4 ms·

California Reservoir Status as maintained by the Army Corps of Engineers: https://www.spk-wc.usace.army.mil/fcgi-bin/midnight.py?days=0&report=COE https://www.

California Reservoir Status as maintained by the Army Corps of Engineers: https://www.spk-wc.usace.army.mil/fcgi-bin/midnight.py?days=0&report=COE https://www.spk-wc.usace.army.mil/fcgi-bin/midnight.py?days=... 1 acre foot is 43560 feet^3, or 1233 m^3 of water.

runarberg 2y ago
acre foot is one of the funnier American units out there. It is defined as a foot × a chain (66 feet) × a furlong (660 feet). So you get this weird rectangular cuboid with very small height and a very long length. m³ is already a pretty hard to visualize unit (unless you are used to visualize volume) but acre feet is just about impossible.
- cesarb 2y ago
  > m³ is already a pretty hard to visualize unit (unless you are used to visualize volume) I don't think it's that hard; just think of a standard 1000L water tank (which is, in my experience, the most common size).
  - ggm 2y ago
    Plastic Tanks being imported from metric economies for sale in imperial measurement economy? It's 264 US gallons. So presumably sold as a 250 gallon tank with a bit of extra headroom.
- BobbyTables2 2y ago
  That’s hilarious. As I read your first sentence, I thought “if only it used furlongs”…. And it does (;->
- kadoban 2y ago
  As a big proponent of the metric system, acre feet are pretty reasonable. An acre is a decent sized plot of land for a house in the ~dense country, you can easily picture it. Flood that to a foot and you have an acre foot. A single m^3 is fairly easy to visualize, but once you get to higher amounts it's pretty meaningless.
  - runarberg 2y ago
    I think you have to be pretty used to visualize volume before it becomes easy. I think having the unit based on a cube still helps though, especially since you can pick a different sized base cube based on the scale (mm³, cm³, deciliter, liter, m³, km³, etc.), having the base unit be this extremely low, and wide rectangular cuboid only aids in your visualization in a very specific context, namely how how many foots you are flooding your acre sized fields with water.
    - opium_tea 2y ago
      Yeah excellent point. When presenting numbers for reading/interpretation then talking in terms of cubes with a certain side length has to be the easiest to interpret. Its important to be specific about the units and not say "5 metres cubed" because that will just lead to confusion with m^3 (already confusing to be fair!). An alternative is using "known" points of reference like Olympic swimming pools, the Sistine Chapel etc (similar to "an area the size of Belgium"). But that risks getting absurd.
- db48x 2y ago
  No, an acrefoot is defined as a foot × an acre. Acres are a unit of area, and can be any shape. They’re especially useful for lakes because you generally know the area that the lake covers and measuring the depth is really easy. If your lake covers 1234 acres and the water rises by a two and a half feet, then obviously you have gained 1234 × 2.5 = 3085 acrefeet of water. It’s designed to be useful without requiring anyone to do any unit conversions at all.
  - rendaw 2y ago
    Firstly I don't think gp meant it literally, but conversationally as in: the definition decomposes to foot x chain x furlong. Acres can be any shape, but gp is correct that acres were originally defined as chain x furlong (per wikipedia https://en.wikipedia.org/wiki/Furlong https://en.wikipedia.org/wiki/Furlong ). They're also correct that it's a weird combination of disparate sizes which doesn't lend itself to visualization.
    - db48x 2y ago
      On the one hand I would argue that you’re not supposed to visualize your lake as a bunch of rectangles. Visualize your lake as the shape the lake actually is. On the other hand, for many people it’s easier to visualize than you might imagine. As you may know, virtually the entire US was surveyed and divided up into one mile × one mile sections. A square mile is exactly 640 acres. At one time a homesteader could buy that square mile and move west. Over time the minimum size of a homestead was halved and halved again until it was 160 acres, or one quarter of a square mile, around the time of the Civil War. These were often quartered again into 40 acre fields. A farmer and his family could expect to work two or three of those