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Can someone explain what “full pool” means w respect to lake level?


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  • Super User

See pic. Local lake is 402 feet elevation.  Fool pool is 202 feet below that?

 

lake is still low.  I don’t understand.   Is this the level the lake naturally was before the dam was built?
 

 

 

33AAFBF2-3EFD-471A-94FC-A17C186C8442.jpeg

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  • Super User

The legal definition of full pool is:

Full pool elevation means the maximum lake level attained before water releases over a fixed weir, spillway, or other discharge structure. In larger lakes and reservoirs, the full pool elevation is the maximum level established for management.
I looked up one of my reservoirs on that same page you copied and based on its reading, they are basically defining full pool as the normal summer operating level of elevation (rightly or wrongly).
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I read that.  Earlier. 
 

this lake still needs about 40 more feet of water before the open up a north boat ramp. Add how can the water level be 202 feet above where it goes over a spillway?  

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  • Super User

Looks like an error on your lake with their reading…more like 200 ft above ‘minimum pool’ which is usually the level of the original creek bed. Try and find a USGS or COE reading if that lake has one. 

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I can't answer your questions.  But I can tell you what's going on near me.

 

My local lake is one of three reservoirs for the city.  We've been under a drought for several years in a row now, and the water levels all year long have been about 8-10 feet below last year's levels.  Last year, we were still under a drought and the water levels were 2-3 feet below the year before.  However, if they declare that the water levels are low, then they have to impose water rationing, and no one wants that.  So, rather than admit we're in a water crisis, they just adjust what "normal" levels are as the water drains.  So while we sit officially at "normal" water levels, three of the four boat ramps are closed along with all four floating boat docks, because they rest on solid ground.  

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11 minutes ago, Darth-Baiter said:

Lake Sonoma

Unfortunately, USGS doesn't have a monitoring station there.  That's the first place to check for lake levels.  USGS has a reference for it as a 423' elevation.  It doesn't list if that's the full pool elevation (I would assume it is) or another point like the dam or a surrounding parking lot.

https://edits.nationalmap.gov/apps/gaz-domestic/public/summary/234892

 

Using google maps and looking at the dam area, you can clearly see what looks like the normal pool, where vegatation changes from shore based to underwater areas.  Marking a point like that and swapping to terrain view says that the 420' elevation is pretty close to there.  For that reason, I'd call 423' elevation as the normal full pool.

 

You're showing an elevation of 402' above.  If we take that to mean the current, that would suggest about 20' low.  Google satellite from this summer is showing that it was a lot lower than that.  I'd guess it was 35-40' low or so.  The bridge piling on the southern end of the dam by the boat ramp is just about hitting dry land.  Navionics puts it in about 40-45' of water so 35-40' low feels about right in the picture. 

 

If all of that anaylsis is correct, then consider it a win.  You've gained back half of the elevation/water with more winter and spring to still come.  You might get back to full pool for pre-spawn.

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53 minutes ago, casts_by_fly said:

Unfortunately, USGS doesn't have a monitoring station there.  That's the first place to check for lake levels.  USGS has a reference for it as a 423' elevation.  It doesn't list if that's the full pool elevation (I would assume it is) or another point like the dam or a surrounding parking lot.

https://edits.nationalmap.gov/apps/gaz-domestic/public/summary/234892

 

Using google maps and looking at the dam area, you can clearly see what looks like the normal pool, where vegatation changes from shore based to underwater areas.  Marking a point like that and swapping to terrain view says that the 420' elevation is pretty close to there.  For that reason, I'd call 423' elevation as the normal full pool.

 

You're showing an elevation of 402' above.  If we take that to mean the current, that would suggest about 20' low.  Google satellite from this summer is showing that it was a lot lower than that.  I'd guess it was 35-40' low or so.  The bridge piling on the southern end of the dam by the boat ramp is just about hitting dry land.  Navionics puts it in about 40-45' of water so 35-40' low feels about right in the picture. 

 

If all of that anaylsis is correct, then consider it a win.  You've gained back half of the elevation/water with more winter and spring to still come.  You might get back to full pool for pre-spawn.

whoa.  you make a lot of sense.  THANKS

 

next big rain it tomorrow and it goes into a smaller event for the next 4 days.  we might get a lot closer.  thanks CBF.

