WSP03527

• File Number: 822.600.10
• Description: Colorado River Annual Operating Plan - Annual Reports
• Basin: Colorado Mainstem
• Date: 1/1/2003
• Author: USDOI/BOR
• Title: Annual Operating Plan
• Water Supply Pro - Doc Type: Annual Report

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2002 OPERATIO;\S SVM.\IARY A;\O RESER\OOlR STATUS

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Extremely dry hydrologic conditions were observed in the Colorado River basin in water year 2001.
Basinwide precipitation was only ~8 percenl of average and snowpack accumulations were much
below nomlal le....e1s. As the spring snowmelt season began on April I. 2001. snowpack levels
throughout the Colorado River Basin were generally less than 50 percent ofa\"erage. The situation
was particularly severe in the central and southern portions of the Upper Colorado River basin. \tany
reservoirs in the Colorado River Basin recorded record low inllows during 1001. These included
:-.Ja\'ajo Reservoir. Blue ~tesa Reservoir and Lake Powell. Unregulatedl]! inflow into Lake Powell
during the April through July runofTperiod in 2002 was only 1.12 maf( 1.380 mcm) or 14 percent of
the 30 year averagel21. Total unregulated inflow into Lake Powell for water year 2002 was only 3.06
maf(3.780 mcm) or 25 percent of average. This was the lowest recorded since the closure ofGlcn
Canyon Dam in 1963. The previous low was observed in 1977 when water year unregulated inflow
was 3.66 maf(4.510 mcm) or 30 percenl of average.

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I\"ot only was water year 2002 a very low year for runoff in the Colorado River basin. but It also
marked the third consecutive year with below average inflow into Colorado Ri,"er reservoirs.
Reservoir storage continued to decline for the third straight )'ear. Storage in Lake Powell decreased
by 4.67 maf (5.760 mcm) in 2002. Storage in reservoirs upstream of Lake Powell decreased by
approximately 1.06 maf (1.300 mcm). In Lower Basin reservoirs. storage decreased by 2.80 maf
(3.460 mcm). At the beginning of water year 2002. Colorado River total system storage was 76
~ ~. - ~
percent of capacity. Total Colorado River system storage decreased by approximately 8.52 maf
(10.500 mcm) during waler year 2002. As of September 30. 2002 total system storage was 64
percent of capacity.

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E,'en Ihough Colorado River reservoir storage has been reduced. during 2002. all deliveries of water
10 meet valid obligations pursuant to applicable provisions of "The Law of the River" were
maintained.

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Preliminary Colorado River water delivery accounting data for calendar year (CY) 2002. compiled
pursuant to Article V of the Decree. indicated that requests for walerdcliveries by agricultural users
in California during CY 1002 had the pOlential to exceed the maximum amounl of water available
under the detemlinations made in the 2001 AOP approved and transmitted on January 14. 2002. In
light of the potential for such overuse within Ihe Lower Basin. and after consuhation with members
of the CR~1\\'G. a supplement to the 2002 ADP was approved on November 22. 2002. The

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(I) Unregulated inflow adjusts for the effects of operations at upstream reservoirs. It is computed
by adding the change in storage. and the evaporation losses from upstream reservoirs to the
observed intlow. Unregulated inflow is used because it pro,'ides an inflow time series that is not
biased by upstream operations. and more closely resembles natural flow conditions.
(:'lntlow statistics throughout this documenl will be as compared 10 30 year averages.

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December 13. 2002

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