34 replies to this topic

[Steve Heard]

Why the Heck is Folsom Lake so Low?

March 21, 2017

 

On Facebook, here on MyFolsom.com, and all around town, people frequently remark that after all of the rain and snow we’ve had, Folsom Lake still looks like a puddle, and they wonder why.

They will either blame the Bureau of Land Management, the operators of the dam, saying ‘They’re incompetent!’, ‘They’re using an out-dated manual!’, or ‘It’s the Liberal politicians!’, ‘They want to send the water to LA!’

I’m not cynical enough to believe that it could be any of the above, so I just looked at the numbers.

Are you ready for the REAL reason the lake level is so low?

It’s so the lake won’t overflow and flood the Sacramento valley.

Did you know that that was what the dam was designed for? Flood control? Its primary purpose is not drinking water, boating, fishing or giving us something pretty to look at. It’s to prevent flooding.

Take a look at the chart above. Folsom Lake holds about 977,000 acre feet of water. The light blue shaded is the historical average storage throughout the year.

As you can see, it usually peaks in June, after the snow melt, at about 825,000 acre feet.

Looking at the dark blue line, which looks like a roller coaster or an EKG, and you see that the lake was at 800,000 acre feet in February, over 80% of its total capacity, 4 months before the average peak.

If you add up the massive amounts of water the dam operators have released over the past 3 months, it totals over 1,000,000 acre feet of water. That’s more than the entire capacity of the lake, and we still have over 481,000 acre feet remaining, with more rain, snow and snow melt coming.

In other words, the reason the lake is so low, is because the dam operators are doing their job and preventing massive flooding to the half million plus residents of the valley region.

The new spillway nearing completion should be operational before the year is out, and in the future, the dam operators will be able to hold more water for longer periods, which will be helpful in drier years, but they may never allow it to fill up in February.

So, the next time you hear someone complaining that the incompetent dam operators are wasting water, you can set them straight.

You’re welcome.

 

[camay2327]

Steve, they always say that there is so much water coming down the river into the lake later on.

 

I think they are nuts not to keep the lake at least 7/8th full at least.

[kcrides99]

Steve -

Thanks for dispelling any conspiracy theory's!

Unfortunately for the dam operators they are "damned if they do and damned if they don't". How irate would people be if the dam overtopped and caused flooding downstream or worst yet failed?

I for one appreciate their efforts! I am sure there is some room for improvement, particularly once the new spillway is 100% operational, but in the meantime better safe than sorry!

[tony]

Nice work, Steve. One additional thing to think about.  In a very wet year like this one, Folsom Lake will be at a lower level at this point in the year than in a drier year, because the space required for flood control needs to account for (and has the benefit of) the much larger water content of the snow pack, and the possibility that it might melt quickly in a late, warm storm.

 

Minor correction: it's the Bureau of Reclamation, not Land Management, that operates the dam as part of the Central Valley Project.

[2 Aces]

We've been over this before, but I'll give it another shot. Not many people are disputing the *flood control purpose* of Folsom Lake this time of year. What makes many people angry are the LARGE SUMMERTIME WATER RELEASES long after the flood threat has passed, which then results in a low lake level and a 5 MPH speed limit for boaters as early as July. THAT is what ticks people off, in addition to sending all of that perfectly good, fresh water down into the Delta to be washed out to sea.

[sunnyCA]

Are there any plans to build more water storage facilities? I understand that the lake level/dam are for flood control, but given that drought is a very real possibility again in the future, it would seem prudent to start building more storage facilities. We need to store water from years like this one for future use. 

[nomad]

Are there any plans to build more water storage facilities? I understand that the lake level/dam are for flood control, but given that drought is a very real possibility again in the future, it would seem prudent to start building more storage facilities. We need to store water from years like this one for future use. 

 

MAYBE after Trump demolishes the idiotic EPA we may be able to make some traction to build a new dam somewhere in this state. 

[Steve Heard]

We've been over this before, but I'll give it another shot. Not many people are disputing the *flood control purpose* of Folsom Lake this time of year. What makes many people angry are the LARGE SUMMERTIME WATER RELEASES long after the flood threat has passed, which then results in a low lake level and a 5 MPH speed limit for boaters as early as July. THAT is what ticks people off, in addition to sending all of that perfectly good, fresh water down into the Delta to be washed out to sea.

 

I get that. This reason I wrote this post, however, is because of all of the complaints that the lake is at its current level due to incompetence or politics, and that isn't the case.  Our old buddy EDF reminds us that there were a couple of cases when we had a sudden hot spell that melted a lot of snow, overwhelming the system, and that's what they have to protect against at this time of year.

 

The summer stuff is another story.   

 

Are there any plans to build more water storage facilities? I understand that the lake level/dam are for flood control, but given that drought is a very real possibility again in the future, it would seem prudent to start building more storage facilities. We need to store water from years like this one for future use. 

 

I don't know how close we are to getting anything done, but found this interesting piece: https://watershed.uc...r_20Nov2014.pdf

[Bill Z]

Steve, they always say that there is so much water coming down the river into the lake later on.

 

I think they are nuts not to keep the lake at least 7/8th full at least.

Camay, I'm sorry, but your suggestion is nuts. Look at the graph.  You are proposing they keep it at 87.5% of capacity, leaving only 12.5% available for flood control.  Look at how quickly it doubled from 400,000 to 800,000 due to storms, that's roughly going from 40% to 80% full in a few days.  If they kept it at 7/8ths full, the dam could be overtopped from a real warm storm right now and make the scare at Oroville seem like nothing. If it had been 7/8ths full back when it was at 400,000, it may have been catastrophic when those 400,000 plus came down.

 

Steve, excellent find on the graph.  I remember the high water releases back in 1986, way way higher than the releases this year.  Too bad I can't find a picture showing how high it was at Rainbow bridge, but I remember driving over the bridge back then.

[sunnyCA]

Thank you for the watershed report--that's helpful in understanding the issue.

[Steve Heard]

Hey Bill Z! Nice to hear from you! 

[2 Aces]

Steve, if you're associating with people that don't understand the current flood risk, then you're hanging out with the wrong people, if you catch my drift!

[Steve Heard]

Steve, if you're associating with people that don't understand the current flood risk, then you're hanging out with the wrong people, if you catch my drift!

 

It is amazing the lack of knowledge people have about the lake, what it's there for, how much it holds, how much we use, who operates it, etc.

 

On one page folks were blaming the City Council, the Governor, an outdated manual, outright incompetence.

 

Even after seeing the charts and data on it, I've had people say, 'I'm not buyin' it', or 'Something's up.'  I guess we've grown to distrust government entities to the point that we don't even believe that facts are facts.  

[Sandman]

Yes the logical thing would be to build more damns in this state but nothing really ever follows logic in CA. Dont blame the EPA. Its this state that has determined its own fate. Four decades of no new lakes despite 2x the population. Folsom may have been BUILT as a primary means of flood protection. But if people really believe thats still its sole purpose must still be living in the 70s and not just barely survived 5yr of drought.

[Steve Heard]

Yes the logical thing would be to build more damns in this state but nothing really ever follows logic in CA. Dont blame the EPA. Its this state that has determined its own fate. Four decades of no new lakes despite 2x the population. Folsom may have been BUILT as a primary means of flood protection. But if people really believe thats still its sole purpose must still be living in the 70s and not just barely survived 5yr of drought.

It's not it's sole purpose, but it's primary, and if they weren't managing it the way they are this rainy season, there would be a disaster downstream.