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<br />Projected Plan of Operation Under Criteria - Water Year 1988
<br />
<br />Determination of "602(a) Storage"
<br />
<br />Section 602(a)(3) of the Colorado River Basin Project Act of
<br />September 30, 1968 (Public Law 90-537), provides for the
<br />storage of Colorado River water, not required to be released
<br />under article III(c) and III ( d) of the Colorado River Compact
<br />in Upper Basin reservoirs, to tbe extent tbe Secretary of tbe
<br />Interior (Secretary) finds it necessary to assure Compact
<br />deliveries without impairment of annual consumptive uses in
<br />the Upper Basin.
<br />
<br />Article II of tbe "Criteria for Coordinated Long-Range
<br />Operation of Colorado River Reservoirs" (Operating
<br />Criteria) provides that tbe annual plan of operation shall
<br />include a deterIUination by tbe Secretary of the quantity of
<br />water considered necessary to be in Upper Basin storage as
<br />of September 30 of the current year,
<br />
<br />Tbis determination shall consider all applicable laws and
<br />relevant factors induding, but not limited to tbe following: (a)
<br />historic stream flows; (b) the most critical period of record; (c)
<br />probabilities of water supply; (d) estimated future depletions
<br />in tbe Upper Basin, induding the effects of recurrence of
<br />critical periods of water supply; (e) the 'Report of the
<br />Committee on Probabilities and Test Studies to the Task
<br />Force on Operating Criteria for the Colorado River,' dated
<br />October 30, 1%9, and sucb additional studies as the Secretary
<br />deems necessary; and (0 the necessity to assure that Upper
<br />Basin consumptive.uses are not impaired because of failure to
<br />store sufficient water to assure deliveries under Section
<br />602(a)(I) and (2) of Public Law 90-537,
<br />
<br />Taking into consideration these relevant factors, the Secretary
<br />has determined that the active slorage in Upper Basin
<br />reservoirs forec~st for September 30, 1988, exceeds tbe
<br />'602( a) Storage' requirement under any reasonable range of
<br />assumptions which might be applied to those items previously
<br />listed, Therefore, the accumulation of "602(a) Storage' is not
<br />the criterion governing the release of water during the current
<br />year,
<br />
<br />Mexican Treaty Obligations
<br />
<br />Annual calendar year schedules of monthly deliveries of water
<br />in the limitrophe section of the Colorado River, allotted in
<br />accordance with tbe Mexican W aterTreaty signed in 1944, are
<br />formulated by tbe Mexican Section and presented to the
<br />United States Section, International Boundary and Water
<br />Commission (Commission), before the beginning of each
<br />calendar year,
<br />
<br />Upon 30 days advance notice to the United States Section,
<br />Mexico bas tbe right to modify, witbin the total scbedule, any
<br />monthly quantity prescribed by the schedule by not more tban
<br />20 percent. During water year 1987, Mexico received a total
<br />delivery of 6,130,000 acre-feet at the Northerly International
<br />Boundary (NIB),
<br />
<br />Of tbe 6,130,000 acre-feet of mainstem Colorado River water
<br />reaching the NIB, about 3,36 MAF were delivered tbrough
<br />tbe Pilot Knob Powerplant and Wasteway from the
<br />All-American Canal, An estimated 2.59 MAF were released
<br />through Laguna Dam, Tbe remainder of tbe flow at NIB was
<br />made up of return flows to tbe Colorado River below Laguna
<br />Dam, and returns to tbe Gila River below the gaging station
<br />near Dome, as well as small Gila River releases from Painted
<br />Rock Reservoir,
<br />
<br />Because of the current water supply conditions, tbe United
<br />States will make scheduled deliveries of 1,7 MAF of Colorado
<br />River water to Mexico in calendar year 1988, Under most
<br />probable water supply conditions, flow at the NIB would total
<br />approximately 4.3 MAF during calendar year 1988, Such
<br />release of water is based upon average runoff conditions for
<br />the year, Should the runoff during 1988 be substantially above
<br />average, significant releases for flood control purposes could
<br />be required from Hoover Dam, Representatives of the
<br />Republic of Mexico will be kept informed of operating
<br />schedules through the United States Section of the
<br />Commission,
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