WSP01897

• File Number: 8270.100
• Description: Colorado River Basin Water Quality/Salinity -- Misc Water Quality
• Basin: Colorado Mainstem
• Water Division: 5
• Date: 1/1/1977
• Author: USDOI
• Title: Quality of Water - Colorado River Basin - Progress Report No. 8 - January 1977
• Water Supply Pro - Doc Type: Report/Study

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CAUSES OF SALI~ITY

The small amOunt of data presently available gives indications of
much variation in the amount of pickup from land due to irrigation.
The estimated salt pickup in this report for projects Without specific
information is based on values of zero and 2 tons per acre from newly
irrigated land. Zero or minimum conditions Occur generally after
Initial leaChing in areas where soils are loose and contain very little
salt. The 2-ton-per-acre value was selected as the higher end of the
range for the average pickup over a project area. It was also assumed
in this report no additional pickup would result from supplemental water
applied to presently irrigated lands. On projects where detailed in-
formation on salt pickup is available through use of models or by special
investigations, these more specific figures were used.

3. MuniCipal and Industrial Sources of Salinity

Salt loads contributed to the Colorado River system by municipal
and industrial sources are generally minor, totaling about I percent of
the baSin salt load. Future increases in salt loads from these sources
are expected to be small relative to the total basin salt burden and
will have only a minor effect on salinity levels.

With the exception of concentrated return flows from the Las Vegas
area. most municipal and minor industrial wastes are relatively low in
total salt load in comparison with natural and egricultural sources, and
complete elimination of such waste discharges would have little effect
on salinity concentrations in the main river system. Since these wastes
are point Sources of salinity, control of a Source could be achieved if
salinity levels in the waste being discharged (i.e.. industrial brines)
warrant such COntrol.

The recent energy shortage has caused an increase of interest
for construction of large energy producing industries within the Colo-
rado River Basin. With emphasis placed on imprOving the water quality
in the basin. these industries have been under pressure by State and
Federal agencies to prevent the return of salts to the river by con-
suming all water diverted for use.

B. Increased Concentration from Water Depletions

Addition of salts to the river sYStem is not the only cause of
increased salinity concentrations. The depletion of water of better
quality than in do~~stream reaches produces a concentrating effect on
the waters of the do~nstream reaches. This concentrating effect occurs
to a greater degree when the diverted salts return to the riVer than
when they are depleted along vith the Water.

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