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 Topic:  Flow test?? 

Forums -> Archive -> Flow test?? Page 1 of 1
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daniel-todd
Member
Posted: Mar 30, 2011Post Subject: Flow test??
Any clue as to what is going on with the spilling of Slab Creek Dam? Looks like some kind of flow test. Anyway to contact the Dam people to know the spill a head of time. Also it is peaking while it is still dark... that sucks.
daniel-todd
Member
Posted: Apr 1, 2011Post Subject: Website
I have been looking all over the web to find a way to know what is going on with the flow at Slab Creek Dam. CDEC has river info but not for this section of river. I noticed today could be a great day to raft this section if I did not mind putting or taking out in the dark. Any info is very much appreciated.
chris
Site Admin
Posted: Apr 1, 2011
If I had any hard info about what's going on behind the scenes, I'd share, however this has to be part of the snow-melt cycle. You see only short sharp peaks because White Rock Powerhouse diverts over 3500 cfs off the bottom of the graph; what's left in the river below Slab is only the tiny little peaks. They are in the wee hours of the morning since that's when yesterday's snowmelt is arriving.

The overall snow-pack is over 150% of average right now, and since the weather's finally starting to warm up a bit, we're going to start getting serious snow-melt fairly soon. If fact you can see some already on the graphs of free-flowing rivers like the NF American (Clementine) and NF Yuba (Goodyears). Even dam-controlled rivers like SF Yuba and MF Yuba below Our House are showing blips. Note all are peaking in the morning too.
daniel-todd
Member
Posted: Apr 1, 2011Post Subject: lost in the pipelines
Thanks Chris. This does have something to do with the snow melt cycle however it also has something to do with a timed spilling. Chili Bar has a base flow between 3.5-4K. For the past few days when Slab Creek spills Chili Bar goes below that base. Then when the spill stops and the water running down the river bed hits Chili Bar you can notice a peak about the base flow at Chili Bar. The first day the math added up really well. But now it is starting to not add up as well. This must be due to the snow melt. I am not really sure where that water is coming from being Kyberz is still at a low level. I know there is a good distance between the two gauges and a good number of side creeks coming in. The larger one being the Silver Creek. Plus a couple power houses that could be letting out extra due to snow melt but those peaks would be hard to track since we do not access to that data. Anyway Thanks Again.
Ian Buckley
Member
Posted: Apr 1, 2011
Matt, Chris has pretty much got it nailed...full rated output of White Rock powerhouse is approximately 3500cfs. You see fluctuations in its output very quickly reflected in the Chili bar gauge because it's very close. However Spill over the top of Slab Creek takes some hours to get to Chili Bar.

What you are seeing is the Power house reducing it's generating flow every night as power demand reduces, and as a consequence Slab Creek start to spill over the top. It shows up as a curve because it takes time to fill and drain out the river channel.
You see a peak at Chili bar when they increase power house flows UNTIL the corresponding drop in spill flow in the channel reaches the power house. The opposite happens when they decrease flows, you see a dip in Chili bar flow UNTIL the increased spill in the channel reaches White Rock power house.

Note there is also significant accretion in channel adding to the Chili bar flows, most noticeably from Rock Creek which is why the base flow is more than 3500 average when there is no spill.


chris
Site Admin
Posted: Apr 5, 2011
SMUD via Hilde write: "We’re releasing max flows from Union Valley 24x7 which is creating spills at Junction and Camino.  Spills at Slab depend on snow melt down the south fork of the American.  I expect this scenario to continue through the weekend."

The bottom line is that SMUD aren't causing or influencing the Slab spills, they're happening due to water coming down the SFA above Slab. However, the Kyburz gauge is obviously malfunctioning, so it's hard to predict when those spills might occur.
Forums -> Archive -> Flow test?? Page 1 of 1