Updates
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Glen Canyon Monthly Operational Call
The DOI also will conduct monthly Glen Canyon Dam operational coordination meetings or calls with the DOI bureaus (USGS, NPS, FWS, BIA, and Reclamation), WAPA, AZGFD, and representatives from the Basin States and the UCRC. Each DOI bureau will provide updates on the status of resources and dam operations. In addition, WAPA will provide updates on the status of the Basin Fund, projected purchase power prices, and its financial and operational considerations. These meetings or calls are intended to provide an opportunity for participants to share and obtain the most up-to-date information on dam operational considerations and the status of resources (including ecological, cultural, Tribal, recreation, and the Basin Fund). One liaison from each Basin State and from the UCRC will be allowed to participate in the monthly operational coordination meetings or calls. [1]
The slide decks for these calls can be found to the right on this page under Presentations and Papers.
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Critical Reservoir Elevations at Powell and Mead
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The back of Glen Canyon Dam as Lake Powell was filling showing the 8 penstocks on the right and the two river outlet works on the left.
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The Relationship Between Reclamation and Western Regarding Operating Glen Canyon
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Reclamation’s Upper Colorado Region Water Office makes monthly water release schedules in acre-feet for Glen Canyon based upon anticipated inflows to the lake, release requirements to the lower basin and storage targets for the lake. This monthly water schedule is passed on to Western’s Resource Scheduling Office in Montrose, CO. Western’s scheduling office then develops an hourly release schedule. This schedule takes into account Glen Canyon ROD requirements and the requirements and agreements made by Western and Reclamation regarding the operation of the other CRSP powerplants. Western’s dispatch office in Phoenix, Arizona then provides Reclamation’s Glen Canyon Power Operations Center with a daily, 24 hour operating schedule, identifying Western’s desired hourly electric power schedule (in megawatts). This schedule is then put into the computer system at Glen Canyon by Reclamation (2). This schedule then becomes the megawatt quantities which are targeted during the “real time” operation at Glen Canyon Dam.
The Glen Canyon Power Operations Center operators utilize the generation schedule supplied by Western to operate the generating units while giving consideration to efficiency and equipment characteristics. In addition, the generators automatically respond to a “regulation signal” developed and electronically transmitted to the dam by Western for continuous response to power system load and frequency changes. (This is further described later in this paper). [2]
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Recent History of the "Flexibility" Within Operation Constraints
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Shortly after Interim Flows began (August , 1991), Western met with staff at the Glen Canyon Environmental Studies (GCES) and with other Reclamation representatives. Western requested flexibility in order to regulate an electrical control area. This resulted in an agreement whereby Western was allowed to fluctuate 10% around any operational constraint and that Western would meet with GCES staff monthly to discuss any operational issues that surfaced. Thus, the Interim Flow downramp requirement of 1,500 cfs could be as high as 1,650 cfs and still be in compliance (1,500 cfs + 150 cfs).
After the ROD and Operating Criteria were signed, Western and Reclamation negotiated a MOU to more fully detail operational issues. Reclamation was interested in changing the 10% band width because it believed that the ROD and Operating Criteria didn’t specify that kind of flexibility. Instead, Western was allowed to use up to 1,000 cfs for regulation purposes. Compliance was to be monitored by SCADA using a one hour integrated value. It was thought that, even though a downramp at any one moment of time could be as high as 2,500 cfs (1,500 cfs + 1,000 cfs), it would be uncommon for the downramp to exceed 1,500 cfs since this is recorded as an integrated value over the hour. [3]
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Emergency Exception Criteria vs the Regulation of an Electrical Control Area
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The EIS identified Emergency Exception Criteria as common elements in all alternatives. They are defined in the EIS as follows (3):
“Normal operations described under any alternative would be altered temporarily to respond to emergencies. NERC has established guidelines for the emergency operations of interconnected power systems. . . . Examples of system emergencies include:
- Insufficient generating capacity
- Transmission system: overload, voltage control, and frequency
- System restoration
- Humanitarian situations (search and rescue)”
When emergency exception criteria are invoked, normal operations are suspended until the emergency has ended, or Western has discharged its North American Energy Reliability Council (NERC) responsibility regarding the emergency. Emergency exception criteria are further defined in the operating criteria and in the MOU on Glen Canyon operations signed by Western and Reclamation.
