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OPERATION OF THE COLORADO RIVER BASIN 1991 PROJECTED OPERATIONS 1992 21st ANNUAL REPORT
30

OPERATION OF THE COLORADO RIVER BASIN 1991 · PDF fileOPERATION OF THE COLORADO RIVER BASIN 1991 ... Basin Project Act of1968 Public Law90-537. ... 6506 6491 6485 8,058 Acres 18 Miles

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Page 1: OPERATION OF THE COLORADO RIVER BASIN 1991 · PDF fileOPERATION OF THE COLORADO RIVER BASIN 1991 ... Basin Project Act of1968 Public Law90-537. ... 6506 6491 6485 8,058 Acres 18 Miles

OPERATION OF THE COLORADO RIVER BASIN 1991

PROJECTED OPERATIONS 1992

21st ANNUAL REPORT

Page 2: OPERATION OF THE COLORADO RIVER BASIN 1991 · PDF fileOPERATION OF THE COLORADO RIVER BASIN 1991 ... Basin Project Act of1968 Public Law90-537. ... 6506 6491 6485 8,058 Acres 18 Miles

COLORADORIVE R

/'

BAS " N

location Map

Page 3: OPERATION OF THE COLORADO RIVER BASIN 1991 · PDF fileOPERATION OF THE COLORADO RIVER BASIN 1991 ... Basin Project Act of1968 Public Law90-537. ... 6506 6491 6485 8,058 Acres 18 Miles

CONTENTS

. 5

. 7

232324

.91113

1517192122

25......... 27

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1Authority for Report 1A£tual Operations Under Criteria - Water Year 1991 . . . . . . . . . . . . . . . .. 2Projected Plan ofOperation - Water Year 1992

Determination of "602(a) Storage" 3Mexican Treaty Obligations 3Projected Plan . . . . . . . . . . . . . . 4

Upper Basin ReservoirsFontenelle Reservoir (Green River) .Flaming Gorge Reservoir (Green River)Wayne N. Aspinall Unit - Blue Mesa, Morrow Point, and

Crystal Reservoirs - (Gunnison River) . . .....Navajo Reservoir (San Juan River)Lake Powell (Colorado River)

Lower Basin ReservoirsLake Mead (Colorado River)Lake Mohave (Colorado River)Lake Havasu (Colorado River) .

River Regulation. . . . . . . . . .Flood Control . . . . . . . . . . . . . .Beneficial Consumptive Uses

Upper Basin Uses and LossesLower Basin Uses and· LossesWater Use by States . . . . . . . . . . . . . .

Power Operations and Major Maintenance ActivitiesUpper Basin - Colorado River Storage Project .Lower Basin . . . . . . . . . . . . . . . . . . . . . . . .

United States

Department of the Interior

Bureau of Reclamation

January 1992

Prepared pursuant to the Colorado River

Basin Project Act of 1968

Public Law 90-537

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Introduction

The operation of the Colorado River Basin during the pastyear and the projected operation for the current year reflectflood control, river regulation, beneficial consumptive uses,hydroelectric _power generation, water quality control,enhancement of fish and wildlife, recreation, and ColoradoRiver Compact requirements.

Storage and release ofwater from the Upper Basin reservoirsare governed by all applicable laws and agreementsconcerning the Colorado River, including the impoundmentand release of water in the Upper Basin required by Section602(a) ofthe Colorado River Basin Project Act of September30, 1968 (Public Law 90-537). The operation of the LowerBasin reservoirs reflects Mexican Treaty obligations andLower Basin contractual commitments.

Nothing in this report is intended to interpret the provisionsof the Colorado River Compact (45 Stat. 1057), the UpperColorado River Basin Compact (63 Stat. 31), the Water Treatyof 1944 with the United Mexican States (Treaty Series 994, 59Stat. 1219), the United States/Mexico agreement in MinuteNo. 242ofAugust 30, 1973, (Treaty Series 7708; 24 U ST 1968),the Decree entered bythe Supreme Court ofthe United Statesin Arizona v. California et a!. (376 U.S. 340), the BoulderCanyon Project Act (45 Stat. 1057), the Boulder CanyonProject Adjustment Act (54 Stat. 774; 43 U .S.C. 618a), theColorado River Storage Project Act (70 Stat. 105; 43 U .S.C.620), the Colorado River Basin Project Act (82 Stat 885; 43U.S.C. 1501), the Colorado River Salinity Control.Act (88Stat. 266; 43 U .S.C. 1951), or the Hoover Power Plant Act of1984 (98 Stat. 1333).

1

Authority for Report

Pursuant to the Colorado River Basin Project Act (PublicLaw 90-537) of 1968, I am pleased to present to the Congress,and to the Governors of the Colorado River Basin States, thetwenty-first annual report on the Operation of theColorado River Basin.

This report describes the actual operation of the reservoirs inthe Colorado River drainage area constructed under theauthority of the Colorado River Storage Project Act, theBoulder Canyon Project Act, and the Boulder Canyon ProjectAdjustment Act during water year 1991, and the projectedoperation of these reservoirs during water year 1992, underthe "Criteria for Coordinated Long-Range Operation ofColorado River Reservoirs," (Operating Criteria) publishedin the Federal Register June 10, 1970.

The Operating Criteria and Section 602 ofPublic Law 90-537mandate consultation with representatives of the Governorsof the seven Basin States and the Upper Colorado RiverCotnmission relative to annual plans for operation of theColorado River reservoirs. The 1991 Annual Operating Plan(AOP) was prepared by the Bureau of Reclamation inconsultation with the Governors' representatives of the sevenBasin States, the Upper Colorado River Commission, andothers.

Manuel Lujan, Jr., SecretaryUnited States Department of the Interior

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Actual Operations Under Criteria - Water Year 1991

Climatic conditions in the Colorado River Basin for wateryear 1991, as in 1988, 1989, and 1990 were dry. Precipitationfor the water year was approximately 95 percent of average.The extended drought, however, and the associated soilmoisture deficit caused spring runoff in the Upper Basin tobe considerablybelowaverage. Unregulated April-Julyinflowto Lake Powell was' 5,286,000 acre-feet, 65 percent of thelong-term average. Unregulated runoff is the inflow to LakePowell adjusted for the change in storage of the upstreamreservoirs. Lake Powell recorded a peak regulated inflow of38,000 cubic feet per second on June 17, 1991. The totalunregulated runoff into Lake Powell for the water year was8,385,000 acre-feet, 70 percent of the long-term average.

All of the Upper Basin reservoirs recorded below normalinflows in water year 1991. San Juan River inflow to NavajoReservoir was 98 percent of the long-term average.Unregulated inflow of the Gunnison River to Blue MesaReservoir was 78 percent ofnormal, while unregulated inflowof the Green River to Flaming Gorge Reservoir was 80percent of the long-term average. Inflow to FontenelleReservoir from April through July was 82 percent ofnormal.

Upper Basin reservoirs, Flaming Gorge, Blue Mesa, andNavajo, experienced modest rebounds in storage in water year1991. Storage in Lake Powell and Lake Mead, however, isdown 1.0 and 1.4 million acre-feet, respectively. The October1, 1991, Colorado River system vacant space was 18.6 millionacre-feet. Aggregate Colorado River live storage at the endof the year was 42.2 million acre-feet. Aggregate storagedecreased in water year 1991 by 1.7 million acre-feet.

Total releases from Glen Canyon Dam (deliveries from theUpper Basin to the Lower Basin) for water year 1991 were8.23 million acre-feet. The 1991 operation plan allowed thewater needs of the Lower Basin states to be satisfied, up to 7.5million acre-feet of beneficial consumptive use, during thecalendar year.

During water year 1991, Mexico received a total delivery ofabout 1,390,000 acre-feet at the Northerly InternationalBoundary (NIB). Of the 1,390,000 acre-feet ofColorado River water reaching the NIB, about506,000 acre-feet were delivered through the Pilot KnobPowerplant and Wasteway from the All-American Canal. Anestimated 303,000 acre-feet were released throughLaguna Dam. The remainder ofthe flow at the NIB was madeup of return flows to the Colorado River below Laguna Dam.

