WSP03818

• File Number: 8276.700
• Description: Colorado River Indian Reservation Unit - Colorado River Salinity Control Program
• State: AZ
• Basin: Colorado Mainstem
• Date: 10/1/1979
• Title: Colorado River Indian Reservation Unit Status Report - Colorado River Water Quality Improvement Program Irrigation Source Division
• Water Supply Pro - Doc Type: Report/Study

The amounts tabulated for years 1968 and 1969 were estimated
using data from less frequent measurements than are made under the
ISSP program, and have a lower confidence level. However, they are
judged to be adequate for this preliminary analysis.
Figure 3 shows the quantities of diversion water and return flow
for each year of record, their salinity in milligrams per liter, their
salt content in tons, and the net salt discharge in tons,
An attempt was made to evaluate the reasons for the variation in
net salt discharge as shown on the preceding page, It was found
that the years with the three relative highs were years of relatively
low per acre water use, apparently involving interruptions of irriga-
tion operations. In 1976 a tropical storm caused unusually heavy late
summer rain, which apparently caused more of a reduction in diver-
sions than drainage, Higher than average rainfall also occurred in
1970 and 1972 and the timing of rainfall may have interfered with
irrigation deliveries, but this correlation is not strong. The varia-
tions are discussed further in a following section of this chapter.
The Boyle Engine.ering Corporation was retained by the Bureau
of Reclamation in 1975 to gather data on irrigation efficiency and
agricultural drainage, and to make a preliminary evaluation of whether
water system improvements would reduce salt discharge to the river,
The results of the study were presented in a report entitled "Salinity
Control and Irrigation System Analysis, Colorado River Indian
Reservation," August 1976. [2]
Using primarily data from 1974 operations, Boyle Engineering
concluded that the Reservation received 779,036 tons of salt and
discharged 647,608 tons. The difference of 131,428 tons was retained
on the Reservation. The various components of the water and salt
budgets are on Table 1, which shows that a substantial amount of
w~ter ,and salt enters the Reservation in addition to Colorado ~d'24 5
diverSlOns , 0
The Boyle estimate can be reconciled with the Bureau of
Reclamation estimate for 1974 if certain unmeasured inflows are added
to the latter. The Bureau of Reclamation ISSP data include only
diversions at Headgate Rock Dam and discharges in the three drains

12