WSP06497

• File Number: 8270.100
• Description: Colorado River Basin Water Quality/Salinity -- Misc Water Quality
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 1/1/1974
• Author: USDOI
• Title: Colorado River Water Quality Improvement Program - Status Report
• Water Supply Pro - Doc Type: Report/Study

industrial water users. Damage estimates have been
examined by EPA, by a trio of Colorado State
University professors, by Dr. Po-Chuan Sun of the
University of California, and by other researchers. The
reclamation water quality improvement program staff
is interpreting and adding to this work. A summary
description of the work accomplished to date follows.
It must be emphasized that final, conclusive
determinations have not yet been made on this subject.

DISCUSSION OF ECONOMIC IMPACT
OF SALINITY

As salinity levels rise, the net economic return from
agriculture decreases to SOITl€ extent. Municipal and
industrial water users also may incur additional costs of
an uncertain magnitude.

As an indication of the magnitude of salinity damages,
the EPA estimated (for 1970) total annual economic
detriments to be $16 million. If water resource
development proceeds as proposed and no salinity
controls are implemented, it is estimated that the
detriments would increase to $28 million in 1980 and
$51 million in 2010. If future water resource
development is limited to those projects under
construction, estimated annual detriments would
increase to $21 million in 1980 and $29 million in
2010. Detriments to recreation and fishery users in the
Salton Sea are not included in these EPA estimates but
are believed to be substantial. Other studies indicate
that these values were extremely low and considerable
effort has been expended to update and improve the
estimates.

The impacts of changing salinity may include effects
on fish and wildlife, recreation, environmental, and
others. While recognizing that many other effects of
salinity changes exist, the overriding concern addressed
here deals with the effects upon direct users of
Colorado River water.

Salinity effects on agricultural uses are manifested
primarily by limitations on the types of crops that may
be irrigated with a given water supply and by
reductions of crop yields as salinity levels increase.
Other conditions being equal, as salinity levels increase
in applied irrigation water, salinity levels in the root
zone of the soil also increase.

Because different crops have different tolerances to
salts in the root zone, limits are placed on the types of
crops that may be grown. When salinity levels in the
soil increase above the threshold levels of a crop,

progressive impairment of the crop growth and yield
results. I rrigation water which has a high percentage of
sodium ions may also affect soil structure and cause
adverse effects on crop production.

Domestic uses comprise the major utilization of
municipal water suppl ies. Total hardness, a parameter
closely related to sal inity, is of considerable interest in
assessing water quality effects on these uses. Increases
in the concentration of salinity and hardness lead to
added soap and detergent consumption, corrosion, and
scaling of metal water pipes and water heaters,
accelerated fabric wear, added water softening costs,
and in extreme cases, abandonment of a supply. By
most hardness measures, raw water supplies derived
from the Colorado River at or below Lake Mead would
be classified as very hard.

Boiler feed and cooling water comprise a major portion
of water used by industry in the basin. Mineral quality
of boiler feed water is an important factor in the rate
of scale formation on heating surfaces, degree of
corrosion in the system, and quality of produced
steam. In cooling water systems, resistance to slime
formation and corrosion is affected by mineral quality.

The physical impacts of salinity upon consumptive uses
of water were translated into economic values by
evaluating how each user might alleviate the effects of
salinity increases.

The alternatives available to Irrigation water users are
influenced by the availability of additional water. The
primary means of combating detrimental salinity are to
switch to salt tolerant varieties of crops or to apply
more irrigation water and leach out excess salts.

(1) If the irrigator does nothing, he will suffer
economic loss from decreased crop yields.

(2) If additional water is available, root zone
sal inity may be reduced by increasing leaching water
applications. The irrigator would incur increased
costs for purchase of water, for additional labor for
water appl ication, and for increased appl ication of
fertilizer to replace the fertilizer leached out.

(3) If no additional water is available, the irrigator
can increase the leaching of salts from the soi I by
applying the same amount of water to lesser
acreage. This, of course, results in an economic loss
since fewer acres of crops can be grown.

(4) By changing the management regime and
applying alternative production practices, some
salinity effects can be mitigated but only by

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