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What is do not exceed water level to have larger lake at end of year

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bubba

Well-Known Member
So what is the do not exceed water level to maintain a larger Powell, basically is there a water surface elevation point that if exceeded would actually result in lake Powell going to a lower level at the end of the year with more water going to Mead? Is the water going to Mead a percentage of total of what Powell gets each year or a stepped fixed amount, if fixed then it sounds like Powell would stay bigger by keeping just below that point to have a higher elevation at end of annual cycle. Is this a fair game or would Powell dump excess water to Mead early (if less than additional requirement amount) to stay below that level. On the flip side would the powers manipulate the levels by holding water to barely hit that level resulting in a larger release if fixed. Is there a priority lake? Does Mead split the loses to seeping and evaporation at Powell or do they get a full wet share with Powell absorbing all natural losses. Regardless, more water the better and good for Mead to be raising too.
 

birdsnest

Well-Known Member
I used to get a kick thinking about the people that pee in Powell sending it to Vegas until I moved there. The questions asked here are really good and will take someone who really is hooked into the water system.
 

Gem Morris

Well-Known Member
Basically you're asking at what point does "equalization" kick in? Waterbaby answered that question in a post about 2 weeks ago...
 

Gem Morris

Well-Known Member
They decide in advance what the total release will be which may or may not include a "flush" for the Grand Canyon then release that pre-decided amount in varying rates depending on power generation requirements and the "flush" requirement (the "flush" is included in the total release).
 

wayne gustaveson

Moderator
Staff member
The water level established a few years ago was 3640. If Lake Powell is at that level in September then more water is released downstream. I have not had a USBR update lately so I am not sure if this is still in effect. Does anyone know for sure what the current regulations are?
 

Waterbaby

Moderator
Staff member
The last update May 11th said they are going to release 9.0 this year - that there is a 10% chance they will only release 8.23... see below....

(Last Updated: May 11, 2017
)

Current Status

The unregulated inflow volume to Lake Powell in April was 1,607 thousand acre-feet (kaf) (152 percent of average). The release volume from Glen Canyon Dam in April was 621 kaf. The end of April elevation and storage of Lake Powell were 3,604 ft (96 feet from full pool) and 12.15 maf (50% of full capacity), respectively. The reservoir reached a seasonal low elevation on March 15th near elevation 3593.85 feet. Since that time the reservoir has been increasing as the first of the spring runoff is now entering the reservoir.

Current Operations

The operating tier for water year 2017 was established in August 2016 as the Upper Elevation Balancing Tier. The April 2017 24-Month Study established that Lake Powell operations will be governed by balancing for the remainder of water year 2017. Under balancing, the contents of Lake Powell and Lake Mead will be balanced by the end of the water year, but not more than 9.0 maf and not less than 8.23 maf shall be released from Lake Powell. Based on the most probable inflow forecast, this May 24-Month Study projects a balancing release of 9.0 maf in water year 2017; the actual release in water year 2017, however, will depend on hydrology in the remainder of water year and will range from 8.23 to 9.0 maf. The projected release from Lake Powell in water year 2017 will be updated each month throughout the remainder of the water year. Reclamation will schedule operations at Glen Canyon Dam to achieve as practicably as possible the appropriate total annual release volume by September 30, 2017.


As determined in the August 2016 24-Month Study, and documented in the 2017 Annual Operating Plan, Lake Powell’s operations in water year 2017 will be governed by the Upper Elevation Balancing Tier. Starting with an 8.23 million acre-feet (maf) release from Lake Powell in water year 2017, the April 2017 24-Month Study projected the end of water year elevation at Lake Powell to be above 3,575 feet and the end of water year elevation at Lake Mead to be below 1,075 feet. Therefore, in accordance with Section 6.B.4 of the Interim Guidelines, Lake Powell operations shifted to balancing releases for the remainder of water year 2017. Under balancing, the contents of Lake Powell and Lake Mead will be balanced by the end of the water year, but not more than 9.0 maf and not less than 8.23 maf shall be released from Lake Powell.


Based on the May most probable inflow forecast, the annual release volume from Lake Powell during water year 2017 is projected to be 9.0 maf. Under the minimum probable inflow scenario, the water year release is projected to be 9.0 maf. Under the maximum probable inflow scenario, the release is projected to be 9.0 maf. There is 10% chance that inflows will be lower than the current minimum probable forecast, potentially resulting in lower releases. If inflows are less than the minimum probable forecast, the water year 2017 annual release could be as low as 8.23 maf. If inflows are greater than the current forecasted maximum probable inflow, the annual release will be 9.0 maf.
The projected release from Lake Powell in water year 2017 will be updated each month throughout the remainder of the water year.

