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<br />Lake Powell [Colorado River]
<br />
<br />Water V..r 1983
<br />During water year 1983, Lake Powell, whloh Is
<br />impounded by Gren Canyon Dam, was
<br />operated as part at the CASP In accords.nce
<br />wIth govern\ng contracts and laws to provIde
<br />river regulation, optimum power production,
<br />recreation, and fIsh and wIldlife
<br />enhancement.
<br />
<br />On September 30, 1982, the Lake Powell water
<br />surface elevation was 3,687 feet wIth 8n active
<br />content of 23,005,000 acre-feel. The water
<br />surface elevation was gradually drawn down
<br />to a low of 3,682 feet prior to the s.prlng !'Ui\oH.
<br />
<br />An unusual and unpredictable combination of
<br />below normal May tern paratures and heavy
<br />late spring storms followed rapidly by much
<br />above nOlmal temperatures horn \a's May
<br />through mld.June and heavy basin-wide rains
<br />resulted In a near record-breakIng April
<br />through July runoff In the Colorado River
<br />above Lake Powell. The April through July
<br />Inllow to Lake Powell was 14.5 million
<br />acre-feet, about 190 percent of the long-term
<br />average, and the highest Inflow for that period
<br />since the 1920 record of 14.7 million acre-feet.
<br />Runoff above lake Powell for all of water year
<br />1983 totaled 20.5 million acre-faet,
<br />approxImately 180 percent of average,
<br />
<br />With this near record Inflow, the Lake Powell
<br />water su~(e.ce e.lel.laUQr. rose past \\a norma\
<br />maximum of 3,700 faet to a high 013708.34
<br />feet on July 14, 1983.
<br />
<br />As the water surface rose above 3,700 feet, the
<br />How 01 wa\erthrough Glen Canyon Dam's
<br />spillway began to cause damage to the
<br />concrete lining of the spillways. To reduce the
<br />flow of water through the splllweys, 8-foot
<br />high reinforced steel extensions were placed
<br />on the spillway gates. The placement of the
<br />spillway gate extensions also reduced the
<br />release of water to Lake Mead by permitting
<br />the safe storage of almost 1 .4 million acre-feet
<br />In the reservoir'S surcharge pool. The
<br />Jperatlon of the reservoir was effective In
<br />'educing the peak Inflow of approximately
<br />116,000 cfs to a maximum dally release of
<br />12,800 cfs nearthe end of June 1983. The
<br />o\al release of water from Lake Powell during
<br />'later year 1983 was approximately 17 ,4
<br />nllllon acre-feet, with 3.6 million acre--feet
<br />IYP88slng the powerplant. Powerplant
<br />Iypas! began on June 2,1983, and continued
<br />
<br />14
<br />
<br />
<br />Lake Powl!llIand Glen Canyon Dam from ...rsllor'e center.
<br />
<br />through Auguatll ,1983. By the end of the
<br />water year, the active storage In Lake Powell
<br />was 24,817 ,000 acre-Ieet at elevation 3,699
<br />leet.
<br />
<br />Watar Year 1984
<br />
<br />The water year 1984 plan of operation for Lake
<br />Powell has been developed In response to
<br />scheduled spillway repaIr work necessitated
<br />by the damage caused by the high flows In
<br />1983. The plan Is to draw the water surface
<br />elevation down suffIciently to enable the
<br />reservoir to handle a heavy runoff volume as
<br />experlencad In 1983, without requlrlng-
<br />spillway flows, To draw the reservoir down to
<br />approximately elevation 3673 feet, prior to
<br />the spring runoff, powerplant capacity
<br />releases of approximately 25,000 cfs are
<br />scheduled through March 1984. Beginning
<br />April 1 , 1984, releases wilt be based on the
<br />April through July volume runoff forecast
<br />reflecting the current hydrologIc conditions.
<br />
<br />Assuming average runoff conditIons.
<br />scheduled releases from Lak.e Powell will be
<br />14.5 million acre-feet. lIthe runoff Is In the
<br />lower quartile, the releases are expected to be
<br />at least 11.6 million aCfe--feet. WI\h an upper
<br />quar\lle or greater Inflow, the releases from
<br />Lake Powell will likely exceed 15.6 million
<br />acre-feet. With an upper decile Inflow, It will
<br />be necessary to bypass the power plant.
<br />
<br />. ,
<br />
<br />Lake Powell Active Storage"
<br />Reservoir (Acre-Feet)
<br />
<br />Maximum Storage
<br />Rated Head
<br />Minimum Power
<br />Surface Area (Full)
<br />Reservoir Length
<br />(Full)
<br />
<br />Power Plant
<br />Number of Units
<br />Total Capacity
<br />
<br />Chart 5
<br />
<br />EI.
<br />(Ft.)
<br />
<br />25,002,000 3700
<br />9,428,000 3570
<br />4,126,000 3490
<br />161,390 Acres
<br />
<br />186 Miles
<br />
<br />8
<br />1,021,000 Kilowatts
<br />
<br />"does r'lot Include 1,998,000 acre-Ieel 01 dead
<br />storage below 3370 f881
<br />
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