2

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Projected Plan of Operation - Water Year 1992

Determination of 'fi02(a) Storage"

Section 602(a)(3) of the Colorado River Basin Project Act ofSeptember 30; 1968 (Public Law 90-537), stipulates thatColorado River water, which is not required to be releasedunder article III(c) and III(d) of the Colorado RiverCompact, be stored in Upper Basin reservoirs to the extentthe Secretary of the Interior (Secretary) finds such storagenecessary to assure compact deliveries without impairment ofannual consumptive uses in the Upper Basin.

Article II of the Operating Criteria provides that the annualplan of operation shall include a determination by theSecretary of the quantity of water considered necessary to bein Upper Basin storage as ofSeptember 30 ofthe current year.

This determination shall consider all applicable laws andrelevant factors including, but not limited to, the following:(a) historic strearnflows; (b) the most critical period ofrecord; (c) probabilities ofwater supply; (d) estimated futuredepletions in the Upper Basin, including the effects ofrecurrence ofcritical periods ofwater supply; (e) the "Reportof the Committee on Probabilities and Test Studies to theTask Force on Operating Criteria for the Colorado River,Hdated October 30, 1969, and such additional studies as theSecretarydeems necessary; and (t) the necessity to assure thatUpper Basin consumptive uses are not impaired because of

. failure to store sufficient water to assure deliveries underSection 602(a)(I) and (2) of Public Law 90-537.

Taking into consideration these relevant factors, the Secretaryhas determined that the active storage in Upper Basinreservoirs forecast for September 30, 1992, exceeds the"602(a) StorageHrequirement under any reasonable range ofassumptions which might be applied to those items previouslylisted. Therefore, the accumulation of "602(a) Storage" is notthe criterion governing the release ofwater during the currentyear.

3

Mexican Treaty Obligations

Annual calendar year schedules ofmonthlydeliveries ofwaterin the limitrophe section of the Colorado River, allotted inaccordance with the Mexican Water Treatysigned in 1944, areformulated by the Mexican Section and presented to theUnited States Section, International Boundary and WaterCommission (Commission), before the beginning of eachcalendar year. Upon 30 days advance notice to theUnited States Section, Mexico has the right to modify, withinthe total schedule, any monthly quantity prescribed by theschedule by not more than 20 percent.

Based on the current water supply conditions, theUnited States will make scheduled deliveries of 1,500,000acre-feet of Colorado River water to the Republic of Mexicoin calendar year 1992. Representatives of the Republic ofMexico will be kept informed ofoperating schedules throughthe United States Section of the Commission.

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Projected Plan

In addition to compliance with the Operating Criteria, severalspecific operati~g issues were addressed during thepreparation of the annual operating plan for water year 1992.Consideration was given to the dry condition of the basin, thevacant reservoir space that currentlyexists, requests for waterby holders of water delivery contracts with the United States,and other rights recognized in Arizona w. California. Theoperating issues addressed which are listed in no particularorder. of priority are: (1) meeting the reasonable beneficialColorado River mainstream consumptive water uses in theLower Division States as provided by the Operating Criteria,(2) the delivery of firm power in accordance with energycontracts, (3) minimum and specific releases for fish andwildlife and recreational purposes, (4) refilling of vacantsystem reservoir storage space, (5) potential for flood controlreleases in years before shortages may occur, (6) waterwasted to the GulfofCalifornia, (7) compliance with the 1944Mexican Water Treaty and Minute No. 242 of the IBWC, (8)the use of allocated but yet undeveloped in the Upper Basin,and in Arizona, and Nevada ofthe Lower·Basin, (9) t~e abilityto store unused water apportionments, (10) guidelines forreservoir filling and drawdown recommended for fishspawning periods in Lake Mead, (11) complying fully withcompact, decree, statutory, and water delivery obligations,and (12) other short- and long-term effects of 1992 water usedecisions.

For 1992 operations, three reservoir inflow scenarios weredeveloped and analyzed. The projected monthly inflowswere based upon current hydrological conditions and thefollowing assumptions: (1) probable maximum, based uponthe annual volume of inflow which would be exceeded about10 percent of the time, (2) most probable, based upon annualvolume of inflow which would be exceeded about 50 percentof the time; and, (3) probable minimum, based upon theannual volume of inflow which would be exceeded about 90percent of the time. Each scenario was adjusted for currentbasin conditions; therefore, the magnitude of the threescenarios does not necessarily match the historical upperdecile, mean, and lower decile inflows, respectively. TheNational Weather Service's computer model, known as theExtended Streamflow Prediction model (ESP), uses current

4

basin conditions as well as historical data to predict a rangeof possible future stream flows. Although there is a wideconfidence band associated with stream flow forecasts madea year in advance, the data are valuable in analyzing thepossible impacts on project uses and purposes. The inflowvolumes resulting from these assumptions were used as inputdata in Reclamation's monthly reservoir operation planningcomputer model, which is used to plan reservoir operationsfor the upcoming 12-month period. With assumed water year1992 inflow and current reservoir storage conditions,projected monthly releases wer·e adjusted until release andstorage levels accomplished project purposes and priorities.

Special long-range studies using Reclamation's ColoradoRiver Simulation System (CRSS) were conducted todetermine whether sufficient quantities of mainstream waterwere .available for release from Lake Mead to satisfyreasonable beneficial consumptive use requests in excess of7,500,000 acre-feet in the Lower Division States. The studieswere conducted using the entire hydrologic record (1906through 1990), utilizing 85 hydrologic sequences indexed byone year. These studies simulated operations 30 years into thefuture to assess the risks ofshortages to all users of ColoradoRiver water for beneficial purposes and evaluated severalspecific parameters.

At several locations in both Upper and Lower Basins,minimum ·instream flows have been established in order topreserve the present aquatic resources downstream ofcertainColorado River dams. In many cases, these resources werepoor or nonexistent prior to the time ofdam construction, andthe subsequent controlled, cool water releases have providedan improved environment for aquatic resources and sportfisheries. However these releases are believed to bedetrimental to endangered endemic species of fiSh. In 1992,studies on the Green River will continue, studies on theGunnison and San Juan Rivers will be initiated in order tobetter understand the water needs ofthe endangered endemicspecies of fish in the basin. In general, controlled releasesallow for an extended recreation season, reduce the high flowperiods, and improve sport fisheries, but may be detrimentalto endemic species of fish.

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UPPER BASIN RESERVOIRS

FONTENELLE RESERVOIR(GREEN RIVER)

Water Year 1991

Water year 1991 marked the second full year of normaloperations for Fontenelle Reservoir since the construction ofa concrete cutoffwall to reduce seepage through the dam. Theconcrete cutoff wall is performing satisfactorily, as seepagepast the dam has been reduced considerably.

The April through July runoff into Fontenelle Reservoir was693,000 acre-feet which was 82 percent of average. Inflow for

the entire 1991 water year was 1,017,000 acre-feet, 85 percentof average. The total release from Fontenelle Dam for wateryear 1991 was 958,000 acre-feet.

Peak inflow to Fontenelle Reservoir was 9,900 cubic feet persecond on June 16, 1991. The reservoir filled in July of 1991.Approximately 150,000 acre-feet of water bypassed thepowerplant's turbines.

ACTUAL RELEASES 1991 FONTENELLE RESERVOIR

Elevation, feet

650664916485

8,058 Acres18 Miles

1lO,OOOKW

344,834233,789194,962

Acre-feetReservoir

Powerplant

Stor~ge CapacityRated HeadMinimum PowerSurface Area, fullReservoir Length, full

Number of UnitsTotal Capacity

j~

/ \b/~ ~~bl~ ----t~~ If

100

THOUSAND ACRE-FEET-"00

300

oONDJ FMAMJ JAS

200

5

Page 9: OPERATION OF THE COLORADO RIVER BASIN 1991 · PDF fileOPERATION OF THE COLORADO RIVER BASIN 1991 ... Basin Project Act of1968 Public Law90-537. ... 6506 6491 6485 8,058 Acres 18 Miles

PROJECTED RELEASES 1992

THOUSAND ACRE-FEET400 r----r---r--......------,r-----r-~-..,...____,-____r_-__r_____,

100 1---+--+---+-------i~-==:M~~-+_____4-_+_----.:~~

200 ~-+-_+_--+---......--+-_+_I__+__~~__+__\__+____l

300 ~-+--+---+---......--+--+--+--~~--+---+-~

Water Year 1992

Since the mean annual inflow of 1.2 million acre-feet farexceeds the storage capacityof345,000 acre-feet, there is littlechance that the reservoir will not fill during water year 1992.