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3 hours ago, Bankc said:

However, if they declare that the water levels are low, then they have to impose water rationing, and no one wants that.  So, rather than admit we're in a water crisis, they just adjust what "normal" levels are as the water drains.

That makes almost no sense.  So they just change the target all the time to fit their needs.  Its no wonder there's a shortage of water.  God forbid people should take shorter showers or not have lush green lawns in a hot, sweltering climate.

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22 minutes ago, casts_by_fly said:

 

Gifts of local dry creek valley wine are always appreciated.  😉

noted.  :D

8 minutes ago, gimruis said:

That makes almost no sense.  So they just change the target all the time to fit their needs.  Its no wonder there's a shortage of water.  God forbid people should take shorter showers or not have lush green lawns in a hot, sweltering climate.

i  dont think that is the case here.  

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  • Super User

We have summer pool and winter pool. I assume full pool is either summer pool or winter pool depending on what time of year it is. 

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Full means exactly that full or maximum pool level at the spillway. Everything else is nonsense. 

Warm Springs dam (lake Sonoma) is a flood control dame feeding into the Russian River and controlled by cubic feed of water discharge to prevent flooding down stream.

What maybe confusing is acre feet of water discharge vs Spillway elevation. 

I was considering buying property at lake Sonoma until deterring the lake was not a water storage facility but a flood control lake that would be drawn down during the wet winter rainy seasons.

Tom

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Just came across this in a google

suggested article. Should give you a good feel for where the lake is relative to a point in time when you last fished it. I use my pictures from a days fishing to correlate dates and water levels. 
 

 

EB0AEB38-3718-484A-86C7-7D8A7DEED789.png

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On 1/7/2023 at 8:19 PM, slonezp said:

We have summer pool and winter pool. I assume full pool is either summer pool or winter pool depending on what time of year it is. 

We have summer pool...which is the lake normal operating level.

Winter pool...aka permanent pool. This lower level is to hold winter and spring rains.

And we have flood pool. This is an elevation above summer pool in which water goes over the spillway gates.

For example, Percy Priest Lake in Nashville has these elevations:

Winter or permanent pool: 480

Summer pool also called Power drawdown pool: 480-490

Flood control pool 490-504.5

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Many of my local lake are Duke Power lakes.  "They" call 100 feet full pool in all of them.   Full pool is spillway level.  They maintain most of them at 97 feet, or 3 feet below the spillway.   Duke power has 11(?) lakes on the Catawba river so if they pull water from one, it's going into the one below it.   They'll start pulling water in pretty much all of them if a bunch of rain is forecasted.  right now Wateree (the last lake on a Catawba river) is low for construction at the hydro station.   Duke power has a bunch of other lakes too.  They have an app called "Lake View"  where you can see lake levels, flow release times, and other information about landings and such.   

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Thanks everyone. Not gonna pretend I fully understand.  But a lot happened in five days!  But note the “full  pool” is now 451 feet. Maybe the initial 200 was a typo?  Same lake. 

 

 

8C738094-EF89-469F-949F-9A6472A6714D.jpeg

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57 minutes ago, Darth-Baiter said:

Thanks everyone. Not gonna pretend I fully understand.  But a lot happened in five days!  But note the “full  pool” is now 451 feet. Maybe the initial 200 was a typo?  Same lake. 

 

 

8C738094-EF89-469F-949F-9A6472A6714D.jpeg

 

 

Since data sourcing/interpretation is one of my interest areas, and data with respect to fishing even more so, you've piqued my interest on this one.  So without further ado, all the data for lake Sonoma.

 

First, the raw data.  It looks like Sonoma Water in conjunction with the Corps of Engineers manage the water.  Here is the lake data page and then the raw water data linked from that page.  Its not quite USGS level interface, but if you play with the web address you can change it from 1 month to 12 months and see what the last year was.  This is also the page that has the 3-graph panel that I coped above (though I didn't know that when I copied it- it came from a newspaper article).

