WSP09978

• File Number: 822.600.10
• Description: Colorado River Annual Operating Plan - Annual Reports
• Basin: Colorado Mainstem
• Date: 1/1/1994
• Author: USDOI/BOR
• Title: Annual Operating Plan
• Water Supply Pro - Doc Type: Annual Report

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1944 Mexican Water Treaty Delivery, The guaranteed annual quantity of 1,850. MCM
(1.500 MAP) of water will be delivered to Mexico during calendar year 1994 in
accordance with Article 15 of the 1944 Mexican Water Treaty and Minute No. 242 of the
IBWC,

Reservoir Operations. The technical studies based on the probable maximum reservoir
inflow scenario and June 3D, 1993, reservoir storage conditions project flood control
releases from Hoover Dam in January, 1994, of 538 m'ls (19,000 cfs)(2) and additional
releases during November through December, '1994, 10 build the minimum required
January 1, 1995, flood control space. The most probable reservoir inflow scenario does
not project any required flood control releases from Hoover Dam in 1994.

Releases to avoid anticipated spills from Glen Canyon Dam are not expected, except for
water supply assumptions greater than the probable maximum, Water releases from each
of the Colorado River reservoirs will be in accordance with minimum flow requirements, .
reservoir operating criteria, and target storage elevations. The resulting operation will
serve all authorized project purposes at each of the reservoirs.

1993 OPERATIONS SUMMARY AND RESERVOIR STATUS

Water year 1993 signalled the end of six years of drought within the basin. Basinwide
precipitation during 1993 was well above average. The high precipitation also translated
into a well above average snowpack. At the beginning of the runoff season basinwide
snowpack was approximately 140. percent of average and above normal precipitation was
received throughout most of the runoff season. A weather pattern of southerly storms
developed during the snow accumulation season, As a result, the northern portion of the
basin had average to slightly above average snowpack levels, and the central and southern
portion of the basin had well above average snowpack levels. These factors combined to
produce a near average runoff in the Green River, a 20. percent exceedance runoff (values
exceeded 20. percent of the time) in the Gunnison and San Juan Basins, and a 25 percent
exceedance inflow (values exceeded 25 percent of the time) into Lake Powell,

Even though snowpacks in the Gunnison and San Juan basins were similar to those during
the 1983 water year, only minor flooding occurred because temperatures were fluctuating
and adequate time was available to evacuate Blue Mesa and Nav,yo reservoirs as
necessary, Minor flooding also occurred in the Jensen, Utah, area on the Green River
just downstream of its confluence with the Yampa River.

Unregulated inflow into Lake Powell is expected to be 17,0.74 MCM (13.841 MAP),
approximately 120 percent of the long term average, in water year 1993. This inflow,

(2) units of flow used in this document are cubic meters per second (m'/s), followed by
equivalent cubic feet per second (cfs)

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