. In order to minimize the high releases that occur in the springand to ensure that the reservoir fills, it will be drawn down toan appropriate level this winter, probably to minimum poolelevation (6463 feet) which corresponds to a volume of93,OOOacre-feet.

Releases should average about 1,200 cubic feet per second(efs) through the fall and winter months. Releases at this levelwill provide an appropriate level ofdrawdown for next season,the water quality of the river for downstream municipal andindustrial uses. Under all but the most adverse inflowassumption, the reservoir is expected to fill in the summer of1992.

PROJECTED UNREGULATED INFLOW 1992

THOUSAND ACRE-FEET800 ,-----r----r---...----,r----r---,.--~---,.--.----.---,

PROB IN

500 t---+--+---+-----1~-+--+--+_~~_+_-_+_~

300 r----+~_+_--+------1f__--+--+--~__I_4_~_4_-_+_~

200 t----t---+---+--t---+--+--#--1fr--~~_._4__+___j

OL.--~_--'--_.....L--.---'''--~_--'--_~-.....l_---''-_-L---'

OCT NOV DEC JAN FEB MAR APR MAY JUN JUL AUG SEP

ACTUAL STORAGE 1991 PROJECTED STORAGE 1992

100 ~~--+--+----1f.---::!!-...tt~..:.W!:I;:::;;oc:..+---+---t---+----1

200 ~-+---lV'l.~ld:----If__--+--+--~'-I-t--+---+------1

THOUSAND ACRE-FEET400 ,--~---'---__---''-----r"---r---........------,.--r--.....,......----,

1::1-~bj~

[~

~ 7~~

~/~

~ ~

300

200

100

THOUSAND ACRE-FEET400

oONDJ FMAMJ JAS

oL--.L_-L-_..l..---lL---L..----L--..L----J.----.l--...1..---l

ONDJ FMAMJ JAS

6

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FLAMING GORGE RESERVOIR(GREEN RIVER)

Water Year 1991

The elevation ofFlaming Gorge Reservoir at the beginning ofwater year 1991 was 6022.9 feet with 3,081,000 acre-feet of livestorage (82 percent ofcapacity). At the end of the water year,th~ elevation was 6031.1 feet. Live storage on September 30,1991 was 3,390,465 acre-feet (90 percent of capacity).

As with other drainage areas in the Upper Colorado RiverBasin, precipitation in the Green River Basin was nearnormal, but the quantity of runoffwas reduced due to the dryantecedent conditions of the basin. Unregulated inflow intoFlaming Gorge Reservoir for water year 1991 was 1,320,000acre-feet, 80 percent of normal. Actual regulated inflow was1,261,000 acre-feet.

Releases from Flaming Gorge Reservoir were maintainedabove the minimum level of800 cubic feet per second for mostof water year 1991. Because of the initiation of research

releases at Glen Canyon Dam, releases from Flaming Gorgewere increased above minimum levels. This was done to giveWestern Area Power Administration (WAPA) moreflexibility in maintaining the power system in the event of anemergency. Even with this increase, releases from FlamingGorge Reservoir averaged only 1,150 cubic feet per secondfor the water year. Although. inflow was below normal, amodest increase in storage was realized for the reservoird~ringwater year 1991.

A limited number of specific releases for research and datacollection for studies concerning endangered fish survivalrequirements were provided from Flaming Gorge in 1991. TheColorado Squawfish is currently being studied as part of theRecovery Implementation Program in the Upper ColoradoRiver Basin.

ACTUAL RELEASES 1991 FLAMING GORGE RESERVOIR

604059465871

42,020 Acres91 Miles

3l08,OOOKW

3,749,0001,062,()()()

233,000

Acre-feet Elevation, feetReservoir

Storage CapacityRated HeadMinimum PowerSurface Area, fullReservoir Length, full

Powerplant

Number of UnitsTotal Capacity

~~, / ~V~~~

[~

200

50

oONDJ FMAM J JA S

100

2~0

150

THOUSAND ACRE-FEET300

7

Page 11: OPERATION OF THE COLORADO RIVER BASIN 1991 · PDF fileOPERATION OF THE COLORADO RIVER BASIN 1991 ... Basin Project Act of1968 Public Law90-537. ... 6506 6491 6485 8,058 Acres 18 Miles

PROJECTED RELEASES 1992

Water Year 1992

Releases for water year 1992 will again be maintained at, orabove normal levels under most probable and probableminimum scenarios. Under all but the most adverse inflowassumption, Flaming Gorge Dam will fill in the summer of1992.

The Green River below Flaming Gorge Dam has beendetermined to be habitat ofColorado Squawfish. Restrictionson releases from Flaming Gorge Reservoir have beenimplemented to improve habitat conditions for youngColorado Squawfish. During water year 1992, releaserestrictions, as recommended by the U.S. Fish and WildlifeService, will be maintained.

THOUSAND ACRE-FEET300 ,-----r----r---,------,----r---,.-----,.---....--~__r-~

PROJECTED UNREGULATED INFLOW 1992

THOUSAND ACRE-FEET1000 r--"--r--....,.-----,-~-~--r-_...,.._--.---_____r-___r____.

PA08 MIN +w aT P 011

800 1---t--+---t-----t--+---+--t--+---4----+----{

800 t----+---+-~I---+--+---I--+-_+_...f--l~-_4_--1

ACTUAL STORAGE 1991 PROJECTED STORAGE 1992

-So PAOS MIN +M PST PF OS ~PA :>8 MA~

~~"""""'!I

..............i~7 ~J

~

~~

/~l.-

2500

THOUSAND ACRE-FEET4000

2000ONDJ FMAM J JA S

3&00

3000

00

¥v

V~~J

~

00

00

38

30

26

2000ONDJ FMAM J JA S

40THOUSAND ACRE-FEET

8

Page 12: OPERATION OF THE COLORADO RIVER BASIN 1991 · PDF fileOPERATION OF THE COLORADO RIVER BASIN 1991 ... Basin Project Act of1968 Public Law90-537. ... 6506 6491 6485 8,058 Acres 18 Miles

WAYNE N. ASPINALL UNITBLUE MESA, MORROW POINT, ANDCRYSTAL RESERVOIRS(GUNNISON RIVER)

Water Year 1991

The Wayne N. Aspinall Unit, is comprised of Blue Mesa,Morrow Point, and Crystal Reservoirs. Blue Mesa providesnearly all of the long-term storage for all three powerplants.Morrow Point provides peaking power, and thus has highlyvariable releases. The primary function of Crystal Reservoiris to regulate the variable Morrow Point releases. Live storagecapacities for Morrow Point and Crystal Reservoirs are117,000 and 17,500 acre-feet respectively.

Even though water year 1991 inflow was only 78 percent ofnormal, the Aspinall Unit filled in early June. The filling ofAspinall Unit facilities during 1991 resulted because onlyminimum releases were made during 1989 and 1990. Theminimum release objective of the Aspinall Unit is to meet thedelivery requirements of the Uncompahgre Valley Projectand to keep a minimum of 300 cfs flowing through the BlackCanyon of the Gunnison National Monument. During 1991flows ofover 4,000 cfs were experienced in the Black Canyonas reservoir inflows ofover 8,000 cfs occurred. To protect theblue ribbon trout fishery in the Black Canyon, releases werecarefully planned to minimize large fluctuations in the dailyand monthly flows. This was accomplished with only minimal

amounts ofwater bypassing the powerplants at Blue Mesa andMorrow Point.

April through July unregulated runoff into Blue MesaReservoir was 601,000 acre-feet, or 78 percent ofaverage. Thetotal unregulated inflow for water year 1991 inflow was854,000 acre-feet, or 78 percent of average. The peakregulated inflow to Blue Mesa was 5,800 cubic feet per secondon June 15, 1991. Releases from Blue Mesa Reservoir totaled758,000 acre-feet for the water year.

