Grand Canyon Flows to be cut Way Back - Mountain Buzz
 



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Old 08-19-2013   #1
 
Tom Martin's Avatar
 
Flagstaff, Arizona
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Grand Canyon Flows to be cut Way Back

RRFW Riverwire Glen Canyon Dam Update
August 19, 2013

Current Status

The unregulated inflow volume to Lake Powell in July was 143 thousand acre-feet (kaf) (13% of average). The release volume from Glen Canyon Dam in July was 848 kaf. The end of July elevation and storage of Lake Powell were 3594.2 feet (106 feet from full pool) and 11.20 million acre-feet (maf) (46% of full capacity), respectively. The reservoir elevation peaked in mid-June at 3601.2 ft and is now declining. The elevation will continue to decline through the fall and winter until spring runoff in 2014.

Current Operations

The operating tier for 2013 is the Upper Elevation Balancing Tier, as established in August 2012 and pursuant to the Interim Guidelines. Since the April 2013 projected end of water year elevation at Lake Powell was below the 2013 Equalization Elevation of 3,646.0 feet and the projected end of water year elevation at Lake Mead was above elevation 1,075.0 feet, Section 6.B.1 and 6.B.4 of the Interim Guidelines provide for an annual release volume of 8.23 maf from Lake Powell during water year 2013. Reclamation will schedule operations at Glen Canyon Dam to achieve as practicably as possible an 8.23 maf annual release volume by September 30, 2013.

Releases from Glen Canyon Dam in August are currently averaging approximately 13,000 cfs with daily fluctuations between approximately 9,000 cfs at nighttime and approximately 17,000 cfs during the daytime and consistent with the Glen Canyon Operating Criteria (Federal Register, Volume 62, No. 41, March 3, 1997). The scheduled release volume for August 2013 is 800 kaf.

In September, the release volume will likely be about 600 kaf, with daily fluctuations for hydropower between approximately 7,000 cfs in the nighttime and approximately 13,000 cfs in the daytime. In October, the release volume will likely be about 480 kaf with daily fluctuations between approximately 5,000 cfs and 10,000 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 1,200 cfs above or below the hourly scheduled release rate. Under system normal conditions, fluctuations for regulation are typically short lived and generally balance out over the hour with minimal or no 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). Reserves provide system reliability in the event of an unscheduled outage. Glen Canyon Dam typically maintains 43 MW of reserves (approximately 1,200 cfs). Reserve calls can be maintained for a maximum of 2 hours after which time the generation rate should be returned to the original schedule. If reserves from Glen Canyon Dam are called upon, releases from the dam can exceed scheduled levels and can have a noticeable impact on the river downstream from Glen Canyon Dam. Calls for reserves are fairly infrequent and typically are for much less than 43 MW.

Inflow Forecasts and Model Projections

The hydrologic forecast for Lake Powell, issued by the Colorado Basin River Forecast Center, projects that the most probable (median) unregulated inflow volume for water year 2013 will be 4.33 maf (40% of average based on the period 1981-2010). The water year 2013 forecast decreased from last month, due to significantly below average inflows in July. Based on the current forecast, the August 24-Month study projects Lake Powell elevation will decline approximately 8 feet through August and September and end the water year at 3585.7 feet with 10.4 maf in storage (43% capacity). The annual release volume from Lake Powell during water year 2013 is scheduled to be 8.23 maf. Reclamation will schedule operations at Glen Canyon Dam to achieve as practicably as possible an 8.23 maf annual release volume by September 30, 2013.

The hydrologic forecast for Lake Powell for water year 2014 projects that the most probable (median) unregulated inflow volume will be 8.32 maf (77% of average based on the period 1981-2010). At this early point in the season, there is significant uncertainty regarding next year's water supply. The forecast ranges from a minimum probable (90% exccedence) of 5.0 maf (46% of average) to a maximum probable (10% exceedence) of 15.5 maf (143% of average). There is a 10% chance that inflows could be higher than the maximum probable and a 10% chance they could be lower than the minimum probable.

