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<br />
<br />Field inspection for Safety E....aluation 01 Exishng Dams,
<br />
<br />provided a substantial increase to the
<br />snowpack with 44 new records established
<br />on May 1, and on May 7 the forecast was
<br />increased back up to 13 maf. This
<br />forecasted runoff volume together with the
<br />uncertainty of the spillway repair schedule
<br />required that the river outlet works at Glen
<br />Canyon be opel1ed.
<br />
<br />Temperatures remained cool during the first
<br />half of May with precipitation below normal
<br />over the Green River and San Juan Basins
<br />and near normal over the Upper Colorado
<br />River drainage. A late snow melt similar
<br />to 1983 conditions occurred once again with
<br />very-worm-temperatures about mid.May.
<br />Streamflow jumped dramatically with the
<br />unregulated inflow above lake Powell
<br />going from 40,(K)() cubic feet per second
<br />(cis) on May 9 to 126,000 cis on May 19.
<br />
<br />By May 24, it was obvious that with the
<br />remaining snow, additional runoff was
<br />likely, and therefore the forecasted inflow
<br />for April through July was increased to 14.0
<br />maf, 188 percent of normal. The daily
<br />peak for the season at lees Ferry occurred
<br />on May 28 at 148,000 cis, compared to the
<br />peak of 128,CX>O cfs on June 2, 1983.
<br />The record peak flow at lees Ferry was
<br />220,000 cis in 1921.
<br />
<br />
<br />Inspeclion of Hoover Dam's ,Nevada spillway tunnel.
<br />
<br />By June 7, 1984, the runoff forecast had
<br />increased to 14.2 maf Or 190 percent of
<br />normal, which required that Glen Canyon's
<br />river outlet works and powerplant releases
<br />remain at maximum capacity. The runoff
<br />forecast was again increased on July 6,
<br />1984, to 15.2 maf which was 204 percent of
<br />normal. The actual April through July 1984
<br />inflow to lake Powell was 15,258,000 acre-
<br />feet, which was 446,000 acre.feet higher
<br />than the April through July 1983 amount.
<br />Lake Powell itself peaked at elevation
<br />3,702.46 on July 8, 1984, almost 2.5 feet
<br />into surcharge. The river outlet works
<br />were gradually reduced and eventually
<br />closed by_July 23,1984._
<br />
<br />The pattern of heavy fall precipitation and
<br />record January 1, 1984, snowpacks in the
<br />Upper Basin, in retrospect, was favorable
<br />for the lower Basin since it led to the
<br />highest January 1 forecast ever mode. This
<br />in turn required flood control releases in
<br />excess of 30,000 cfs from Hoover Dam. At
<br />the time, these seemed to be extremely
<br />high releases based on such an early
<br />forecast. However, the high early releases
<br />proved to be an important factor in
<br />Reclamation's control of the runoff in 1984.
<br />
<br />
<br />23.millionln visitor at Hoover Dam,
<br />
<br />The actual water supply in the Colorado
<br />River Basin for all of water yeor 1984 was
<br />179 percent of normal, ranging from 228
<br />percent of normal on the mainstem
<br />Colorado River above Grand Junction,
<br />Colorado, to 167 percent of normal on the
<br />Gunnison River above Blue Mesa Dam to
<br />111 percent of normal on the San Juan
<br />River above Navajo Dam. The total
<br />unregulated inflow to Lake Powell for
<br />water year 1984 was 21.253,000 acre.feet
<br />which exceeded the total 1983 water year
<br />inflow by 700,000 acre-feet. The total
<br />release from Glen Canyon Dam for the
<br />entire water year was 21,051,000
<br />. acre.leet._ .Aggregate .Colorado River
<br />storage at the ~nd of the water year was
<br />57,344,000 acre.feet representing a
<br />decrease of 1,618,000 acre.feet from the
<br />previous year. By the end of the water
<br />year, active storage in the system was
<br />approximately 102 percent of the January
<br />maximum available storage. This
<br />"maximum available storage" represents
<br />storage at all Bureau of Reclamation and
<br />Colorado River Storage Project (CRSP)
<br />reservoirs, including lake Havasu and other
<br />upstream reservoirs. Flood control
<br />regulations require a minimum of 5,350,000
<br />acre.feet of vacant space in the system on
<br />January 1.
<br />
<br />o
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