Morrow Point Reservoir was operated between elewtions715iand 7160 feet. Side inflow to Morrow Point Reservoir forwater year 1991 was 84,000 acre-feet. A total of 757,000acre-feet was released during the water year, with all but 2,000acre-feet passing though the powerplant.

During water year 1991 the maximum daily release fromCrystal Reservoir was 5,000 cubic feet per second. Theamount that bypassed through the turbine at Crystal was172,000 acre-feet.

ACTUAL CRYSTAL RELEASES 1991 BLUE MESA RESERVOIR

Elewtion, feet

751974387393

9,180 Acres24 Miles

5208,000 KW

829,523249,395

81,070

Acre-feetReservoir

Powerplants (Blue Mesa, Morrow Point, & Crystal)

Storage CapacityRated HeadMinimum PowerSurface Area, fullReservoir Length, full

Number of UnitsTotal Capacity

J~

t( \/ )~

~]

~V[~ ""'"

L- V'"~~

200

so

100

oONDJ FMAMJ JAS

150

THOUSAND ACRE-FEET250

9

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.~

Water Year 1992 PROJECTED CRYSTAL RELEASES 1992

By December 1992, Blue Mesa Reservoir will be drawn down toat least an elevation of7495.0 acre-feet in order to minimize icingproblems in the Gunnison River. Blue Mesa will continue to bedrawn down through April of 1992 to the level that willaccotntnodate the most probable inflow scenario and accomplishthe release objectives with a minimum of powerplant bypasses.Under all but the most adverse inflow scenarios, Blue Mesa isexpected to fill in the summer of 1992. The filling of the reservoirnext year will insure that reasonable specific releases required tostudy the protection and improvement ofhabitat for endangeredfish can be made. The forecasted runoffduring the spring of 1992will be constantly monitored to achieve these objectives.

THOUSAND ACRE-FEET300 .-----r----.----r---,--,-----.----r----r-~-~____.

250 t----+--t--+------ll------r--t--+----+-_+_--+---I

200 ....---+--+--+----lr---+--+--I-+---+---..::~--+-~

150 t-----+--t--+------l---+--~-+-----+-_+_~,...+-~

100 t----+-___+_T-+----ll-----+-~___+_-+----i-_+_--+-~

50 t----+-.....;;poooc--+-----l---+-7fII'C--+--+-----i-_+_--+----I

Morrow Point Reservoir releases are expected to fluctuate up topowerplant capacity during water year 1992. Crystal Reservoirwill be operated to regulate releases from Morrow PointReservoir, to meet downstream requirements for diversionsthrough the Gunnison Tunnel, and to proJect the blue ribbontrout fishery in the Black Canyon. Releases are carefully plannedto minimize large monthly changes in flow below the GunnisonTunnel Diversion. The forecasted runoffduring the springof 1992will be constantly monitored to achieve this objective.

Assuming most probable inflow conditions, releases from CrystalReservoir will range from 1,200 cubic feet per second to themaximum capacity of 4,200 cubic feet per second.

BLUE MESA UNREGULATED INFLOW 1992

THOUSAND ACRE-FEET1500 .-----r----.----r----r--,----r--,...-~-........,.....----y------.

PA08 IN

400 t------r---+---r-----+---t---t--+----+--+---+-----t

300 ....---+--+---+----t---+---+--F------jIlI~-+---+-~

200 t---+--+---+-----l---+---+-+-I-+----::l:~k---Hlr__-+-~

ACTUAL BLUE MESA STORAGE 1991 PROJECTED BLUE MESA STORAGE 1992

800 t--~~d_-t----+-___+_-+--iilif_#_-+---+---t'------f

400 r----+---+--+----+--3lo-=*-::~-.---t-_+_--+------.jI___--I

800 r----r--;----r-------t--r--r----;--;;b;;.....".,...........~-«>

THOUSAND ACRE-FEET1000 r-----r-..,....--r--~---.---.---,---,--.,.-___,r-----,

..)~it

J(" ~

"""""""'~ ./)([~ ~~

~

THOUSAND ACRE-FEET800

700

800

800

500 200 r----+---+--+----+--+--+---+--+---+------.ji-----f

400ONDJ FMAMJ JAS

O~-"----I.--~----I...---'---....a.----'--""--.....L----li-----'

ONDJ FMAMJ JAS

10

Page 14: OPERATION OF THE COLORADO RIVER BASIN 1991 · PDF fileOPERATION OF THE COLORADO RIVER BASIN 1991 ... Basin Project Act of1968 Public Law90-537. ... 6506 6491 6485 8,058 Acres 18 Miles

Elevation, feet

60855990

15,610 Acres33 Miles

1,696,400660,500

Acre-feet

Navajo Reservoir occurred on April 7, 1991 at 5,565 cubic feetper second. The reservoir reached a peak elevation of 6,078.7feet on June 29, 1991.

During May of 1991, release of 3,000 cfs were made in orderto accommodate studies for endangered fish and to flush siltfrom the river bed that has accumulated over the past 2 yearsof minimal release. After the completion of the specificreieases, discharge from the reservoir was reduced to 600 efs.

NAVAJO RESERVOIR

Reservoir

Storage CapacityInactive StorageSurface Area, fullReservoir Length, full

0

-8-~WN TREAt ~ RELE !'SES -e- NIP

0

0

0)~

V \b-V~~

r ~~D-(~ ---'v

30

20

THOUSAND ACRE-FEET

ONDJFMAMJ JAS

40

10

ACTUAL RELEASES 1991

NAVAJO RESERVOIR(SAN JUAN RIVER)

Water Year 1991

As with other drainage areas in the Upper Colorado RiverBasin, precipitation in the San Juan Basin was near normal.Actual inflow to Navajo Reservoir for water year 1991 was937,000 acre-feet, 98 percent of normal. Peak inflow into

The elevation of Navajo Reservoir at the beginning of thewater year was 6061.4 feet with 1,362,138 acre-feet of livestorage (80percent ofcapacity). At the end ofwater year 1991,the elevation was 6077.7 with 1,586,397 acre-feet of livestorage (94 percent of capacity).

11

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PROJECTED RELEASES 1992

Water Year 1992

Navajo Reservoir should fill in 1992. Releases from thereservoir will be held near 600 cfs through the fall and wintermonths and large releases will be made in May and June inorder to provide better spawning conditions for endangeredfish located in the San Juan River. Additionally, specificreleases will be made from the reservoir in order to studyhabitat requirements of the· endangered fish. These specificreleases will be part ofa seven-year study of the habitat needsof the endangered fish in the San Juan River Basin conductedbythe United States Fish and Wildlife Service. After the studyperiod, the data collected will be used to determine flowrequirements for these fish.

THOUSAND ACRE-FEET400 r------r---r---r----r---,---r------r---r--..,....---,-----.

PROS IN

300 t----+---+--+---+--+-----.IF--+---+-\~+----I-----l

200 I----+--+--+---+--+-I--+----+---+-~~----i-----l

100 I----+--+--+---+--#--+--+-+-+~-+-~+-----i~~

PROJECTED INFLOW 1992

THOUSAND ACRE-FEET500,..----r---,---,.----r--...,.....--,.------r--,----r------r---.

ACTUAL STORAGE 1991 PROJECTED STORAGE 1992

1800t---+--+--+---+--+-~~--,IIf~-+--+-~r--~

THOUSAND ACRE-FEET1800 ,-----r--r--r------r---r--~~-~-~---,----,

1400 1---+--+--+---+--+---+----+--4-....::::!IIoooe-~I____--I

1000 l-----L.._--!-_..I.------L_---L.-_..L...---J._--'-_...1...----...J_---J

ONDJFMAMJ JA S

1200 t-----+---;--+---+---+---+----+--4---+----I~~

0

0 V ~ ~.....-tu

~~

l/-~

0

180

140

120

1000ONDJFMAMJ JAS

180THOUSAND ACRE-FEET

12

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LAKE POWELL(COLORADO RIVER)

Water Year 1991

Lake Powell, which is impounded by Glen Canyon Dam, isoperated as part of the Colorado River Storage Project(CRSP) in accordance with governing compacts and laws toprovide conservation storage, river regulation, powergeneration, recreation, and fISh and wildlife enhancement.