 

https://www.sonomawater.org/current-water-supply-levels

https://cdec.water.ca.gov/dynamicapp/QueryDaily?s=WRS&d=&span=1month

 

Now how to interpret.  I don't know your lake and local levels over the past couple years to say what is 'normal' water level.  Looking at the historical data from the 3-panel chart from 2013 to now (skipping 17 and 18 for some reason) you can see the clear trend each year- steady (almost perfectly linear in fact) drawdown from around March until the rains fill it in Dec-Feb again.  That's pretty normal for a place that has strong seasonal rain and is used for water supply and/or flood control.  If it is just flood control the lakes will typically hold more water longer in the year and then draw down more rapidly in the fall.  Typically those lakes will have a summer pool and a winter pool that is well defined and controlled by dam releases and rain.  In your case, since there is a constant drawdown due to water consumption, that is the overriding water loss.  I would be surprised if anything is released below the dam that isn't minimum requirement unless it is in flood stage (which it's barely been in 10 years).  I suspect that the lake is designed with the flood/supply level as the target level given the constant consumption.

 

So what is that level?  Well the lake was holding it pretty constantly in the beginning of May 2019 based on the acreage graphs.  Its noted as 245k acre-ft.  If you play with the web address and make it 4 years you find that the start of May is roughly 450' elevation.  That ties up with the 451' from lakelevels.  Even more cool is if you read the instructions on the real time data page, you can get custom graphs.  So here is a graph of a little over 3 years leading up to 2019 showing a pretty normal fill and draw down curve.  Rain gets you to full or over full pool in the spring, it discharges down to full and then annual usage kicks in.  Repeat in January.

 

https://cdec.water.ca.gov/jspplot/jspPlotServlet.jsp?sensor_no=4055&end=01%2F11%2F2023+00%3A00&geom=huge&interval=15&cookies=cdec01

 

image.thumb.png.c55e315ccff886ded2d3e2829a6d4fb8.png

 

Now look at the 4 years preceding today.  If you have only fished the lake for the past 3 years, you've never experienced full pool.  The last time the lake was full was Jan 2019.  At its lowest 3 weeks ago it was 80' below full pool.  Right now you'd need to rewind about 2.5 years to get to the stage its in now.  Did you fish it Sept 2020?  That's about what it looks like now.  With the forecast and current water flows, I think you're going to hit full pool imminently.  You've come up 45' in 16 days on a pretty steady rise.  That's 2.5' per day.  Another 10 days of that and you're full.  

 

image.thumb.png.b2ca74a9db1f2a68d66e44758d465b09.png

 

Above in my first analysis I suggested that 420' was full pool due to the vegetation.  Ordinarily that would work, but its been 2.5 years since its been that height.  That's enough time for shoreline vegetation to grow in.  Heck, you're going to have fresh bushes in places that haven't seen standing water in 3 years.  If that level holds for a little while, might I suggest a video to watch:

 

 

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i think the first time, i looked it was a typo.  full pool at 451 feet just makes sense to me and my feeble mind.  for sure, next time i find myself in the room with a few USACE types and i am gonna tap on their shoulder and ask.  

2 hours ago, casts_by_fly said:

 

 

Since data sourcing/interpretation is one of my interest areas, and data with respect to fishing even more so,

you my friend are a very interesting person to me.  i look at a big pile of data and i could break out in hives.  :D

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3 hours ago, Darth-Baiter said:

i think the first time, i looked it was a typo.  full pool at 451 feet just makes sense to me and my feeble mind.  for sure, next time i find myself in the room with a few USACE types and i am gonna tap on their shoulder and ask.  

you my friend are a very interesting person to me.  i look at a big pile of data and i could break out in hives.  :D

 

I'm an engineer by schooling and have worked in R&D and supply chain where data is kinda important...

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On 1/11/2023 at 11:33 AM, Darth-Baiter said:

i think the first time, i looked it was a typo.  full pool at 451 feet just makes sense to me and my feeble mind.  for sure, next time i find myself in the room with a few USACE types and i am gonna tap on their shoulder and ask.  

you my friend are a very interesting person to me.  i look at a big pile of data and i could break out in hives.  :D

 

 

Looks like you've come up 70' of elevation in the past month and are basically at full pool now (and starting to top out).  Given the time of year you'll probably get some more rain to bring it up more but I think its fair to say that you have a much bigger lake to fish now.  Not sure when you're spawning period is (march/april?) but there is going to be a lot of light vegetation along the shoreline for the fish to tuck into.  Should make for some good fishing.

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