Based on the current forecast, the May 24-Month Study projects Lake Powell elevation will end water year 2017 near 3,638 feet with approximately 15.72 maf in storage (65% capacity). Projections of elevation and storage still have significant uncertainty at this point in the season, primarily due to uncertainty regarding spring runoff and the resulting inflow to Lake Powell. Under the minimum probable inflow scenario, updated in April, the projected end of water year elevation and storage are 3,625 feet and 14.25 maf (59% capacity), respectively. Under the maximum probable inflow scenario, updated in April, the projected end of water year elevation and storage are 3661 feet and 18.62 maf (77% capacity), respectively. Modeling of projected reservoir operations based on the minimum and maximum scenarios will be updated again in August.
Upper Colorado River Basin Hydrology

The Upper Colorado River Basin regularly experiences significant year to year hydrologic variability. During the 17-year period 2000 to 2016, however, the unregulated inflow to Lake Powell, which is a good measure of hydrologic conditions in the Colorado River Basin, was above average in only 3 out of the past 17 years. The period 2000-2016 is the lowest 17-year period since the closure of Glen Canyon Dam in 1963, with an average unregulated inflow of 8.57 maf, or 79% of the 30-year average (1981-2010). (For comparison, the 1981-2010 total water year average is 10.83 maf.) The unregulated inflow during the 2000-2016 period has ranged from a low of 2.64 maf (24% of average) in water year 2002 to a high of 15.97 maf (147% of average) in water year 2011. In water year 2016 unregulated inflow volume to Lake Powell was 9.62 maf (89% of average), which, though still below average, was significantly higher than inflows observed in 2012 and 2013 (45% and 47% of average, respectively). Under the current most probable forecast, the total water year 2017 unregulated inflow to Lake Powell is projected to be 12.93 maf (119% of average).

At the beginning of water year 2017, total system storage in the Colorado River Basin was 30.2 maf (51% of 59.6 maf total system capacity). This is nearly the same as the total storage at the beginning of water years 2015 and 2016 which began at 30.1 maf and 30.3 maf, respectively, both of which were 51% of capacity. Since the beginning of water year 2000, total Colorado Basin storage has experienced year to year increases and decreases in response to wet and dry hydrology, ranging from a high of 94% of capacity at the beginning of 2000 to a low of 50% of capacity at the beginning of water year 2005. One wet year can significantly increase total system reservoir storage, just as persistent dry years can draw down the system storage. Based on current inflow forecasts, the current projected end of water year total Colorado Basin reservoir storage for water year 2017 is approximately 33.8 maf (57% of total system capacity). The actual end of water year 2017 system storage may vary from this projection, primarily due to uncertainty regarding the season’s snowpack and resulting runoff and reservoir inflow. Based on the April minimum and maximum probable inflow forecasts and modeling, the range of end of water year 2017 total system capacity is approximately 32.47 maf (54%) to 37.0 maf (62%), respectively.
 

Waterbaby

Moderator
Staff member
So in a nutshell. In order for Powell to 'fill', Meade will have to 'fill'. Confusing.

Pretty much and to fill Mead then we have to have a once-in-a-hundred years runoff that would require them to let a LOT of water out of Powell to make room for the runoff.
 

TheMarinator

Well-Known Member
Then how was Powell ever full ? Was there different rules back then , or was there several good water years and then 84 just topped it off ?

It seems like under these new rules it will take several monster water years and that will only fill mead and not even help Powell .
 

Waterbaby

Moderator
Staff member
Then how was Powell ever full ? Was there different rules back then , or was there several good water years and then 84 just topped it off ?

It seems like under these new rules it will take several monster water years and that will only fill mead and not even help Powell .

Pretty much true, it will take one or more of the 100-year-storms to fill both lakes.

They have both gone up and down since forever, though... with the drought/wet cycles. People forget we were in a substantial drought back in the late 70's and all the lakes were lower - then with the big flood of 1983 everything filled to capacity - it was followed by another very wet year and for the most part Powell held in the 3690's and slowly dropped into the 80's until this drought cycle started in 2002. When there is a lot of snow in the AZ mountains and in SW Utah Lake Mead benefits - but with the drought both have been relatively dry in the winter months so Mead has been forced to depend of releases from Lake Powell rather than the 8.23 from Powell -

The rivers feeding Mead in addition to Lake Powell is:

Virgin
Muddy
Paria River
The Little Colorado [drains into the Colorado in the Grand Canyon - water comes from melting snow and storms in the AZ White Mountains

In addition there is a lot of creeks and washes that drain into the Colorado and into Mead - they carry water into the lake during rain storms.

There was some talk of building a pipeline from Northern Nevada to Lake Mead. Of course the powers that be in Vegas love that idea - the residents of Northern Nevada do not. I understand they are recycling water in Vegas and sending it back to Mead.... not sure I want to think about that since I'm a down-streamer.
 

Dale

Well-Known Member
But, WB, doesn't your recycled water go into the CAP to Phoenix? Hmmm, we pee in Powell and everyone downstream recycles theirs. Don't think I will be drinking the water in Phoenix anymore!
 
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