Current Dam Operations

 

 

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Update 2/9/12 Glen Canyon Dam / Lake Powell –In January 2012 the unregulated inflow volume to
Lake Powell was 356 kaf (99% of average). This volume is very close to the final
forecast for January issued by the Colorado Basin River Forecast Center on January 5th
which was 375 kaf. The elevation of Lake Powell on January 31st, 2012 was 3636.90 feet
above sea level (63.10 feet below full pool). During January, the elevation of Lake
Powell decreased by 3.52 feet and it is likely that the elevation will continue to decrease
near this rate for approximately 2 more months. By late March or early April, when the
snowpack begins to melt, inflows will likely increase to a point where they are greater
than releases and the elevation will begin to rise. Snowpack conditions above Lake
Powell are 77% of average as of February 8, 2012.
The current Water Supply forecast (April through July Unregulated Inflow Volume) for
Lake Powell for 2012 is 5.05 maf which is 71% of average. Based on this inflow
forecast, it is currently projected that the most probable annual release from Glen Canyon
Dam in water year 2012 will be 9.46 maf. At this time of year however, there is a high
level of uncertainty in hydrologic forecasts and the annual release volume from Glen
Canyon Dam in WY2012 will ultimately be based on the actual inflows that occur during
2012 rather than this Water Supply forecast.
Current Dam Operations
In August 2011, pursuant to the Interim Guidelines, the Operating Tier for Glen Canyon
Dam was established to be the Equalization Tier. Under the Equalization Tier for 2012,
with 1.233 maf of release carried over from 2011 to 2012, the annual release volume for
2012 could be as low as 9.46 maf or higher depending on actual inflow conditions. As
hydrologic conditions for Lake Powell and Lake Mead change throughout the year,
Reclamation will adjust operations of Glen Canyon Dam to release the appropriate annual
volume during 2012 to achieve Equalization objectives as practicably as possible by
September 30, 2012.
Releases from Glen Canyon Dam are currently averaging about 12,500 cfs with
fluctuations for power generation throughout the day that peak near 13,000 cfs in the
afternoons and with early morning low level releases are about 7,000 cfs. This operation
is consistent with the Glen Canyon Operating Criteria (Federal Register, Volume 62, No.
41, March 3, 1997). The release volume for February is scheduled to be 650 kaf. In
March, the monthly release volume will likely be 600 kaf and fluctuating releases from
Glen Canyon Dam will likely average about 10,100 cfs each day with scheduled daily
fluctuations occurring within the range from 7,000 cfs to 13,000 cfs.
In addition to daily scheduled fluctuations for power generation, the instantaneous
releases from Glen Canyon Dam may also fluctuate to provide 40 MW of system
regulation. These instantaneous release adjustments stabilize the electrical generation
and transmission system and translate to a range of about 1100 cfs above or below the
hourly scheduled release rate. Typically, fluctuations for system regulation are very short
lived and balance out over the hour and do not have noticeable impacts on downstream
river flow conditions.
Releases from Glen Canyon Dam can also fluctuate beyond scheduled fluctuations for
power generation when called upon as a partner that shares reserve requirements within
the electrical generator community (i.e. balancing area). There are many generators that
supply electricity to the transmission system within the balancing area. At times, a
participating generator may experience operating conditions such that it cannot make its
scheduled delivery of electricity to the system (i.e. unscheduled outage). To provide
system reliability, all participating electricity generators within the balancing area
maintain a specified level of generation capacity (i.e. reserves) that can be called upon
when an unscheduled outage occurs. Glen Canyon Dam typically maintains 113 MW of
reserves for this purpose.
Reserve agreements allow the controllers of the balancing area to call upon Glen Canyon
Dam to produce up to an additional 113 MW of electricity beyond what is originally
scheduled for a given hour. Reserve calls can be maintained for a maximum of 2 hours
after which time the generation rate should be returned to the original schedule. The 113
MW reserve requirement for Glen Canyon Dam translates to approximately 2,800 cfs of
flow in the river. When the balancing area controllers call for reserve generation from
Glen Canyon Dam, releases from the dam can exceed scheduled levels and have a
noticeable impact on the river downstream from Glen Canyon Dam. But these calls for
reserves are fairly infrequent and typically are for much less than the required level of
113 MW.
Current Inflow Forecasts and Model Projections
Over the next three months (February, March and April) the forecasted unregulated
inflow volume to Lake Powell is projected to be 390 kaf (99% of average), 550 kaf (83%
of average) and 800 kaf (76% of average), respectively. These percent of averages are all
based on the historic period from 1981 through 2010. Combining this forecast with the
February Water Supply Forecast and extending projections to the end of WY2012, the
most probable (i.e. 50% likely to be exceeded) unregulated inflow volume for WY2012 is
projected to be 8.48 maf (78% of average). There is significant uncertainty associated
with this forecast. Recent analysis indicates that it is reasonably possible for the actual
unregulated inflow volume to be as low as 5.48 maf (51% of average) or as high as 12.65
maf (117% of average) depending on the range of precipitation patterns that could occur
over the next several months.
Based on the reasonable range inflow conditions that could occur this year, the annual
release volume from Glen Canyon Dam could be as low as 9.46 maf to as high as 12.92
maf. Under the most probable inflow condition, the annual release volume is projected
to be 9.46 maf and the elevation of Lake Powell at the end of WY2012 is projected to be
3643.2 feet above sea level. This elevation corresponds to a live storage volume of 16.38
maf (67% of full capacity).
Upper Colorado River Basin Hydrology
Since water year 2005, hydrologic conditions in the Upper Colorado River Basin have
been near average with significant variability from year to year. The unregulated inflow
to Lake Powell, which is a good measure of the hydrologic condition in the Colorado
River Basin, has averaged 10.98 maf (101% of average (period 1981-2010)) per year
during the period from 2005 through 2011. The hydrologic variability during this period
has been from a low water year unregulated inflow of 8.62 maf (80% of average) in water
year 2006 to a high of 15.97 maf (147% of average) which occurred in water year 2011.
Overall reservoir storage in the Colorado River Basin has increased by nearly 10 maf
since the beginning of water year 2005 and this is a significant improvement over the
drought conditions during water years 2000 through 2004. On October 1, 2004, the
beginning of water year 2005, the total reservoir storage in the Colorado River Basin was
29.84 maf (50.2% of capacity). As of January 30, 2012 the total reservoir storage in the
Colorado River Basin was 38.35 maf (64.3% of capacity).
Updated: February 9, 2012
Rick Clayton