fields every year, rotating which one was fallow if they were smart. They are ¼ of a mile on a side. You can zoom in on almost any random part of the US and find those squares everywhere. Farmland is all gridded with roads along the 1 mile section boundaries, and cities are a jumble. But in between the suburbs are made up of the smaller divisions. It is very common for a 40–acre field to be divided up into 13 lots of ~3 acres each. It is super common to find whole areas of 10–acre lots made by quartering those fields. And it is also not surprising to find a 10–acre lot that has been divided up into 1 acre lots that are all 66ft×660ft. Here, as an example I [zoomed into a randomly–chosen point in the midwest](https://www.google.com/maps/@39.6540747,-86.0094355,1456m/data=!3m1!1e3?entry=ttu&g_ep=EgoyMDI1MDEyOS4xIKXMDSoASAFQAw%3D%3D https://www.google.com/maps/@39.6540747,-86.0094355,1456m/da...). If you measure E McGregor Rd along the northern edge of the map you’ll find that it’s 1 mile long until it hits that jog. You can immediately see that this section was subdivided into four 160–acre farms, and some of those were subdivided into 40–acre fields. Knapp Rd runs north–south and divides the section in half. To the east is an older area of mostly 2, 3, and 5–acre lots. On the western side a developer has bought up 90 acres (two 40–acre fields connected by a 10–acre lot) and turned it into a very modern subdivision of houses each built on (approximately) half–acre lots. For many Americans, visualizing an acre is easy; it’s half the size of the land their house was built on, or their lot plus their neighbor’s lot, or some other similar amount.
- timewizard 2y ago
  > a chain (66 feet) × a furlong (660 feet). That's a furrow width x a furrow length. I imagine our agrarian roots have something to do with this. Then you can easily find tables for expected food production from 1 acre of your crops. > weird rectangular cuboid A good 1:10 crop row. > m³ is already a pretty hard to visualize unit 1000 1L bottles doesn't seem that hard to visualize.
  - pizzafeelsright 2y ago
    Acres is easy enough to visualize. About 90 yards of an American football field. Whatever the perimeter the area is about the same. Square is great in a science book but land and reality is easier with divisions by 2,3,4,6,8 etc
    - runarberg 2y ago
      This is just like the other weird American units, it works much better in the specific case it was designed around, but fail really fast and really bad in other contexts. If you are a farmer with 26 acres of field that need to be irrigated the equivalence of 1 foot of water every 2 weeks throughout the dry season which is expected to last 3 months, it is easy to calculate that you need 26 × 6 acre feet of water for that. But ones you use volume for literally anything else the flaws of the unit become very apparent.
- russdill 2y ago
  An acre is a weird unit, but people in the US have a general sense of how large an acre is
  - deleted 2y ago
    [deleted]
- wiether 2y ago
  > m³ is already a pretty hard to visualize unit (unless you are used to visualize volume) but acre feet is just about impossible. Idk about the US but in Europe 1m³ water tanks[0] are extremely popular as rainwater collectors. Also they are approximately the size of a pallet, another popular item. Whereas acre feet, since I don't know what both units are... But "are meter" wouldn't help either, to be fair. [0]: https://www.multicuves.com/2049-thickbox_default/kit-eco-de-couplage-de-2-cuves-a-eau-1000-l-o-15-mm-tuyau-50-cm.jpg https://www.multicuves.com/2049-thickbox_default/kit-eco-de-...
- kristjansson 2y ago
  It’s a great unit for dealing with lots of water though. Talk x billion gallons vs xxx million gallons and people glaze over. A m3 is too small, but the entire Colorado compact is only like 17 km3. The analogous km2-meter might work, but it’s still huge. The acre-foot is a nice manageable size. Plus if you know you’ve got 160 acres planted, and you need 6 in of water over everything, it’s pretty easy figure the volume to request
dmckeon 2y ago
People in the US who work with large volumes of fresh water use acre-feet and cfs (cubic feet per second) almost exclusively. If an article refers to gallons or comparisons like swimming pools instead, consider it popular journalism rather than engineering. Science can use metric, if preferred.