It was the invocation of emergency exception criteria on April 1st, 1998 which piqued the interest of some AMWG members in Reclamation and Western’s interpretation of the ROD.[4]
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Emergency Exception Criteria vs. Regulation
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Both emergency exception criteria and regulation have been described in this paper. Recently, some members of the AMWG and TWG have focused their concerns and discussion on “emergencies”. However, the issue at hand and the subject of this paper is regulation. It is largely regulation that has resulted in the occasional exceedence of the 1,500 cfs downramp.[5]
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Policy Conclusions by Reclamation and Western
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It does not seem reasonable that the ROD was intended to require either: 1) the exclusion of Glen Canyon Dam from participating in regulating a load control area, or 2) participation in regulating a load control area but limiting hourly load following to 500 cfs downramp (or something like it). Further, the environmental impact of regulation appears to be minimal, based on a review of the flows at the Lee Ferry gage. Finally, it has become clear to Reclamation and Western that precise and inviolate control of water releases from Glen Canyon Dam is beyond the capabilities of the machinery and electronic controls. For these reasons, Reclamation and Western intend to impose the following changes:
- Limit scheduled down ramps to 1,450 cfs (rather than 1,500),
- Employ the use of SCADA table in the preparation of Western’s hourly schedules,
- Investigate the transfer of a portion of the “ACE” to other CRSP powerplants,
- Move the ACE signal back to Glen Canyon Dam (i.e. return “regulation” to the dam) once it has been demonstrated that the ACE will not cause “routine” excedences,
- Work with the AMWG to determine the proper level of analysis required to address the potential downstream impacts of regulation in Glen and Grand Canyons,
- Educate all interested parties on the power system and equipment operations and the associated results to water releases at the dam,
- Add release data to Western’s web site and provide periodic reports to the TWG on the operation of Glen Canyon Dam and,
- Continue efforts to for better coordination between Reclamation and Western regarding the scheduling and operation of Glen Canyon Dam.[6]
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The Law of the River [7]
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The Colorado River is managed and operated under numerous compacts, federal laws, court decisions and decrees, contracts, and regulatory guidelines collectively known as the "Law of the River." This collection of documents apportions the water and regulates the use and management of the Colorado River among the seven basin states and Mexico. Following is a synopsis of the most significant documents:
- The Colorado River Basin Project Act of 1968 - This Act authorized construction of a number of water development projects in both the upper and lower basins, including the Central Arizona Project (CAP). It also made the priority of the CAP water supply subordinate to California's apportionment in times of shortage, and directed the Secretary to prepare, in consultation with the Colorado River Basin states, long-range operating criteria for the Colorado River reservoir system.
- The Arizona v. California U.S. Supreme Court Decision of 1964 - In 1963, the Supreme Court issued a decision settling a 25-year-old dispute between Arizona and California. The dispute stemmed from Arizona's desire to build the Central Arizona Project so it could use its full Colorado River apportionment. California objected and argued that Arizona's use of water from the Gila River, a Colorado River tributary, constituted use of its Colorado River apportionment, and that it had developed a historical use of some of Arizona's apportionment, which, under the doctrine of prior appropriation, precluded Arizona from developing the project. The Supreme Court rejected California's arguments, ruling that lower basin states have a right to appropriate and use tributary flows before the tributary co-mingles with the Colorado River, and that the doctrine of prior appropriation did not apply to apportionments in the lower basin. In 1964, the Court issued its decree. This decree enjoined the Secretary of the Interior from delivering water outside the framework of apportionments defined by the law and mandated the preparation of annual reports documenting the uses of water in the three lower basin states. In 1979, the Supreme Court issued a Supplemental Decree which addressed present perfected rights referred to in the Colorado River Compact and in the Boulder Canyon Project Act. These rights are entitlements essentially established under state law, and have priority over later contract entitlements.
- Colorado River Storage Project of 1956 - Provided a comprehensive Upper Basin-wide water resource development plan and authorized the construction of Glen Canyon, Flaming Gorge, Navajo and Curecanti dams for river regulation and power production, as well as several projects for irrigation and other uses.
- Upper Colorado River Basin Compact of 1948 - Created the Upper Colorado River Commission and apportioned the Upper Basin's 7.5 maf among Colorado (51.75 percent), New Mexico (11.25 percent), Utah (23 percent), and Wyoming (14 percent); the portion of Arizona that lies within the Upper Colorado Basin was also apportioned 50,000 acre-feet annually.
- California Seven Party Agreement of 1931 - This agreement helped settle the long-standing conflict between California agricultural and municipal interests over Colorado River water priorities. The seven principal claimants - Palo Verde Irrigation District, Yuma Project, Imperial Irrigation District, Coachella Valley Irrigation District, Metropolitan Water District, and the City and County of San Diego - reached consensus in the amounts of water to be allocated on an annual basis to each entity. Although the agreement did not resolve all priority issues, these regulations were also incorporated in the major California water delivery contracts.
- The Boulder Canyon Project Act of 1928 - This act: (1) ratified the 1922 Compact; (2) authorized the construction of Hoover Dam and related irrigation facilities in the lower Basin; (3) apportioned the lower basin's 7.5 maf among the states of Arizona (2.8 maf), California (4.4 maf) and Nevada (0.3 maf); and (4) authorized and directed the Secretary of the Interior to function as the sole contracting authority for Colorado River water use in the lower basin.
