How much rain in Portland this week? Millions of tanker trucks' worth
We all know the Willamette Valley gets a lot of rain, but have you ever thought of just much water really falls in a big rainstorm?
Local engineer Dale Smith had the burning question pop into his head when he read about a statistic that says our "Pineapple Express" type rain storms transports an amount of water vapor equal to between 7.5 to 15 times the average flow of liquid water out of the Mississippi River.
His quest: How many tanker trucks would it take to haul enough water to cover all of the Willamette Valley area with 1 inch of rain -- roughly the amount of total rain expected in the area through the weekend.
(Start formulating your guesses now)
10,000? A million? A billion?
For his base, he's using the double tankers that you see filling up gas stations -- those carry 8,000 gallons of liquid.
Going with just the Portland metro-area counties of Multnomah, Washington and Clackamas, those total 3,071 square miles, which translates to just over 12.3 trillion square inches. (12.3285 trillion to be fairly exact).
Now that we know how much land we need to cover, we need the water. One U.S. Gallon is 231 cubic inches -- a cubic inch of water on a square inch of land would cover that parcel with 1" of water.
So take 8,000 gallons of water in one truck, multiply by 231 and we find each tanker can carry 1,848,000 cubic inches of water.
Thus, just how many trucks would it take to cover those three counties with 1" of rain?!?!
6.67 million! Add in Clark County for our Vancouver friends and it jumps to 8.1 million.
Think of the amount of tanker trucks we'd need to supply the gas for all our water trucks!
Instead, it's provided for free by Mother Nature.
a trillion billion thimbles full!
rain! what rain? All I see is good ol OREGON SUNSHINE
Eh did you calculate the planes fuel to haul all them dang trucks in to the air to release that much water? Better yet, how many tanker planes would it take to do the same feet lol were talking about the planes that are used for dropping water on to fires.
I think someone has way too much time on their hands!
Hmmm.
Actually, most gasoline tanker trucks(the common truck and trailer combo seen in this area) has a licensed GVWR of 105,500lbs and carries 11,000 gallons or so of fuel. Gasoline weighs about 6lbs/gal, while water is near 8.3lbs/gal - so the 8000 gallons would be legal weight for the truck, but it can certainly hold a lot more.
So actually it would only be around 4.7 million truckloads of water if carried at liquid capacity for a normal gasoline load(11,300gal for what I used to drive - and the actual liquid capacity if you topped it off would be about another thousand gallons).
 @mine9 Legal weight plus laws in the state only allow up to 8,000 gallons. They do not allow more because of the greater potential for spillage.
 @scoreboard Huh? You talking about water now? Spillage has nothing to do with anything. It's simple weight calculations - an 8 axle truck as typically seen for a truck/trailer combo will be overweight with more than about 8100 gallons of water. For gasoline that number is closer to 11,300 gallons, a bit less for diesel because it weighs more. The actual capacity of the tanks on the trucks and trailers is typically around 12,300 for the labeled capacity(varies by how each unit is setup and who built it), with maybe room for another 300-500 gal between all 5 compartments for overage before it hits the overflow shutoff. If you want to carry more, I don't think anyone would complain about carrying more, it's just a matter of overweight permits and more axles on the equipment to keep the weight distribution within limits.
 @scoreboard No such mandate. Now perhaps a tractor/trailer combo will only carry 8,000 gallons for longer hauls - but again, that's a weight issue to stay under 80k gvw for traveling to states that don't allow the higher weights we see in the PNW. OR, WA, and ID all allow 105k for the price of a very cheap weight permit, and virtually all the local fuel trucks(truck/trailer combo, not a tractor - the truck has a tank carrying 5000 or so gallons, the trailer carries the rest, over 6000 gallons) carry over 11,000 gallons. I drove one for 4 years, I know what was in it.
 @mine9 Ok you're the expert. I guess I don't know anything, even though I've been selling this type of equipment for over 20 years.Â
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DEQ/EPA mandates, from what I've read, limit the amount of fuel that can be carried to 8,000 gallons even though the trucks are capable of carrying more. It's an environmental thing.
That's a question I never asked, but the answer is quite interesting.
Funny, I barely noticed.
I have an app for this. . . Its called USELESS KNOWLEDGE. Its certainly not NEWS!
 @Justmark grumpy-pants sourhead
@Justmark you get up on the wrong side of the bed?
" . . . 7.5 to 15 times the average flow of liquid water out of the Mississippi River."
Good thing we've got the Columbia River so close to us, isn't it?!
Good story. Shame about the word missing from the very first sentence. I'll make it easy for you, KATU editors (assuming, I know, I know!):
Here's your missing 'how' . . . --> how <--
Fascinating! Really puts it in perspective.