Lake Powell began water year 1991 at elevation 3637.6 feetwith a live content of 15,720,000 acre-feet (65 percent full).April through July unregulated inflow to Lake Powell was5,286,000 acre-feet (65 percent ofaverage). Total unregulatedinflow into Lake Powell in water year 1991 was 8,385,000acre-feet, only 70 percent of the 11,900,000 acre-feetunregulated average. Actual regulated inflow for water year1991 was 7,510,000 acre-feet. Regulated inflow to Lake Powellpeaked at 38,000 cubic feet per second on June 17, 1991.

Beginning on August 7, 1991, test interim minimum andmaximum releases and controlled fluctuations wereestablished below Glen Canyon Dam, pending development

and implementation of the interim criteria on November 1,1991. The interim criteria are intended to reduce the effectsof power operations on downstream natural resources untilthe Glen Canyon Environmental Impact Statement iscompleted. Lake Powell has a minimum objective annualrelease of 8.23 million acre-feet, as set forth in the OperatingCriteria. The delivery of the 8.23 million acre-feet, coupledwith continued below normal inflow, reduced live storage atthe'end ofwater year 1991 to 14,699,000 acre-feet (60 percentfull). The reservoir elevation on September 30, 1991 was3628.6 feet, over 70 feet below the maximum pool elevation of3700 feet.

Maintaining a minimum release of 8,230,000 acre-feetannually from Lake Powell combined with the lowestconsecutive 5 years of inflow on record (1987 through 1991),and a refilling of the upstream reservoirs has reduced thestorage of the reservoir below its capacity by approximately9,500,000 acre-feet.

ACTUAL RELEASES 1991 LAKE POWELL

Elevation, feet

370035703490

161,390 Acres186 Miles

Acre-feet

24,322,0009,428,0004,126,000

Reservoir

Storage CapacityRated HeadMinimum PowerSurface Area, fullReservoir Length, full

Powerplant

v~~h

/ ~ / ~V ~b'

[~

THOUSAND ACRE-FEET1200

800

600

1000

400

200

oo N D J F M A M J J A S

13

Number of UnitsTotal Capacity

81,247,000 KW

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Water Year 1992 PROJECTED RELEASES 1992

-s- PROS MIN +M )8T P~OS ~PR )8 MA~

)r'" \/)~~~

l/V ~ ~V 'n~

·1..........- - -.,~800

800

400

THOUSAND ACRE-FEET1400

1000

1200

The reservoir storage is projected to continue to declinethrough the fall and winter, reaching a seasonal low in March1992 of 13,600,000 acre-feet, which is about 82 feet from full.During water year 1992, the minimum objective release of 8.23million acre-feet will be made. Under most probable inflowconditions, the reservoir will recover to only 17,200,000acre-feet which is about 50 feet from full. Due to the extendeddrought, it may take approximately nine years ofaverage inflowto refill the reservoir.

Because the level of Lake Powell has dropped considerablysince 1987, the risk ofreleases greater than poweFplant capacityduring water year 1992 is negligible.

200

o

PROJECTED UNREGULATED INFLOW 1992

THOUSAND ACRE-FEETeooo r----r----r--,...-----r---r--~__,---r--_r__-....___,

PROS MIN .... M 8T P OS

4000 ~,-+--+--+----t--+--+___+--A--+___l~_l

3000 ~-+---+--+--~--+--+__I_+--f--\-+_____I-~

2000 t--,-+--+--+----+--+---H-~~-+--+-~__l~_l

1000 I---+--+--+---+--+-~-.M-~L---+-~~~~---l

ACTUAL STORAGE 1991 PROJECTED STORAGE 1992

~ PROB ~IN ~MO~T PAC B ~~PRO ~ MAX

) ~~~

J7

( /~---..~'"

I ...........~~ / ~

"""'tl-.::: ~/---ll----..Jj ..........~ ~'""--1!~

12OND JFMAMJ JAS

14

18

1e

20

22

MILLION ACRE-FEET24

r~""'""'1!~ '---E ~~~""--e

~~ "---;]

20

18

14

22

18

12OND JFMAMJ JAS

MILLION ACRE-FEET24

14

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I I

LOWER BASIN RESERVOIRS

LAKE MEAD(COLORADO RIVER)

Water Year 1991

'II

At the beginning ofwater year 1991, Lake Mead, impoundedby Hoover Dam, had a water surface elevation of 1180 feetand an active storage of 20,144,000 acre-feet. During thewinter months, the water level gradually declined to about1178 by early January, and rose to about 1180 feet by the endof March 1991 and then gradually declined to 1176 feet nearthe end of May 1991. During the period June throughSeptember, Lake Mead continued to drop, reaching a lowelewtion ofabout 1173 feet during the last weekofSeptember,with a corresponding active storage of 18,694,800 acre-feet.

During the water year, releases were made to meetdownstream water use requirements in the United States andMexico, programmed levels ofLake Mohave and Havasu, andnet transit losses which include river and reservoirevaporation, uses by phreatophytes, changes in bank storage,unmeasured inflows, and diversions to the Las Vegas, Newda

area via the Robert B. Griffith Water Project (Project). Thetotal release from Lake Mead through Hoover Dam duringthe water year 1991 was approximately8,961,000 acre-feet. Allof the amount passed through the turbines for powerproduction.

In addition, 267,000 acre-feet were diverted from Lake Meadby the Project. At the end of the water year, Lake Mead hada water surface elevation of 1173 feet and an active of19,233,000 acre-feet which reflects a decrease in storageduring the water year of 911,000 acre-feet. On September 30,1990, the active storage ofLake Mead was 4,534,000 acre-feetgreater than the active storage in Lake Powell.

ACTUAL RELEASES 1991 LAKE MEAD

122911231083

162,700 Acres115 Miles

Acre-feet Elewtion, feet

27,377,00013,653,00010,024,000

Reservoir

Powerplant

Storage CapacityRated HeadMinimum PowerSurface Area, fullReservoir Length, full

J

/ ~~ ~"-/

!i--"~ ~J

)~

[~V '\~(

1000

800

600

THOUSAND ACRE-FEET1200

400

200

oOND JFMAMJJAS

Number of UnitsTotal Capacity

171,952,500 KW

15

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Water Year 1992 MOST PROBABLE RELEASES 1992

j/~~ !t---E~~

['-. V \J~~~V

800

800

400

THOUSAND ACRE-FEET1200

1000

Under most probable inflow conditions during the 1992water}'ear, the Lake Mead water level is expected to be drawn downto elevation 1164 feet at the end ofAugust 1992. At that level,the lake will have in active storage approximately 18.2 millionacre-feet. During water year 1992, a total of approximately8.96 tnillion acre-feet is scheduled to be released from LakeMead under most probable conditions, all passing through thepowerplant.

0

0

/ '" ) ~~J0

/ ~~ /(

-r/ ~~v-

a

a

a

o

MOST PROBABLE REGULATED INFLOW 1992

THOUSAND ACRE-FEET

200

20

80

80

40

120

100

The outlook for lowest and highest monthly releases of 1992will be about 500,000 acre-feet and 1,000,000 acre-feet,respectively. Drawdown, during the peak large mouth bassspawning period in April and May, is expected to be withinthe limits ofdecline recommended in a July 1982 report. Thatreport summarized results of a 5 year study by the ArizonaGame and Fish Department and the Nevada Department ofWildlife and recommended a drawdown rate of less than 2inches per day.

ACTUAL STORAGE 1991 MOST PROBABLE STORAGE 1992

2

2

2

MILLION ACRE-FEET

/ ~~~~ '"[a---e'\~~

21

18o N D J F M A M J J A S

18

20

MILLION ACRE-FEET222

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8

81OND JFMAMJ JAS

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LAKE MOHAVE(COLORADO RIVER)

Water Year 1991

At the beginning of water year 1991, the water surfaceelevation ofLake Mohave, which is impounded byDavis Dam,was 632.9 feet, with an active storage of approximately1,431,000 acre-feet.