Consistent with Section 6.C.1 of the Interim Guidelines, if the August 24-Month study projects the January 1, 2014, Lake Powell elevation to be less than 3,575.0 feet and at or above 3,525.0 feet and the Lake Mead elevation to be at or above 1,025.0 feet, the operational tier for Lake Powell in water year 2014 will be the Mid-Elevation Release Tier and the water year release volume from Lake Powell would be 7.48 maf. The August 2013 24-Month study projects that, with an 8.23 maf annual release pattern in water year 2014, the January 1, 2014, Lake Powell elevation would be 3,573.69 feet and the Lake Mead elevation would be 1,107.39 feet. Therefore, consistent with Section 6.C.1 of the Interim Guidelines, the Lake Powell operational tier for water year 2014 is the Mid-Elevation Release Tier with an annual release volume of 7.48 maf. This determination will be documented in the 2014 AOP, which is currently in the final stages of development.

Upper Colorado River Basin Hydrology

Since 2005 the Upper Colorado River Basin has experienced significant year to year hydrologic variability. During the period 2005 through 2012, the unregulated inflow to Lake Powell, which is a good measure of hydrologic conditions in the Colorado River Basin, averaged a water year volume of
10.22 maf (94% of average (period 1981-2010)). The unregulated inflow has ranged from a low of 4.91 maf (45% of average) in water year 2012 to a high of 15.97 maf (147% of average) in water year 2011. This has been an improvement over the persistent drought conditions of 2000 to 2004, which averaged a water year unregulated inflow of 5.73 maf. However, based on observed inflows and current forecasts, water year 2013 unregulated inflow is expected to be 4.33 maf (40% of average), which would be a second significantly below-average year in a row. If this occurs, the period 2000-2013 would be the driest 14-year period on record with an average annual unregulated inflow of 8.20 maf per year. (For comparison, the standard 1981-2010 period average is 10.83 maf).

At the beginning of water year 2013, total system storage in the Colorado River Basin was 33.9 maf (57 % of capacity), which was an increase of about 4 maf since water year 2005 which began at 29.8 maf (50% of capacity). Since 2005, however, total Colorado Basin storage has experienced year to year increases and decreases in response to wet and dry hydrology. In addition, conditions in both 2012 and 2013 have been significantly drier than average and based on observed inflows and current forecasts, the current projected end of water year 2013 total Colorado Basin reservoir storage is approximately 29.0 maf (49% of capacity).

This update courtesy of Katrina Grantz, Bureau of Reclamation

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Old 08-19-2013   #2
BCJ
 
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Grand Junction, Colorado
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Just an observation, a 10% reduction in flow is what I'm reading, which is not exactly "way back" since the flows at this time of year would ordinarily be far less than they are if nature had its way.
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Old 08-19-2013   #3
 
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Flagstaff, Arizona
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Hi BCJ, You are quite right in that if there was no dam, we would not be doing a Glen Canyon Dam Release notice. But since the dam is still there, I don't see how a 9 to 17k cfs to 5 to 10k cfs is a 10% cutback. It is interesting to note the upper basin will not make it's allotment to the lower basin while Powell reservoir drops to 46% of full capacity. Happy boating, yours, tom
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Old 08-19-2013   #4
BCJ
 
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Hey guys, I'm no "dam defender." But I read this today on Bloomberg: Drought-Induced Curb on Lake Powell Water Is First-Ever - Bloomberg It seems the "whys and whens" are not yet clear, but if they need to hold back 9-10%, that could be done a number of different ways. That was my only point. I have a permit for early-August next year and enjoy the higher water. Have also enjoyed it down around 5K. IF we take out the dam, we'll have to live with nature the way it was intended. That's my point.
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Old 08-19-2013   #5
 
Salida, Colorado
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Based on August, this is about a 20% decrease per month each for Sept and again in Oct. How much of this is seasonal, i.e., reduced electricity demand, and how much does the flow historically drop as we progress from summer into fall? These figures seem consistent with past years, perhaps a bit lower, but I base that on memory, not research.