runarberg 2y ago

acre foot is one of the funnier American units out there. It is defined as a foot × a chain (66 feet) × a furlong (660 feet). So you get this weird rectangular cuboid with very small height and a very long length. m³ is already a pretty hard to visualize unit (unless you are used to visualize volume) but acre feet is just about impossible.

cesarb 2y ago
> m³ is already a pretty hard to visualize unit (unless you are used to visualize volume) I don't think it's that hard; just think of a standard 1000L water tank (which is, in my experience, the most common size).
- ggm 2y ago
  Plastic Tanks being imported from metric economies for sale in imperial measurement economy? It's 264 US gallons. So presumably sold as a 250 gallon tank with a bit of extra headroom.
BobbyTables2 2y ago
That’s hilarious. As I read your first sentence, I thought “if only it used furlongs”…. And it does (;->
kadoban 2y ago
As a big proponent of the metric system, acre feet are pretty reasonable. An acre is a decent sized plot of land for a house in the ~dense country, you can easily picture it. Flood that to a foot and you have an acre foot. A single m^3 is fairly easy to visualize, but once you get to higher amounts it's pretty meaningless.
- runarberg 2y ago
  I think you have to be pretty used to visualize volume before it becomes easy. I think having the unit based on a cube still helps though, especially since you can pick a different sized base cube based on the scale (mm³, cm³, deciliter, liter, m³, km³, etc.), having the base unit be this extremely low, and wide rectangular cuboid only aids in your visualization in a very specific context, namely how how many foots you are flooding your acre sized fields with water.
  - opium_tea 2y ago
    Yeah excellent point. When presenting numbers for reading/interpretation then talking in terms of cubes with a certain side length has to be the easiest to interpret. Its important to be specific about the units and not say "5 metres cubed" because that will just lead to confusion with m^3 (already confusing to be fair!). An alternative is using "known" points of reference like Olympic swimming pools, the Sistine Chapel etc (similar to "an area the size of Belgium"). But that risks getting absurd.
db48x 2y ago
No, an acrefoot is defined as a foot × an acre. Acres are a unit of area, and can be any shape. They’re especially useful for lakes because you generally know the area that the lake covers and measuring the depth is really easy. If your lake covers 1234 acres and the water rises by a two and a half feet, then obviously you have gained 1234 × 2.5 = 3085 acrefeet of water. It’s designed to be useful without requiring anyone to do any unit conversions at all.
- rendaw 2y ago
  Firstly I don't think gp meant it literally, but conversationally as in: the definition decomposes to foot x chain x furlong. Acres can be any shape, but gp is correct that acres were originally defined as chain x furlong (per wikipedia https://en.wikipedia.org/wiki/Furlong https://en.wikipedia.org/wiki/Furlong ). They're also correct that it's a weird combination of disparate sizes which doesn't lend itself to visualization.
  - db48x 2y ago
    On the one hand I would argue that you’re not supposed to visualize your lake as a bunch of rectangles. Visualize your lake as the shape the lake actually is. On the other hand, for many people it’s easier to visualize than you might imagine. As you may know, virtually the entire US was surveyed and divided up into one mile × one mile sections. A square mile is exactly 640 acres. At one time a homesteader could buy that square mile and move west. Over time the minimum size of a homestead was halved and halved again until it was 160 acres, or one quarter of a square mile, around the time of the Civil War. These were often quartered again into 40 acre fields. A farmer and his family could expect to work two or three of those fields every year, rotating which one was fallow if they were smart. They are ¼ of a mile on a side. You can zoom in on almost any random part of the US and find those squares everywhere. Farmland is all gridded with