 

1/23/12The purpose of this notification is to confirm that the release volume from Glen Canyon Dam for February 2012 will be 650,000 acre-feet. Hourly and daily average releases from Glen Canyon Dam for February 2012 will be scheduled through Western Area Power Administration to be consistent with the Glen Canyon Dam Operating Criteria (Federal Register, Volume 62, No. 41, March 3, 1997) and to also achieve, as nearly as is practicable, this monthly volume.

Hourly releases during February 2012 are anticipated to peak in the afternoon to approximately 13,000 cfs with early morning hourly low releases of approximately 7,000 cfs.

We anticipate the release volume for March 2012 will be 600,000 acre-feet. This will be confirmed in a subsequent notification toward the end of February.

This notification supersedes all previously issued notifications and is current until a new notification is issued. All times identified in this notification are local time (Mountain Standard Time) and not hour ending.

Glen Canyon Dam / Lake Powell –During December 2011 the unregulated inflow
volume to Lake Powell was 359 kaf (99% of average based on the historic period from
1981 through 2010). This was well below the volume forecasted for the month of
December which was 500 kaf (138% of average). As a result, the elevation of Lake
Powell at the end of December was 3639.7 feet above sea level which was 1.1 feet lower
than projected at the beginning of December.
Snowpack conditions above Lake Powell are well below average for this time of year.
As of January 9, 2012 the overall snowpack above Lake Powell was only 60% of
average. Reclamation has received the first Water Supply forecast for 2012 and the April
through July unregulated inflow to Lake Powell is projected to be 5.05 maf which is 71%
of average. Based on this forecast, the projected most probable (i.e. 50% likely to be
exceeded) annual release volume from Glen Canyon Dam in water year 2012 will be 9.46
maf. At this time of year however, there is a high level of uncertainty in hydrologic
forecasts and the annual release volume from Glen Canyon Dam in WY2012 will
ultimately be based on actual hydrology rather than forecasted hydrology.
Current Dam Operations
In August 2011, as part of the Colorado River Annual Operating Plan process, the
Operating Tier for Glen Canyon Dam was determined to be the Equalization Tier under
the 2008 Interim Guidelines. Under the Equalization Tier, with 1.233 maf of release
volume carried over from 2011 to 2012, the annual release volume for WY2012 could be
as low as 9.46 maf to as high as 13.1 maf or higher depending on actual inflow
conditions. As inflow and storage conditions for Lake Powell and Lake Mead change
throughout the year, Reclamation will make practicable adjustments to the operation of
Glen Canyon Dam to release the appropriate annual volume during 2012. The overall
goal during 2012 in terms of annual release will be to achieve the objectives of the
Equalization Tier of the Interim Guidelines.
In response to the Water Supply forecast issued for Lake Powell in January, Reclamation
has reduced the release volume for January from 1000 kaf to 850 kaf. This reduction
began on January 10, 2012. Releases from Glen Canyon Dam are currently averaging
about 13,200 cfs with fluctuations for power generation throughout the day that peak near
17,500 cfs in the afternoons. Early morning low releases are about 9,500 cfs. This
operation is consistent with the Glen Canyon Operating Criteria (Federal Register,
Volume 62, No. 41, March 3, 1997).
In addition to hourly release fluctuations for load following power generation, the
instantaneous releases from Glen Canyon Dam may also fluctuate somewhat to provide
40 MW of system regulation. These instantaneous release adjustments stabilize the
electrical generation and transmission system and translate to a range of about 1100 cfs
above or below the hourly release rate that is scheduled for a given hour. Typically,
fluctuations for system regulation are very short lived and balance out over the hour and