The telling statement is that the basin is in the driest 14 year period on record. If this continues, it seems only a matter of time until we see flows truly 'cut way back'. I would imagine there is a spillway below the level of the turbine intakes to at least allow for native flow below GCD. Also from memory, weren't the years the original compact was agreed upon one of the wettest time periods on record?
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Old 08-20-2013   #6
 
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The CR Compact was signed in 1922 and allocates 7.5 million acre feet each year to the upper basin and lower basin, divided at Lees Ferry, plus 1.5 M AF to Mexico (of similar quality (read desalinated) water). It requires the upper basin to provide no less than 75 million AF to the lower basin in any 10 year period.

Several studies have estimated the annual flow during the preceding decade was high, and the avg flow is closer to 13-14 M AF per year.
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Old 08-20-2013   #7
 
Salt Lake, Utah
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crazy....i thought colorado had an average year (see "have we peaked yet" thread from may) anyway, with powell dropping about a foot every five to six days a reduction had to be taken sooner or later. The annual release will now be 7.48 rather than 8.23 maf over the year....so yes about a 10% reduction. The ruduced flow for this sep is actually still part of this water year that will come in a 8.23 maf, so that actually is not part of the reduced flows that will take place for the 2014 water year (its about the total water released so seasonalities in flow are common place). One more year like this <4.5 maf inflow and we are going to be really starting down the barrel on the gun, things will get ugly. I'm just hoping dark canyon rapid starts coming back in, how lucky would we be to have that one back! The slit that it lies under should be slowly washing out as we speak.....
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Old 08-20-2013   #8
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Do-Step has a point about power demand, which makes me think I need to wait and see what they do first before drawing too many conclusions. Mid-summer flows could be left where they are for power needs, and the reductions could take place some other time, or they could spread it out, yadayada. Don't know yet.
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Old 08-20-2013   #9
 
cedar city, Utah
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From a long-term trajectory....the "Way Back" remark seems fair. This is a major deal. The first ever cutback in the dams history is emblematic of the larger problems the BOR and states have fundamentally ignored for years, at least in regards to information available to the public. The slideshow here is nothing new but should be scaring the hell out of anybody who lives and/or boats in the west:

Dwindling Colorado River Forces First-Ever Cuts in Lake Powell Water Releases - weather.com

We know we are a stakeholder that is low on the totem pole, plain and simple. At every level of policy our "wants" are principally demoted by the "needs" of others, no matter how arbitrary those distinctions truly are. We are watching as climatologist predictions are being proven time and again to be overly conservative for climate change in this region. This is unprecedented for our and several generations lifetimes.

The politics and greater realities of this are frightening for those of us who live in the region. Those with clout have tried to force municipalities like the one I live in to cap our productive and safe water sources and become reliant on Lake Mead/Powell water that we currently don't use. They are doing this for multiple reasons, all of which are bunk.

So as a boatman I am now faced with multiple issues from the same tangible problem. As a graduate trained in biology I watch as the endangered species I care about are about to be challenged by even greater human caused variables that we were just finally starting to abate.

Yet despite all the tangible and obvious problems I don't have much choice or clout. Places like Denver and the Front Range continue to move water across the Divide; southern California continues to build large scale farms in the desert; Arizona continues to attract millions of retirees to unsustainable metropolises. And everyone of the stakeholders groups I am part of, from small city citizen to rafter, is demoted below the political clout of these decision makers. Decision makers who ignore the realities of the water situation and instead choose to make it worse.

So I am grateful for the occasional honest headline that might help the nation finally accept how screwed up our southwest water systems truly are. Because if they don't remain honest, and we don't support them, then the same type of people who make light of the dead zones in the Mississippi Delta through media will control the narratives our rivers. And the issues of dying cottonwood galleries (an endangered ecosystem of the west) in Deso, camps in the grand, arroyo cutting along most of the Colorado, and boatable flows won't remotely matter.

So cheers to those who occasionally disrupt my own complacency.

Phillip
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Old 08-20-2013   #10
 
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Great discussions. It reminds me that as I am focusing on drought and snow pack, demand for water with new farms and housing developments in the Colorado River watershed keeps on happening. When the BOR as a para or two about new development in the Basin along with the info on reservoir levels and inflow data, we'll know we as a society are serious about water management. What would that para read like? Hmm...

"3,000 new homes and 40,000 acres of new irrigable land were brought on line in the month of August. No new water sources were discovered during this same time period."
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