During the winter months, after some fluctuation, the welterlevel was gradually raised to approximately 645 feet, with anactive storage ofapproximately 1,760,000 acre-feet by the endof March 1991. The water level was then lowered during theApril through Mayperiod. The reservoir declined to elevation639 feet during the latter part of June 1991. During July andAugust, Lake Mohave gradually lowered further to anelevation of 635 feet, with an active storage of approximately1,487,000 acre-feet, in the middle of August. Lake Mohavefluctuated around the elevations of 635 and 636 feet duringAugust through mid-September then gradually rose to an

elevation of 638 feet by the end of September. The reservoirended the water year at an elevation of 638.3 feet, with1,571,400 acre-feet in active storage.

Lake Mohave releases were made for downstream water userequirements, including diversions by users in the vicinities ofLaughlin, Nevada; Bullhead City, Arizona; and Needles,California, by The Metropolitan Water District of SouthernCalifornia (MWD), the Central Arizona Project (CAP), andthe users downstream from Parker Dam. During the wateryear, total releases of approximately 8,377,000 acre-feet weremade at Davis Dam, all of which passed through the turbinesfor power production. Of that amount, approximately1,253,000 acre-feet were then pumped from Lake Havasu byMWD, and 473,000 acre-feet were pumped for the CAP.

ACTUAL RELEASES 1991 LAKE MOHAVE

THOUSAND ACRE-FEET

Elevation, feet

647623570

28,200 Acres67 Miles

5240,OOOKW

1,810,0001,188,000

217,500

Acre-feetReservoir

Storage CapacityRated HeadMinimum PowerSurface Area, fullReservoir Length, full

Powerplant

Number of UnitsTotal Capacity

0

0..;~

)~~V ~\

0

V \D)

'T'\~~ / V0 ., !t"

0

60

120

20

100

80

oONDJFMAMJ JAS

40

17

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MOST PROBABLE RELEASES 1992

THOUSAND ACRE-FEET0

0./~

~ "t/~

\0 J! \0_r

-~~~

/(0 ., ~ .

0

0

20

40

80

80

100

120

Water Year 1992

Both Lake Mohave and Lake Havasu are scheduled to bedrawn down in the winter months to provide storage space forlocalstorm runoffand will be filled in the spring to meet highersummer water needs. This drawdown will also correspondwith maintenance at both Davis and Parker Powerplantswhich is scheduled for September through December. Thenormal filling pattern of these two reservoirs coincides wellwith the fishery spawning period. Since lake elevations will besimilar to previous years, relatively normal conditions areexpected for boating and other recreational uses.

.J::J

/ ~ ~~~\[il

J! \J~~'-

V~

MOST PROBABLE REGULATED INFLOW 1992

400

800

800

THOUSAND ACRE-FEET1200

1000

Under most probable inflowcondition, the water level ofLakeMohave is scheduled to reach an elevation of about 643 feetby the end ofFebruary 1992 and then remain at that elevationuntil the end of May. The reservoir will gradually drop to anelevation of approximately 630 feet by the end of the wateryear. During the water year a total of 9.0 million acre-feet isscheduled to be released from Lake Mohave to meet alldownstream requirements. All of that total is scheduled topass through the powerplant.

200

o

ACTUAL STORAGE 1991 MOST PROBABLE STORAGE 1992

0

0/ "~

~~ '\_/VI.

\0

~,0

~J

0

THOUSAND ACRE-FEET180

1200ONDJFMAMJ JAS

150

180

170

140

130

V \V

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(.,...-.( ""1~

1800

1~OO

1700

1600

1200o N D J F M A M J J A S

1300

THOUSAND ACRE-FEET1800

18

Page 22: OPERATION OF THE COLORADO RIVER BASIN 1991 · PDF fileOPERATION OF THE COLORADO RIVER BASIN 1991 ... Basin Project Act of1968 Public Law90-537. ... 6506 6491 6485 8,058 Acres 18 Miles

LAKE HAVASU(COLORADO RIVER)

Water Year 1991

At the beginning of water year 1991, the water level of LakeHavasu, impounded by Parker Dam, was at an elevation ofabout 447 feet with an active storage ofapproximately 560,000acre-feet. During October and November 1989, the reservoirfluctuated between elevations 446 feet and 447 feet. ByMarch1990, the reservoir was at an approximate elevation of446 feetto provide vacant space for runoff from the drainage areabetween Davis and Parker Dams. The water level was thenraised to an elevation of450 feet by the middle ofMay with anactive storage of about 610,000 acre-feet. At the end of thewater year, Lake Havasu was at an elevation ofabout 447 feetwith an active storage of 556,000 acre-feet.

During the water year, approximately6,867,000 acre-feet werereleased at Parker Dam, all of which passed through the

turbines for power production. In addition to the releasesfrom Parker Dam, approximately 1,253,000 acre-feet werediverted from Lake Havasu by The Metropolitan WaterDistrict ofSouthern California. Diversions from Lake Havasufor the Central Arizona Project were 473,000 acre-feet duringthe water year.

Space in the top 10 feet of Lake Havasu (about 180,000acre-feet) is reserved bythe United States for controloffloodsand other uses, including river regulation. Normally, onlyabout the top 4 feet, or 77,000 acre-feet of space, have beenused for this purpose since the Alamo Reservoir on the BillWilliams River has been in operation.

ACTUAL RELEASES 1991 LAKE HAVASU

Elevation, feet

450450440

20,400 Acres35 Miles

619,400619,400439,400

Acre-feetReservoir

Powerplant

Storage CapacityRated HeadMinimum PowerSurface Area, fullReservoir Length, full

/'-.

/ ~~,.

~\j/~

)~

(~

')r---t

~(

800

THOUSAND ACRE-FEET1000

400

200

800

oONDJFMAMJ JAS

Number of UnitsTotal Capacity

4120,OOOKW

19

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MOST PROBABLE RELEASES 1992

./\.

V~~(' \

~,v "r~

C\)~~V

.0

200

400

600

800

THOUSAND ACRE-FEET1000

Water Year 1992

Lake Havasu is scheduled at the highest levels consistent withthe requirements for maintaining reservoir regulation space.A yearly low elevation of approximately 446 feet is scheduledfor October through February to provide storage space forlocal storm runoff. The yearly high of about 450 feet isscheduled in the spring to meet higher summer water needs.During water year 1992, a total of approximately 7.0 millionacre-feet is scheduled to be released from Lake Havasu tomeet all downstream requirements. All of that amount isscheduled to pass through the Parker Powerplant.