- The Colorado River Compact of 1922 - The cornerstone of the "Law of the River", this Compact was negotiated by the seven Colorado River Basin states and the federal government in 1922. It defined the relationship between the upper basin states, where most of the river's water supply originates, and the lower basin states, where most of the water demands were developing. At the time, the upper basin states were concerned that plans for Hoover Dam and other water development projects in the lower basin would, under the Western water law doctrine of prior appropriation, deprive them of their ability to use the river's flows in the future. The states could not agree on how the waters of the Colorado River Basin should be allocated among them, so the Secretary of Commerce Herbert Hoover suggested the basin be divided into an upper and lower half, with each basin having the right to develop and use 7.5 million acre-feet (maf) of river water annually. This approach reserved water for future upper basin development and allowed planning and development in the lower basin to proceed.
There are several other laws, contracts and document which are part of the "Law of the River" in addition to these provisions, the federal Endangered Species Act and various Native American water claim settlements both affect the extent to which water developments and diversions can be utilized in the Colorado River Basin.
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Links and Information
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Presentations and Papers
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2026
2025
2024
2023
2022
2021
2020
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How to Calculate Monthly Volumes
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First: allocate 2.0 MAF to October - December:
- Divide October, November, and December according to proportions determined by the Contract Rate of Demand (CROD) for power produced at Glen Canyon Dam
- October receives 642,584 AF or 32.13% of the 2.0 MAF
- November receives 641,532 AF or 32.08% of the 2.0 MAF
- December receives 715,885 AF or 35.79% of the 2.0 MAF
Then allocate the remaining annual release according to CROD proportions:
- Jan 12.25%
- Feb 10.83%
- Mar 11.44%
- Apr 10.20%
- May 10.15%
- Jun 10.65%
- Jul 12.02%
- Aug 12.84%
- Sept 9.63%
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How to Calculate a Daily Hydrograph
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Determine the Monthly Volume:
Calculate the Daily Fluctuation Factor:
- June, July, and August: 10% of the Monthly Volume (in cfs)
- All others: 9% of the Monthly Volume (in cfs)
Determine the Allowable Daily Fluctuation (cfs):
- Multiply the Monthly Volume by the Daily Fluctuation Factor
Determine the Number of Days in the month:
Calculate the Daily Volume (acre feet):
- Divide the Monthly Volume by the Number of Days in the month
Calculate the Mean Daily Discharge (cfs):
- Multiply the Daily Volume by 43560.000627
- Divide by 86400
Calculate the Base Flow (cfs):
- Divide the Allowable Daily Fluctuation by 2
- Subtract this number from the Mean Daily Discharge
Calculate the Peak Flow (cfs):
- Divide the Allowable Daily Fluctuation by 2
- Add this number from the Mean Daily Discharge
Calculate the number of Hours on Peak:
- Takes some sort of solver program (GTMax) to construct a hydrograph that maximizes the number of hours on peak with the available Daily Volume
Calculate the timing of Hours on Peak:
- Takes some sort of optimization program (GTMax) that schedules releases when electrical power has the most value
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What are the minimum monthly volumes while still staying within the ROD daily minimum releases of 5,000 and 8,000 cfs?
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| Month
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Minimum Monthly Volume (af)
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| January |
400,950 |
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| February |
362,149 |
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| March |
400,950 |
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| April |
388,017 |
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| May |
400,950 |
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| June |
388,017 |
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| July |
400,950 |
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| August |
400,950 |
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| September |
388,017 |
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| October |
400,950 |
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| November |
388,017 |
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| December |
400,950 |
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| Total |
4,720,868 |
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Operations under MLFF [8]
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Minimum flows:
- 8,000 cfs between 7 a.m. and 7 p.m.
- 5,000 cfs between 7 p.m. and 7 a.m.
Maximum non-experimental flows:
Daily range:
- 5,000 for monthly volumes <600 kaf
- 6,000 for monthly volumes 600– 800 kaf
- 8,000 for monthly volumes >800 kaf
Ramp rates:
- 4,000 cfs/hr up
- 1,500 cfs/hr down
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Other Stuff
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How much water can be released at Glen Canyon Dam?
- 8 generators = 4,000 cfs each = 32,000 cfs
- 4 bypass tubes = 3,750 cfs each = 15,000 cfs
- 2 spillways = up to 208,000 cfs [9]
As reservoir elevations decline, lower pressure (head) pushes less water through the penstocks and bypass tubes.
Critical water elevations
- 3715' = dam crest elevation
- 3700' = top of spillway gates (3704' with plywood flashboards)
- 3648' = spillway crest elevation
- 3490' = minimum power pool (to prevent cavitation in the penstocks)
- 3470' = penstock elevation (this is the centerline elevation, the penstocks are 15' in diameter)
- 3374' = bypass tube elevation (this is the centerline elevation, the bypass tubes are 8' in diameter)
- 3370' = reservoir deadpool elevation [10]
How fast do water and waves flow down the Grand Canyon?
Discharge waves move downstream faster than the water. For example, in May 1991, the discharge waves produced by rapidly changing dam releases moved through the canyon in about 1 2/3 days, whereas the water took about 4 1/3 days to travel the 235 miles from Lees Ferry to Gneiss Canyon (RM 235.7).
Video of the construction of Glen Canyon Dam
1983 flood videos and spillway repairs
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