WSP00896

• File Number: 8282.600.10
• Description: Colorado River Operating Annual Reports
• Basin: Colorado Mainstem
• Date: 1/1/1984
• Author: USDOI/BOR
• Title: Operation of the Colorado River Basin 1984 Projected Operations 1985
• Water Supply Pro - Doc Type: Publication

Proiected Plan of Operation
Under Criteria -
Water Year 1985

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Left spillway tunnel constructIon, Glen Conyon Oem.

. Determination of 1l602(a) Storage"

Section 602(0)(:3) of the Colorado River
Basin Project Act of September 30. 1968
(Public law 90-537), provides for the
storage of Colorado River water, not
required 10 be released under article lII(c)
and lII(d) of the Colorado River Compact in
Upper Basin reservoirs, to the ex.lent the
Secretory of the Interior (Secretory) finds it
necessary 10 assure compact deliveries
without impairment of annual consumpti....e
uses in the Upper Basin.

Article II of the "Criteria for Coordinated
long-Range Operation of Colorado River
- Reservoirs.." -(Operating Griteria) -provides-
that the annual plan of operation shall
include 0 determination by the Secretary of
the quantity of water considered necessary
to be in Upper Basin storage os of
September 30 of the current year.

This determination shall consider 011
applicable laws and relevant factors
including, but not limited to the following;
(0) historic streamflows; (b) the most
critical period of record: (c) probabilities of
water supply; (d) estimated future
depletions in the Upper Basin, including the
effects of recurrence of critical periods of
water supply: (e) the "Report of the
Committee on Probabilities and Test Studies
to the Task Force on Operating Criteria for
the Colorado River," dated October 30,
1969. and such additional studies as the
4

1984 left spillway tesf. Glen Conyon Dom.

Secretary deems necessary: and (f) the
necessity to assure that Upper Basin
consumptive uses are not impaired because
of failure to store sufficient water to assure
deliveries under' Section 602(0)(1) and (2) of
Public law 90-537.

Taking into consideration these rele....ant
factors, the Secretary has determined that
the active storage in Upper Basin reservoirs
forecast for September 30. 1985, exceeds
the "602(0) Storage" requirement under any
reasonable range of assumptions which
might be applied to those items previously
listed. Therefore, the accumulation of
"602(0) Storage" is not the criterion
governing -the release- of"woter-during-the-
current year.

Mexican Treaty Obligation.

Annuol calendar year schedules of monthly
deliveries of water in the limitraphe section
of the Colorado River, allotted in
accordance with the Mexican Water Treaty
signed in 1944. are formulated by the
Mexican Section and presented to the
United States Section. International
Boundary and Water Commission
(Commission), before the beginning of each
calendar year.

Upon :30 days advance notice to the United
States Section. Mexico has the right to
modify, within the total schedule. any

i
Havosu Pumping Plant ond switchyord.

monthly quantity prescribed by the schedule
by not more than 20 percent. During
water year 1984. Mexico received a total
delivery of about 16,596,000 acre-fe~t at the
Northerly International Boundary.

Of the 16.596.0Cl0 acre.feet of mainstem
Colorado River water reaching the
Boundary, about 5.119,000 acre-feet was
delivered through the Pilot.Knob
Powerplant from the AII.American Conal.
An estimated 10,719,000 acre-feet was
released through laguna Dam. The
remainder of the flow at the Northerly
International Boundary was made up of
return flows to the Colorado River below
[a-gunci Dam~ arid- returns to" the Gila River
below the gaging station near Dome. as
well as Gila River flood control releases
from Painted Rock Reservoir.

Because of the current water supply
conditions, the United States will make
scheduled deliveries of 1.700,000 acre.feet
of Colorado River water to the Republic of
Mexico in calendar year 1985. This release
of water is based upon average runoff
conditions for the year. Should the runoff
in water year 1985 be substantially above
average. significant releases far flood
control purposes could be required from
Hoover Dam. Representatives of the
Republic of Mexico will be kept informed of
operating schedules through the United
States Section of the Commission.