MOST PROBABLE REGULATED INFLOW 1992

THOUSAND ACRE-FEET0

0 / '"[;;l....".. ..........-l!~ ~\/ ---t!r

0 J( )]-fJ

u'"~~ /1(0 ..,

~

0

0

20

80

60

40

120

100

ACTUAL STORAGE 1991 MOST PROBABLE STORAGE 1992

THOUSAND ACRE-FEET THOUSAND ACRE-FEET85

55

60

0

0~~,

~/~ ~~~D

~~ ......... '-.

~~~

0

0

0

45

85

60

50

40ONDJFMAMJ JAS

0

0~~ ---'~

V ""'t!~ ~~~J_r ::L...--....I:

-~ r~

0

0

50

400ONDJFMAMJ JAS

20

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River Regulation

The runoff into Lake Powell for water year 1991 continued tobe well belownormal for the fourth straight year. Unregulatedinflow into Lake Powell was 71 percent of normal for wateryear 1991. Unregulated inflows for water years 1988, 1989 and1990 were 70 percent of normal, 54 percent of normal and 46percent of normal respectively. Upper Basin reservoirs,.Flaming Gorge, Blue Mesa, and Navajo, experienced modestrebounds in storage in water year 1991. These increases instorage occurred because releases from these reservoirs wereprimarily constrained to minimum levels. Storage in LakePowell and Lake Mead, however, is down significantly. TheOctober 1, 1991, vacant space in these two reservoirs wasapproximately 17.8 million acre-feet. This vacant space hasresulted from three successive years of low inflow and therequirement to maintain the minimum deliveries to meetobligations pursuant to 'The Law of the River".

DaHy releases are provided from the storage reservoirs in theLower Basin to meet the needs ofwater user agencies, for riverregulation, and as needed for flood control. When possible,all water passes through the powerplant units. The dailyreleases are regulated on an hourly basis to balance the powerneeds of the hydroelectric power customers, the flow needs ofendangered species of fish and recreational needs. Atappropriate locations, minimum instream flow objectiveshave been established, which preserve the present aquaticresources downstream of certain Colorado River dams. Inmany cases, these resources were poor or nonexistent prior tothe time of dam construction, and the subsequent minimum,cool water releases have provided an improved environmentfor aquatic resources and sport fisheries. In general,

21

controlled releases allow for an extended recreation season,and reduce the high flow periods in May and June. Wateryears 1988, 1989, 1990 and 1991 have been dryer than normaland a return to more normal reservoir inflow levels in futureyears will provide increased benefits to fish, wildlife andrecreation uses.

Operational <?bjectives at and below Laguna Dam are toconserve water, control sediment, and maintain the riverchannel. Storage ofwater above Laguna Dam in the reservoir,in surcharge, and in bankstorage provides for controlled flowsin the river at Yuma. When combined with seepage anddrainage, this storage allows a continuous live stream servingrecreational and fish and wildlife purposes. On a fewoccasions each year, higher daily flows below Laguna, causedby rainstorms or user rejected water orders, are used tomaintain sufficient river channel capacity through flushing ofsediment. This occasional practice reduces channelmaintenance expense without impairment to waterconservation or power production.

Based on existing reservoir conditions and river regulationoperations below Hoover Dam, the total 1992 delivery toMexico is scheduled to be a treaty delivery of 1,500,000acre-feet for the calendar year. In addition, approximately140,000 acre-feet ofdrainage waters are expected to bypass tothe Gulf of California via the Bypass Drain during calendaryear 1991. This bypass channel was constructed pursuant toprovisions of Minute No. 242 of the International Boundaryand Water Commission.

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Flood Control

Lake Mead is operated in accordance with updated floodcontrol regulations which are specified in the Field WorkingAgreement between Reclamation and the Corps ofEngineers, signed in 1982. The regulations stipulate theminimum release le·vels needed from Lake Mead to route thereasonable maximum inflow. The reasonable maximum inflowis the estimated inflowvolume that, on the average, will not beexceeded 19 out of20 times. This volume is derived by addingan "uncertainty"term to the most probable runoffforecast. In1983, unusual hydrometeorological events resulted inunprecedented large forecasting errors. Subsequentreassessment of the estimate of the ''uncertainty'' term led toadoption of larger values for use in determining thereasonable maximum inflow in 1984 and thereafter.

No flood control releases are scheduled for 1992, but in futureyears, as Lake Mead refills and flood control releases areagain required by the Hoover Dam Flood ControlRegulations, consideration will be given to making thosereleases over the fall and winter months to avoid high flowrates during the January to July runoff season. Thisdistribution of water reduces the chance of bypassinghydroelectric powerplants below Hoover Dam and avoids the

22

adverse impacts of higher flood control releases on fish andwildlife, recreation, water quality, and river stabilization.

Routine maintenance of bankline protection facilities werecarried out during water year 1991. As in the previous years,greater than normal bankline repair was necessitated in partby increased wave action from boating and other recreationalriver traffic. During water year 1991, the river channel in theLower Basin has remained in good balance, neither aggradingnor degrading significantly in any particular reach.

Total Colorado River reservoir system storage at the start ofwater year 1991 was approximately 43.9 million acre-feet andabout 42.2 million acre-feet at the end of the water year,representing a 1.7 million acre-foot increase in total remainingavailable reservoir space.

Alamo Dam on the Bill Williams River (in the Lower Basin)received minor flood inflow during water year 1991. Duringwater year 1992, Painted Rock (Gila River) and AlamoReservoirs are scheduled to be operated in accordance withestablished flood control criteria to maximize the availableflood control space in their respective reservoirs.

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Beneficial Consumptive Uses

An extensive discussion of consumptive uses is treated indetail in Reclamation·s "Colorado River SystemConsumptive Uses and Losses Report, 1981-1985." Thisreport is prepa~ed jointly by the Upper and Lower ColoradoRegional Offices. The report presents estimates of theconsumptive uses and losses from the Colorado River Systemfor each year from 1981 through 1985. The table on thefollowing page was created using the data from theConsumptive Uses and Losses Report (June 1991). The tablesummarizes annual water use from the system by States,including water use supplied by ground-water overdraft. The1986-1990 report, is expected to be awilable in 1992.

Upper Basin Uses and Losses

The three largest categories of consumptive use and losses inthe Upper Colorado River Basin are agricultural uses withinthe basin, transbasin diversions to adjacent drainages, andevaporation losses from the major reservoirs. Estimatedevaporation losses were about 591,000 acre-feet from UpperBasin reservoirs in water year 1991. In water year 1990,746,244 acre-feet were diverted for use in adjacent drainages.The total for transbasin diversions in water year 1991 has notyet been tabulated but the figure is expected to be similar tothe 1990 total.

Lo~rBasin Uses and Losses in the United States

During water year 1991, an estimated 5.5 million acre-feet ofwater were released from Lake Havasu (Parker Dam) to meetthe requirements for water deliveries at Imperial Dam, as wellas those of the Colorado River Indian Reserwtion nearParker, Arizona, the Palo Verde Irrigation District nearBlythe, California, other miscellaneous users along the river,and transit losses between Parker Dam and Imperial Dam.

The major water diversions above Parker Dam were by TheMetropolitan Water District (MWD) of Southern Californiaand the Central Arizona Project (CAP). MWD pumpedapproximately 1,253,000 acre-feet from Lake Havasu duringwater year 1991, and approximately 473,000 acre-feet werepumped for the CAP.

23

Releases of approximately 8.4 million acre-feet were madefrom Lake Mohave during water year 1991, to provide forreleases to meet minimum downstream needs in the UnitedStates at Parker Dam; to supply diversion requirements ofMWD and CAP, miscellaneous contractors, and other users;to offset evaporation and other transit losses between Davisand Parker dams; and to maintain the scheduled levels ofLake·Havasu.

During water year 1991, releases ofapproximately 8.9 millionacre-feet were made from Lake Mead at Hoover Dam. Thesereleases regulate the levels of Lake Mohave, provide for thesmall users on that reservoir, and provide for releases at DavisDam to meet needs in the United States as well as deliveriesto Mexico. In addition, 270,000 acre-feet were diverted fromLake Mead for use by the Lake Mead National RecreationArea; Boulder City; Basic Management, Inc.; and contractorsof the Colorado River Commission of Nevada. Of thediversions from Lake Mead, approximately 160,000 acre-feetwere consumptivelyused and the remainder returned to LakeMead. Total releases and diversions from Lake Mead duringwater year 1991 were an estimated 9,200,000 acre-feet.

For water year 1992, a total release of 7.0 million acre-feetfrom Lake Hawsu is projected, including consumptive use'requirements in the United States below Parker Dam, transitlosses and regulation in the river between Parker Dam and theMexican Border, and treaty deliveries to Mexico.

