Another environmental breakdown

Discussions about serious topics, for serious people
Post Reply
User avatar
Grumble
Light of Blast
Posts: 4746
Joined: Mon Nov 11, 2019 1:03 pm

Another environmental breakdown

Post by Grumble » Tue Jan 10, 2023 3:36 pm

https://www.theguardian.com/environment ... SApp_Other

Salt Lake is on the verge of collapse. God knows if the Utahns will get their act together before it’s too late.

Somewhat predictably though I’ve been distracted by the use of the unit “acre-feet” for water quantity. Is this an acre to a depth of one foot? Kind of an intuitive unit if so, and one I applaud.
where once I used to scintillate
now I sin till ten past three

User avatar
Brightonian
Dorkwood
Posts: 1429
Joined: Mon Nov 11, 2019 3:16 pm
Location: Usually UK, often France and Ireland

Re: Another environmental breakdown

Post by Brightonian » Tue Jan 10, 2023 3:46 pm

Grumble wrote:
Tue Jan 10, 2023 3:36 pm
https://www.theguardian.com/environment ... SApp_Other

Salt Lake is on the verge of collapse. God knows if the Utahns will get their act together before it’s too late.

Somewhat predictably though I’ve been distracted by the use of the unit “acre-feet” for water quantity. Is this an acre to a depth of one foot? Kind of an intuitive unit if so, and one I applaud.
It's apparently "approximately an eight-lane swimming pool".

monkey
After Pie
Posts: 1906
Joined: Wed Nov 13, 2019 5:10 pm

Re: Another environmental breakdown

Post by monkey » Tue Jan 10, 2023 3:59 pm

Brightonian wrote:
Tue Jan 10, 2023 3:46 pm
Grumble wrote:
Tue Jan 10, 2023 3:36 pm
https://www.theguardian.com/environment ... SApp_Other

Salt Lake is on the verge of collapse. God knows if the Utahns will get their act together before it’s too late.

Somewhat predictably though I’ve been distracted by the use of the unit “acre-feet” for water quantity. Is this an acre to a depth of one foot? Kind of an intuitive unit if so, and one I applaud.
It's apparently "approximately an eight-lane swimming pool".
So why don't they just use swimming pools as the unit, like normal journalists?

User avatar
bolo
Dorkwood
Posts: 1016
Joined: Mon Nov 11, 2019 1:17 pm
Location: Washington DC

Re: Another environmental breakdown

Post by bolo » Tue Jan 10, 2023 4:01 pm

Or hectare-decimeters?

User avatar
TimW
Catbabel
Posts: 800
Joined: Mon Nov 11, 2019 4:27 pm

Re: Another environmental breakdown

Post by TimW » Tue Jan 10, 2023 4:29 pm

Only about 0.1 Arals though.

User avatar
basementer
Dorkwood
Posts: 1504
Joined: Mon Nov 11, 2019 1:03 pm
Location: 8024, Aotearoa
Contact:

Re: Another environmental breakdown

Post by basementer » Tue Jan 10, 2023 4:47 pm

Grumble wrote:
Tue Jan 10, 2023 3:36 pm
https://www.theguardian.com/environment ... SApp_Other

Salt Lake is on the verge of collapse. God knows if the Utahns will get their act together before it’s too late.

Somewhat predictably though I’ve been distracted by the use of the unit “acre-feet” for water quantity. Is this an acre to a depth of one foot? Kind of an intuitive unit if so, and one I applaud.
I had the same reaction when I first saw "acre-feet", twenty years ago, when I dropped in at the visitor centre of a hydroelectric station. The display board was obviously quite old: Australia had begun using metric units in the 1970s. A little Dymo label added to it gave the capacity of the reservoir in cubic metres.
Money is just a substitute for luck anyway. - Tom Siddell

IvanV
Stummy Beige
Posts: 2658
Joined: Mon May 17, 2021 11:12 am

Re: Another environmental breakdown

Post by IvanV » Tue Jan 10, 2023 5:05 pm

Grumble wrote:
Tue Jan 10, 2023 3:36 pm
Somewhat predictably though I’ve been distracted by the use of the unit “acre-feet” for water quantity. Is this an acre to a depth of one foot? Kind of an intuitive unit if so, and one I applaud.
Only, at the least, if you think an acre is an intuitive unit, which I don't. I don't find it very easy to imagine a piece of land 1 chain by 1 furlong. Nor is imagining quantities of of acres very easy. The USAnian news reports often say, this wildfire now extends to so many million acres, and I have absolutely no vision of what size of a piece of land that might be. I have to convert it to sq km first. I wonder if other people carry around in their heads what a million acres looks like.

So an acre-foot is the quantity of water produced by a foot of rain upon an acre of land. That's fair enough if you want to work out how deep that water would be if placed on different sized pieces of land also measured in acres, and don't mind depths measured in feet. Otherwise it seems a very awkward unit to measure water in, if you wanted to do anything else with it.

Cubic metres is a good unit to measure water in. I know what it looks like and how much it weighs, and can do computations with it. We can also very quickly realise it is the same as a hectare-cm, in the spirit of acre-feet. That realisation fortunately makes it easy for us to compute that an acre foot is about 12 hectare-cm, since there are about 2.5 acres to the hectare. And so an acre-foot amounts to about 12 cubic metres.

