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Projected Plan of Operation Under Criteria - Water Year 1986 Determination 01 "602(a) Storage" Section 602(aX3) of the Colorado River Basin Project Act 01 September 30, 1968 (Public Law 90.537), provides for the storage of Colorado River water, not required to be released under article 111(c) and III(d) of the Colorado River Compact in Upper Basin reservoirs, to the extent the Secretary 01 the Interior (Secretary) tinds it necessary to assure compact deliveries wIthout impairment of annual consumptive uses in the Upper Basin. Article II of the "Criteria for Coordinated Lmg.Range Operation of Colorado River Reservoirs" (Operating Criteria) provides that the annual plan of operation shall Include a determination by the Secretary of the quanllly 01 waler considered necessary to be in Upper BaSin slorage as 01 September 30 of the current yea r. This determination shall consider all applicable laws and relevant factors Including, but not limited to the following: :a) historic streamllows; (b) the most :f1tlcal period 01 record: (c) probabilities Jf water supply; (d) estimated future jepletions In the Upper Basin, including .he eflects 01 recurrence of critical Jeriods 01 water supply; (e) the "Report of the Committee on Probabilities and Test Studies to the Task Force on Operating Criteria lor the Colorado River," dated October 30, 1969, and such addilional studies as the Secretary deems necessary; and (I) the necessity to assure thaI Upper Basin consumptive uses are nol impaired because of failure to store sufficient water to assure deliveries under Section 602(aX1) and (2) of Public Law 90-537. Taking into consideration these relevant factors, the Secretary has determined thai the active storage in Upper Basin reservoirs forecast for September 30, 1986, exceeds the "602(a) Storage" requirement under any reasonable range of assumptions which might be applied to those items previously listed. Therefore, the accumulation of "602(a) Storage" is not the criterion governing the release of water during the current year. Mexican Treaty Obligations Annual calendar year schedules of monthly deliveries of water in the limitrophe section of the Colorado River, allotted in accordance with the Mexican Water Treaty signed in 1944, are formu- lated by the Mexican Section and plllway Repel;! B~ue Mesa DO:Im 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 monthly quantity prescribed by the schedule by nol more than 20 percent. During water year 1985, Mexico received a total delivery of about 13,030,000 acre. feet at the Northerly International Boundary. 01 the 13,030,000 acre-Ieet of mainstem Colorado River water reaching the Boundary, about 4,600,000 acre-feet were delivered through the Pilot Knob Power. plant from the All-American Canal. An estimated 7,500,000 acre-feet were released through Laguna Dam. The remainder 01 the flow at the Northerly Internationai Boundary was made up of refurn flows to the Colorado River below Laguna Dam, and 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 1986. This release of water is based upon average runoff conditions for the year. Should the runoff in water year 1986 be substantially above average, significant releases for flood control purposes could be required from Hoover Dam. Represen, tatives oj the Republic of Mexico will be kept informed of operating schedules through the United States Section of the Commission. Regulatory Wastes . Deliveries to Mexico consist of river water delivered to Imperial Dam and waste and drainage return flows from water users below Imperial Dam. In addition to assuring normal water deliveries, the small amount of regulatory storage space in Imperial, Laguna, and Senator Wash Reservoirs was used at times to limit potential downstream flood damages during water year t 985. Regula- tory waste for water year 1986 will depend on the actual hydrologic condi- tions occurnng during that time.