do not have noticeable impacts on river flow conditions.
Releases from Glen Canyon Dam can also fluctuate beyond the typical load following
pattern when called upon as a partner that shares reserve requirements within the
electrical generator community (i.e. control area). There are many generators that supply
electricity to the transmission system within the control area. At times, a participating
generator may experience operating conditions such that it cannot make its scheduled
delivery of electricity to the system (i.e. outage). To provide system reliability, all
participating electricity generators within the control area maintain a specified level of
generation capacity (i.e. reserves) that can be called upon when an outage occurs. Glen
Canyon Dam typically maintains 109 MW of reserves for this purpose.
Reserve agreements allow the controllers of the transmission system to call upon Glen
Canyon Dam for up to 109 MW of additional generation beyond what is originally
scheduled for a given hour. These calls for reserve generation can be maintained for up
to 2 hours in total duration. The 109 MW reserve requirement for Glen Canyon Dam
translates to approximately 2,700 cfs of flow in the river and calls for reserves can have
noticeable impacts on river flow conditions. Calls for reserves are fairly infrequent and
typically are for much less than the maximum requirement of 109 MW.
Current Inflow Forecasts and Model Projections
Over the next three months (January, February, March) the forecasted unregulated inflow
volume to Lake Powell is projected to be 375 kaf (104% of average), 410 kaf (104% of
average) and 575 kaf (86% of average), respectively. These percent of averages are all
based on the historic period from 1981 through 2010. Combining this forecast with the
January Water Supply Forecast and extending projections to the end of WY2012, the
most probable (i.e. 50% likely to be exceeded) unregulated inflow volume for WY2012 is
now projected to be 8.55 maf (79% of average). The minimum probable (i.e. 90% likely
to be exceeded) unregulated inflow volume for WY2012 is now projected to be 5.48 maf
(51% of average). The maximum probable (i.e. 10% likely to be exceeded) unregulated
inflow volume for WY2012 is now projected to be 12.65 maf (117% of average).
Based on this range of possible inflow conditions, the January 24-Month Study projects
the annual release volume for WY2012 to be as lows as 9.46 maf (under the minimum
probable inflow condition) to as high as 13.01 maf (under the maximum probable inflow
condition). Under the most probable inflow condition, the annual release volume is
projected to be 9.46 maf and the elevation of Lake Powell at the end of WY2012 is
projected to be 3643.9 feet above sea level. This elevation corresponds to a live storage
volume of 16.47 maf (68% of full capacity).
Upper Colorado River Basin Hydrology
Since water year 2005, hydrologic conditions in the Upper Colorado River Basin have
been near average with significant variability from year to year. The unregulated inflow
to Lake Powell, which is a good measure of the hydrologic condition in the Colorado
River Basin, has averaged 10.98 maf (101% of average (period 1981-2010) per year
during the period from 2005 through 2011. The hydrologic variability during this period
has been from a low water year unregulated inflow of 8.62 maf (80% of average) in water
year 2006 to a high of 15.97 maf (147% of average) which occurred in water year 2011.
Overall reservoir storage in the Colorado River Basin has increased by nearly 10 maf
since the beginning of water year 2005 and this is a significant improvement over the
drought conditions during water years 2000 through 2004. On October 1, 2004, the
beginning of water year 2005, the total reservoir storage in the Colorado River Basin was
29.84 maf (50.2% of capacity). As of January 10, 2012 the total reservoir storage in the
Colorado River Basin was 38.54 maf (64.8% of capacity).
Updated: January 11, 2012
Rick Clayton