roads along the 1 mile section boundaries, and cities are a jumble. But in between the suburbs are made up of the smaller divisions. It is very common for a 40–acre field to be divided up into 13 lots of ~3 acres each. It is super common to find whole areas of 10–acre lots made by quartering those fields. And it is also not surprising to find a 10–acre lot that has been divided up into 1 acre lots that are all 66ft×660ft. Here, as an example I [zoomed into a randomly–chosen point in the midwest](https://www.google.com/maps/@39.6540747,-86.0094355,1456m/data=!3m1!1e3?entry=ttu&g_ep=EgoyMDI1MDEyOS4xIKXMDSoASAFQAw%3D%3D https://www.google.com/maps/@39.6540747,-86.0094355,1456m/da...). If you measure E McGregor Rd along the northern edge of the map you’ll find that it’s 1 mile long until it hits that jog. You can immediately see that this section was subdivided into four 160–acre farms, and some of those were subdivided into 40–acre fields. Knapp Rd runs north–south and divides the section in half. To the east is an older area of mostly 2, 3, and 5–acre lots. On the western side a developer has bought up 90 acres (two 40–acre fields connected by a 10–acre lot) and turned it into a very modern subdivision of houses each built on (approximately) half–acre lots. For many Americans, visualizing an acre is easy; it’s half the size of the land their house was built on, or their lot plus their neighbor’s lot, or some other similar amount.
timewizard 2y ago
> a chain (66 feet) × a furlong (660 feet). That's a furrow width x a furrow length. I imagine our agrarian roots have something to do with this. Then you can easily find tables for expected food production from 1 acre of your crops. > weird rectangular cuboid A good 1:10 crop row. > m³ is already a pretty hard to visualize unit 1000 1L bottles doesn't seem that hard to visualize.
- pizzafeelsright 2y ago
  Acres is easy enough to visualize. About 90 yards of an American football field. Whatever the perimeter the area is about the same. Square is great in a science book but land and reality is easier with divisions by 2,3,4,6,8 etc
  - runarberg 2y ago
    This is just like the other weird American units, it works much better in the specific case it was designed around, but fail really fast and really bad in other contexts. If you are a farmer with 26 acres of field that need to be irrigated the equivalence of 1 foot of water every 2 weeks throughout the dry season which is expected to last 3 months, it is easy to calculate that you need 26 × 6 acre feet of water for that. But ones you use volume for literally anything else the flaws of the unit become very apparent.
russdill 2y ago
An acre is a weird unit, but people in the US have a general sense of how large an acre is
- deleted 2y ago
  [deleted]
wiether 2y ago
> m³ is already a pretty hard to visualize unit (unless you are used to visualize volume) but acre feet is just about impossible. Idk about the US but in Europe 1m³ water tanks[0] are extremely popular as rainwater collectors. Also they are approximately the size of a pallet, another popular item. Whereas acre feet, since I don't know what both units are... But "are meter" wouldn't help either, to be fair. [0]: https://www.multicuves.com/2049-thickbox_default/kit-eco-de-couplage-de-2-cuves-a-eau-1000-l-o-15-mm-tuyau-50-cm.jpg https://www.multicuves.com/2049-thickbox_default/kit-eco-de-...
kristjansson 2y ago
It’s a great unit for dealing with lots of water though. Talk x billion gallons vs xxx million gallons and people glaze over. A m3 is too small, but the entire Colorado compact is only like 17 km3. The analogous km2-meter might work, but it’s still huge. The acre-foot is a nice manageable size. Plus if you know you’ve got 160 acres planted, and you need 6 in of water over everything, it’s pretty easy figure the volume to request

dmckeon 2y ago

People in the US who work with large volumes of fresh water use acre-feet and cfs (cubic feet per second) almost exclusively. If an article refers to gallons or comparisons like swimming pools instead, consider it popular journalism rather than engineering. Science can use metric, if preferred.