In other news about old-fashioned volumetric news, I'm reading a book at the moment about the Frederick the Great of Prussia, by a US author. Quantities of grain and flour - relevant to provisioning armies - are given in the pre-metric German unit, the Wispel. The author helpfully explains that a Wispel is 24 bushels. Not very helpfully as it turns out, because as you went around pre-metric Germany, the size of the bushel (German: Scheffel) varied considerably (as also did the Wispel). A Prussian bushel was about 54.91 litres, in comparison to the standard Imperial bushel of 8 gallons (36.4 litres), which I guess is what the author probably thought he was talking about when he told us a Wispel was 24 bushels. So the quantities of grain he mentions were probably therefore about 50% more than he thought they were. A Prussian Wispel thus amounts to about 1.318 cubic metres, to convert it to that much more useful unit. Since the author at one point gave us the areas of one piece of land in sq miles and another in sq km in the same sentence, I got the impression he was not up to conversions himself.

User avatar
Sciolus
Dorkwood
Posts: 1313
Joined: Mon Nov 11, 2019 6:42 pm

Re: Another environmental breakdown

Post by Sciolus » Tue Jan 10, 2023 8:50 pm

IvanV wrote:
Tue Jan 10, 2023 5:05 pm
Grumble wrote:
Tue Jan 10, 2023 3:36 pm
Somewhat predictably though I’ve been distracted by the use of the unit “acre-feet” for water quantity. Is this an acre to a depth of one foot? Kind of an intuitive unit if so, and one I applaud.
Only, at the least, if you think an acre is an intuitive unit, which I don't. I don't find it very easy to imagine a piece of land 1 chain by 1 furlong. Nor is imagining quantities of of acres very easy. The USAnian news reports often say, this wildfire now extends to so many million acres, and I have absolutely no vision of what size of a piece of land that might be. I have to convert it to sq km first. I wonder if other people carry around in their heads what a million acres looks like.

So an acre-foot is the quantity of water produced by a foot of rain upon an acre of land. That's fair enough if you want to work out how deep that water would be if placed on different sized pieces of land also measured in acres, and don't mind depths measured in feet. Otherwise it seems a very awkward unit to measure water in, if you wanted to do anything else with it.
That's sensible if you're talking about the volume of water to restore a lake, as here, or the amount of rainfall over what area that would be needed. But any unit that is prefaced by "million" is hopelessly unintuitive. Ideally, you would choose units so that the associated number is in the range "a few", and when talking about areas or volumes that should apply to the linear measure. So in the case of 2.5 million acre feet or (Google tells me) 3e9 m3, you could say it's 1.4 km, cubed. Personally, I would go with 30 km x 30 km x 3 m to visualise it. I can imagine a smallish county submerged to the depth of one storey. Which makes it apparent that it's quite a lot (maybe not for America).
Cubic metres is a good unit to measure water in. I know what it looks like and how much it weighs, and can do computations with it. We can also very quickly realise it is the same as a hectare-cm, in the spirit of acre-feet. That realisation fortunately makes it easy for us to compute that an acre foot is about 12 hectare-cm, since there are about 2.5 acres to the hectare. And so an acre-foot amounts to about 12 cubic metres.
Alas, a cubic metre is 0.1 hectare-mm. Areas are hard: you are confusing 1 ha = (100 m)2 (correct) with 1 ha = 100 m2 (wrong).

(6.2 acre-foot per cubic furlong internet points to anyone who spots the inevitable errors in this post.)

User avatar
Bird on a Fire
Princess POW
Posts: 10137
Joined: Fri Oct 11, 2019 5:05 pm
Location: Portugal

Re: Another environmental breakdown

Post by Bird on a Fire » Tue Jan 10, 2023 8:57 pm

How about that environmental breakdown though, eh?

Ten-a-penny nowadays.
We have the right to a clean, healthy, sustainable environment.

User avatar
Sciolus
Dorkwood
Posts: 1313
Joined: Mon Nov 11, 2019 6:42 pm

Re: Another environmental breakdown

Post by Sciolus » Tue Jan 10, 2023 9:07 pm

Yep. Hardly worth mentioning.

Well, it's hard to think of anything to say about it, other than that it's yet another example of a disaster that has obviously been coming for years but which vested short-term interests have kept on creating because a fast buck now is more important than f.cking up later.

User avatar
Grumble
Light of Blast
Posts: 4746
Joined: Mon Nov 11, 2019 1:03 pm

Re: Another environmental breakdown

Post by Grumble » Tue Jan 10, 2023 9:14 pm

Bird on a Fire wrote:
Tue Jan 10, 2023 8:57 pm
How about that environmental breakdown though, eh?

Ten-a-penny nowadays.
They really f.cking are though. Someone should do something.
where once I used to scintillate
now I sin till ten past three

IvanV
Stummy Beige
Posts: 2658
Joined: Mon May 17, 2021 11:12 am

Re: Another environmental breakdown

Post by IvanV » Wed Jan 11, 2023 9:45 am

Sciolus wrote:
Tue Jan 10, 2023 8:50 pm
Alas, a cubic metre is 0.1 hectare-mm. Areas are hard: you are confusing 1 ha = (100 m)2 (correct) with 1 ha = 100 m2 (wrong).
If you knew me, you would know that I probably wouldn't make the obvious error. I know that 1 ha is 10,000 m2 off the top of my head. I do a lot of mental arithmetic with hectares. My mistake was to temporarily think it would take 100 cm3, rather than 10,000 cm3, to cover a square metre to the depth of a cm.

It's a calculation I have made several times before, and now I am reminded of the right answer, I recognise it.

So an acre foot is about 1200 cubic metres.

I do a lot of these conversions and order of magnitude calculations in my head, the instinct of a practical mathematician. It's humbling reminder of the risk of error to to get one two orders of magnitude out without spotting it.

Post Reply