Based on studies made in October 1991, it is expected thatMWD will divert 1,300,000 acre-feet by pumping from LakeHavasu during water year 1992. Similarly, the CAP is expectedto pump approximately 645,000 acre-feet. These figures maychange as the water year progresses. Consumptive uses bysmall users, river losses or gains, and reservoir losses betweenDavis Dam and Parker Dam are projected to be a net loss of66,000 acre-feet.

There are no major users between Hoover Dam and DavisDam. During water year 1992, diversions from Lake Mead areprojected at 308,000 acre-feet. Ewporation from Lake Meadis projected to be about 820,000 acre-feet and net gainbetween Olen Canyon Dam and Lake Mead is expected to beabout 820,000 acre-feet.

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Water Use by States and Water Passing to MexicoWater use by states, basins, and tributaries1

( 1,000 acre-feet)

AverageState 1981 1982 1983 1984 1985 1981-85

Arizona 6,167 5,143 4,237 5,041 4,838 5,085California 4,839 4,349 3,953 4,679 4,710 4,506Colorado ... 2,086 2,106 1~920 1,865 1,994 1,994Nevada 350 352 339 355 373 354New Mexico .. 342 425 425 417 401 402Utah ... 782 746 718 762 879 777Wyoming 341 330 346 307 336 332Other2

.• 1,598 1,403 1,896 1,197 1,783 1,575TotalColorado River Basin 16,505 14,854 13,834 14,623 15,314 15,025

Water Passing to MexicoTreaty ...... 1,751 1,495 1,646 1,694 1,671 1,652Minute 242 ... 131 146 166 138 131 142Excess Releases 2,115 176 7,970 15,160 11,594 7,403TotalWater Passing to Mexico . 3,997 1,817 9,782 16,992 13,396 9,197

Total- Colorado RiverSystem and WaterPassing to Mexico ..... 20,502 16,671 23,616 31,615 28,710 24,222

NOTE:IThe above states' uses are onsite consumptive uses and losses and include water uses satisfied byfoundwater overdrafts.Represents main stem reservoir evaporation in the Upper Basin and main stem reservoir evaporation

and channel loss below Lee Ferry in the Lower Basin.

Source - "Colorado River System Consumptive Uses and Losses Report, 1981-1985 (June 1991)"

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Power Operations and Major Maintenance Activities

Upper Basin - Colorado River Storage Project

During water year 1991, work was performed to uprate Unit1 at Flaming q.orge. Unit 1 at Morrow Point and Unit 2 atFlaming Gorge are, scheduled for uprating during water year1992. Seal rings on Unit 3 at Glen Canyon are also scheduledto be replaced in water year 1992.

The following table summarizes CRSP generation, purchases,disposition, and revenues from power operations for fiscalyear 1991, and present projections for fIScal year 1992. Abreakdown by percent of power sources, disposition, andrevenues for the fiscal year is shown on the opposite page. Thetotal gross revenue from power operations in fiscal year 1991was $96,249,052.

CRSP Power Generation

Water Year 1991

Sources of Energy Kilowatt-hours Revenue DollarsNet Generation Firm Power Sales $ 84,237,761

Blue Mesa 234,907,000 Non Firm Power SalesCrystal 142,117,000 EmergencyFlaming Gorge 303,363,000 Fuel ReplacementFontenelle 61,758,000 (Oil ConserVcltion) 4,699,771Glen Canyon 3,634,447,000 Reserve Capacity 0Morrow Point 287,812,000 Parker-Davis Project

Sub-total- Firming 0Net Generation 4,664,404,000 Transmission Service 7,059,790

Rental of Substation Facilities 187,562Miscellaneous Revenue 64,168

Miscellaneous Kilowatt-hoursPurchases 1,486,000,000 Total Gross Revenue $ 96,249,052Interchange Receipts 450,000,000Energy Charges

to Transmission Water Year 1992Service Customers 19,596,000

(Projected) Kilowatt-hoursSub-total-Miscellaneous 1,955,596,000 Estimated Firm Energy Sales 5,733,587,000Total Energy From Estimated Nonfttm Sales 200,000,000

All Sources 6,620,000,000 Estimated Purchases 1,367,783,000Estimated Peaking

Disposition of Energy Kilowatt-hours Capacity Sales (Per Month)Firm Energy Sales 5,538,235,000 Winter 1991-92 0Nonfirm Energy Sales Summer 1992 0

EmergencyFuel Replacement Estimated Revenue $ 115,545,782(Oil Conservation) 278,891,000

Interchange Deliveries 171,120,000System Losses 631,754,000

Total Energy Distributed 6,620,000,000

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Colorado River Storage Project PO\\er Operations

(Water Year 1991)

Energy Sources

Energy Disposition

Revenue

Glen Canyon &~S

Transmission Service 1S~~~ZX'5~oo(X;~Fontenell. 1'1

Crystal 2.

Blue Uesa 341

Flaming Gorge es

Interchange Receipts 7'1

Interchange Deliveries 3'1

Nonflrm Salee 4S

System Lossee gS

MI8ceilaneous 1.Nonflrm Sales 5~

Transmleslon Service 741

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Power Operations [Cont.]

Lower Basin

Water Year 1991

On June 1, 1987, the United States assumed operation andmaintenance responsibility of Hoover Powerplant andassociated switching stations, after the 5O-year contract withoperating agents (The CityofLos Angeles and its Departmentof Water and Power, and Southern California EdisonCompany, Ltd.) expired. The HOeneral Regulations forGeneration and Sale of Power in Accordance with theBoulder Canyon Project Adjustment ActH

, promulgated onMay 20, 1941, provided the basis for computation of chargesfor elect~ical energy generated at Hoover Dam through May31, 1987. The Department of Energy Organizational Act of1977 transferred the responsibility for the power marketingand transmission functions of the Boulder Canyon Projectfrom the Bureau of Reclamation (Reclamation) to theWestern Area Powcr Administration (Western). The powermarketing functions ofWestern include the responsibility forpromulgating charges for the sale ofpowcr. The construction,power generation, operation, maintenance, and replacementresponsibilities associated with the Hoover Powerplant andappu~tenantworks remained with Reclamation.

Marketing of Parker-Davis power and operating thetransmission system are the responsibility of Western.Reclamation continues to operate and maintain the dams andtheir po-werplants, a function of the Lower Colorado DamsProject Office.

Davis and Parker Powerplants continue to be operated byremote control from Western's SupervisoryControl and DataAcquisition (SCADA) computer system located at theirPhoenix Area Office. The SCADA system monitors andremotely controls the powerplant generating units to adhereto water schedules provided by Reclamation·s waterscheduling branch located at the Lower Colorado DamsProject, Hoover Dam. Routine maintenance was performedat Davis and Parker powerplants.

The total 'energy delivered to the Hoover contractors duringthe 1991 fiscalyear (October 1, 1990 through September 30,1991) was 3,986,719,000 kilowatt-hours. Of that amount, theSchedule A contractor received 3,313,211,000 kilowatt-hoursand the Schedule B contractor received 673,508,000kilowatt-hours. Schedule C contractor received no deliveriesin the 1991 operating year.

In water year 1991, one generating unit, A9, at HooverPowerplant was uprated. This increased the usable capacityby8.5 megawatts and brought the total plant capacityto 1952.5megawatts. Of the 17 generating units at Hoover powerplant,13 have been uprated.

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Four generating units remain to be uprated. Unit A8 is in theprocess ofbeing uprated and is scheduled to be completed inFebruary, 1992. Unit A3 is in the process ofbeing uprated andis scheduled to be completed in May, 1992. Unit A4 isscheduled for completion in November, 1992. Unit N8 isscheduled for completion in December, 1992. The totalHoover powerplant capacity, at the completion ofuprating, isestimated to be a maximum of 2,074 megawatts. Principalwork under the contract includes conducting a study of eachexisting generator's design, furnishing and installing necessarynew components, and modifying the generators, as required,to accomplish the proposed uprating. The. objective is touprate the generators bythe optimum amount, based on wateravailability and economic feasibility. Studies show thatsufficient water, head, and turbine capacity are available toproduce significantly more generator output than the existinggenerator ratings will allow.

Water Year 1992

In operation studies of Lake Mead and Lake Powell for theoperating year which ends September 30, 1992, the amountsreleased at Hoover Dam have been projected to satisfy bothdownstream water requirements, including diversions byTheMetropolitan Water District and the Central Arizona Project,while also complying with the overall requirements to meetCompact, flood control, and operating criteria releaseprovisions. The water scheduled to be released will generateSchedules A and B energy. The estimated monthly Hooverreleases during water year 1992 total 8.96 million acre-feet. Itis estimated that generation from these Hoover releases willresult in delivery to the approved contractors ofapproximately 4.1 billion kilowatt-hours of electrical energy.

Normal routine maintenance at Hoover Powerplant has beenscheduled around the uprating program outages, and uponcompletion of the uprating program in December of 1992,maintenance will return to a more normal schedule. The fourmain penstocks are scheduled for inspection and repairduring the next 2 years.

The Hoover Uprating Program was authorized by the HooverPowerplant Act of 1984 (ACT), which finalized an historicthree-State agreement on the marketing of Hoover powerafter the original contracts terminated on May 31, 1987. TheAct also requires that the Hoover Uprating Program beundertaken with funds advanced by the non-Federalpurchasers of Hoover power.