WSP07317

• File Number: 8210.140.20
• Description: Colorado River Basin Organizations and Entities - Colorado River Basin States Forum - California
• State: CA
• Basin: Western Slope
• Date: 1/1/1971
• Author: Myron B Holburt
• Title: Annual Report for the Calendar Year 1970
• Water Supply Pro - Doc Type: Annual Report

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operation of Minute No. 218, the required
makeup from storage has cost users in the
United States a total of 201,100 acre-feet, an
average of 40,200 acre-feet per year. The an-
nual average salinity of Colorado River water
delivered to Mexico under the Treaty at the
Northerly International Boundary decreased
from 1,330 to 1,278 parts per million (ppm)
during the five-year period.
During the fifth year of Minute No. 218
operation, the daily average salinity of the
deliveries to Mexico at the Northerly Inter-
national Boundary varied from about 1,000
ppm to 1,450 ppm. The aVerage salinity of the
Wellton-Mohawk drainage waters in 1970
was estimated at 3,790 ppm, which is about
340 ppm less than that of 1969. Plate 8 shows
the salinity and flow of the Wellton-Mohawk
Outfall Drain, the Colorado River at Impe-
rial Dam, and at the Northerly International
Boundary with Mexico.
Mexico has also been working on facilities
to reduce the impact of the river's salinity on
its lands. An $18,000,000 canal rehabilitation
project in Mexicali Valley, initiated in June
1969, was aoout IS percent complete at the
end of 1970. This work consists principally of
concrete lining of the Valley's canal system.
By reducing seepage losses and phreatophyte
consumption, this project will increase the
ability of Mexican irrigators to cope with
high salinity water.
Construction work on 12 new drainage
wells on the Yuma Mesa and on a conveyance
conduit was completed during 1970 by the
Bureau of Reclamation. The conduit dis-
charges water pumped from the Yuma area
ground water basin into the Colorado River
at a point about 6 miles upstream from More-
los Dam.
The U. S. Geological Survey completed
analog model studies and a report on the
Yuma area ground water basin and presented
the results to Mexican engineers in February
1970. The model demonstrated that under-
ground water in the Yuma area primarily
originates as deep percolation from irriga-
tion of lands in the United States and not
from the river's mainstem; and that the effect

of pumping the 12 Yuma Mesa wells on the
flow of ground water to Mexico would be
insignificant.

Establishment of Water Quality Standards
The setting of numerical salinity criteria
for the Colorado River has been postponed
by the Colorado River Basin states with the
concurrence of the Secretary of the Interior
until sufficient information IS available to as-
sure that salinity standards will be workable.
The basin states have all adopted their indi-
vidual version of an "anti-degradation state-
ment" which declares that, subject to certain
exceptions, each state Of poses the further
degradation of its natura waterways.
On June 4,1970, the State Water Resources
Control Board (SWRCB) adopted bacterio-
logical quality criteria for the Colorado Riv-
er. The SWRCB also considered radiological
and temperature objectives during 1970,
postponed further action on the former
pending additional research, and held several
hearings in attempting to adopt acceptable
temperature objectives. The problem is to set
forth policies that would provide the desired
degree of control of thermal wastes and at the
same time permit the return of agricultural
drainage water to the Colorado River.
On April 16, 1970, the State Water Re-
sources Control Board held a public hearing
on temperature objectives for all existing
California water quality control policies. For
the Colorado River, the proposed objectives
provided that a 5' F rise above background
temperature would be permitted for the
months of October through March, and a 2.
F rise for the remainder of the year. The
Chief Engineer of the Colorado River Board
presented a statement at the public hearings
which pointed out that irrigation water users
have no means by which return flows can be
controlled and recommended that numerical
temperature limits not be set that could pre-
vent irrigation districts along the Colorado
River from beneficially using their water.
Additional recommendations were also made
to clarify certain terms and to limit individ-
ual discharges of industrial water to a max-
imum temperature. The State Department of
Fish and Game proposed a modification to
the proposed objectives concerning warm
water fisheries which was supported by the

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