re: Morganza Spillway may or may not open for a 3rd time -- lack of clear info from ACoE

That graphic confuses me. How does the Arkansas river flow 400,000 cfs, meet up with the White river flowing 220,000 cfs but downstream of the confluence only flows 540,000 cfs?

Where's that extra 80,000 cfs?

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Evaporation.

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80,000 cubic feet of water a SECOND?

ETA: I guess over the length of a river, that's not insane. I was thinking of that 80,000 cubic feet as a literal cube of water and the energy density required to make that a gas and the massive expansion going from liquid to gas wasn't making sense. Spread over 100 miles of river, it isn't outlandish.

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The bigger concern is Old River breaking either at the structure itself or along the levee before or after and carving a new path to the Atchafalaya.

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At least you won't have to worry about wetland loss anymore.

There would be continued land loss in SELA. Not sure what you mean.

Don't put a ton of stock into the forecasts until we see the results of the storm on the plains. Precip forecasts can undersell with the amount of moisture and wind energy being provided by this system.

Flooding on the Missouri River and the upper Mississippi is a huge concern post storm and it all will flow down here. The Ohio River side of this storm doesn't look exceptional rainfall wise at least.



Textbook midlat cyclone. Pueblo CO hit 975 mb this morning, a record low for the location.

Any rain is going to be problematic over the snowpack. Makes for a rapid melt. It does look good over the Ohio Valley as the storm will weaken as it moves that direction. Precip can be tricky with this powerful of a low, but at least the focus is toward the west.

The figures listed on that graphic are the maximum flows the levees are designed to safely handle. The math doesn't always add up because the river gets wider and/or deeper in some areas, so the flow rate decreases.

For instance, the Bonnet Carre opens when the flow reaches 1.25 million cuft/sec because the project design is to keep the flow below 1.25 million cuft/sec around New Orleans. If the flow exceeds that, it doesn't mean the levees would fail, just that the flow is higher than what the USACE is comfortable with. I don't know how much wiggle room they factor into their design, but surely it's at least 10 or 15%.

Maybe I'm misusing flow for velocity, but I believe the Corps calls it flow. Perhaps flow rate.

If X volume of water moves thru river cross section A in 1 second, does the same volume move through a downstream river cross section that is 10% larger than A in 1 second? It seems like the flow (flow rate? Velocity?) would decrease to me. I always thought the increasing channel depth and river width slowed the river as it got closer to the mouth.

I guess I've just tried a common sense approach that just makes me look even dumber than usual. I'm not an engineer and only had one physics class about 40 years ago.