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

002693

,.' ,-<{\.,.

streamflow can increase sea-water incursion and
reduce seasonal flushing by floods; and (2) the
increase in use of water for irrigation and other
economic activity as a result of development increases
the waste loadings discharged to the estuary.
Irrigated agriculture, the largest present and future
consumptive use of water, results in greater salinity,
nutrients, and pesticide loads on surface and
groundwaters. Salinity is the most widespread water
quality problem of the Pacific Southwest, and the
most difficult to solve.

Natural sources of salinity and nutrients include:
(1) saline groundwater accretions, spring discharges,
and runoff in the Colorado River Basin; (2) saline
discharges from abandoned gas or oil wells in the
Tuolumne River Basin in California; and (3) the
nutrient-rich tributaries of Klamath Lake, Oregon,
and Clear Lake, California.

In the Colorado River Basin salinity problems are
most serious, and will continue to increase unless
constructive measures are implemented to alleviate
them. The 1965 level of Colorado River salinity was
about 590 mgfl (milligrams per liter, roughly
equivalent to parts per million) at Lee Ferry, and
about 840 mg/I at Imperial Dam - where
approximately 6 million acre-feet are diverted or
released annually, primarily for irrigation. The level
of salinity at Imperial Dam damages the agricultural
areas by reducing crop yield, by damaging salt-sensi.
tive plants, by increasing soil drainage problems, and
by increasing operation and maintenance costs. The
salinity of the Colorado River water also increases the
cost of treatment and service of suitable water to the
diverters for municipal, industrial and domestic use.
If water development projects are constructed as
projected in the framework plans and the river is not
augmented, and no salinity control measures are
taken, the salinity at Lee Ferry and at Imperial Dam
may increase as shown in figure 25. Reduction of the
above salinities by augmentation with better quality
water will vary depending on the amount and place of
augmentation in the Colorado River system and with
the amounts released to Mexico.
The impact of salinity increaseswill be negligible
in the Upper Colorado Region, although significant
increases in concentrations are projected. Some 10'
calized problems may occur. Increases in salinity,
however, in the lower reaches of the river basin are
greatly magnified, and are projected to have major
adverse impacts.
The level of salinity within the Lower Colorado
Region will be dependent upon the implementation
of a salinity control program within the entire Colo.
rado River Basin. Augmentation or desalting in the
Lower Basin are other possible solutions.
A salinity control program for the Colorado River
Basin has been included in the framework plan.

Water Quality

1500

0:
W
I-
.J
;, 1000
:Ii
<(
0:
(!)
::;
.J
:Ii

At Imperial Dam Without Program
k----t----

A~ Imperial Dam With Program
/

/.

At Lee Ferry Without Program
--
--

--
-

--

>- 500
!:
z
::;
<(
'"

At Lee Ferr With Pro ram

o
1965

1980

2000

2020

Fignre 25.-Colorado River water salinity.

Further detailed studies and pilot projects to deter-
mine the desirability and feasibility of the control
program are needed. Any depletions of water resulting
from measures included in the basinwide salinity
improvement program will have to be prorated to the
beneficiaries in accordance with the benefits.
Although not a serious problem now, confined
animal raising (feedlots, poultry "factories," etc.) is a
potentially serious water quality problem due to the
sheer magnitude of the projected waste loads from
this source.
Projected increases in recreation will result in an
increased amount of human waste disposal in land
and water areas. Some of these areas cannot accept
such disposal without serious effects on the local
water quality.
In the Great Basin, the combination of increa&jpg
consumptive use of water upstream and the rising
salinity and nutrient loadings will degrade terminal
lakes. All sewage waste water will be exported from
the Lake Tahoe Basin by 1972 in order to protect the
Lake's water quality.

Plan Response

The base plan includes source control and
treatment of pollutants as the most feasible means of
solving most water pollution problems.
Source control of municipal and industrial wastes
consists of providing a minimum of secondary
biological treatment or its equivalent.
Systems for treatment of irrigation drainage waters
to remove most polluting constituents have not yet

69