of the flow at Lee
Ferry is about 25 million acre-feet; a capacity of 29
million is available in main stem reservoirs below Lee
Ferry. Most of the perennial streams in arid or
semiarid areas are almost completely regulated; but
some additional storage is needed to make water
available at certain headwater sites.
Amounts of the remaining unregulated and unused
streamflow are relatively small. Most of the un-
developed streamflow is in the north coastal area of
the California Region. In the Upper Colorado Region
only a portion of the remaining flow is available for
additional development in that region, because this
flow also supplies parts of the California and Lower
Colorado Regions and Mexico. Current usage and
initial filling of newly constructed Upper Basin
reservoirs account for the nearly complete utilization
of Colorado River flows.
The amounts of water used may be indicated in
terms of water withdrawn from the various sources or
in terms of the amount by which the use depletes the
available supply_ As water returned to a source
commonly is reused, the depletions are significant.
Some of the depletion is reflected in a reduction of
streamflow, some in a reduction of groundwater in
storage.
The total depletions resulting from the use of

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