5 ms·

Barrels, gallons, acre-inches, acre-feet. This is why I find the metric system so much preferable: only liters and cubic meters (1000 liters).

ghshephard 12y ago
If you have an acre of farmland, an acre-foot of water is the most relevant way of measuring required water.
- hughdbrown 12y ago
  Maybe American farmers should trade in their acres of farmland for hectares. There could be a government program to exchange one for the other. But really -- read the comments and check out the number of times these units are mentioned and converted: - "200 million acre-feet of precipitation to California in average years" - "No doubt when water hits $100/barrel..." - "1 Barrel = 42 Gallons. It costs $0.75/cubic meter (264 Gallons)" - "There are 326,000 gallons in an acre-foot. So, Most Farms can't pay much more than 2000/326000, = $0.006/Gallon." - "$0.75/cubic meter = .75 / 264 = $0.002/Gallon." - "In 2011, the average californian used about 326 gallons/day of water" If you are going to have a conversation about how urban residents compete with farmers for water, it helps to have a common unit. People don't drink water in acre-feet and farmers don't consume gallons or cubic feet or whatever of water. But if the conversation were in liters or cubic meters, at least you'd have a fighting chance of talking the same units. Take this from the comments: "For example, Crystal Springs, a 70k cubic meter reservoir in San Mateo, is entirely for urban use. There is no agriculture competition for it. Every gallon we conserve there, is another gallon conserved for city use." First, it is not 70 000 cubic meters. It's 70 000 000 cubic meters or 70 000 000 000 liters. [1] What would that look like? Well, we have 7e7 cubic meters to divide up into three dimensions. It would be a lake like 700 meters across by 10 meters deep by 10 000 meters long (10 km). Those Californians who consume 326 gallons (1200 liters) per day? One of them could use that reservoir in about 60 000 000 days. Or if you had a million of them, they'd take two months. Four acre-inches would be like [2] one hectare by 10 cm deep -- 10 000 square meters by 0.1 meters, so 1000 cubic meters or 1 000 000 liters. So you can irrigate 70 000 hectares with that much water at that depth per area of land. I am saying the math is way simpler and you can pretty much do it in your head. And you can visualize it. So: common unit across multiple uses, easily scaled up, easily visualized. [1] https://en.wikipedia.org/wiki/Crystal_Springs_Reservoir https://en.wikipedia.org/wiki/Crystal_Springs_Reservoir [2] Not because an acre is the same size as a hectare but because you'd have proportionately fewer hectares than acres.
  - ghshephard 12y ago
    No argument from me on any of that, totally makes sense. And thanks for the correction of 70,000 m^3 -> 70,000 * 1000 m^3 for Crystal Spring Reservoir. (I'll admit to having to have Soulver up just to have this conversation - Metric system would make it way, way easier.)
    - hughdbrown 12y ago
      So when you hear 70 000 cubic meters, try to visualize it: 1.4m deep by 50m long by 25m (1750 cubic meters) is about an Olympic swimming pool. So we would be talking about a reservoir made up of 40 Olympic swimming pools, and then we'd say, "Hey, that seems pretty small for a reservoir." Maybe when wikipedia says that the reservoir is 57,910 acre-feet you have a sense of what that would look like, but I have absolutely no intuition on that, even though I know that an acre is 43 560 square feet and that there are 640 acres to a square mile. [1] https://en.wikipedia.org/wiki/Crystal_Springs_Reservoir https://en.wikipedia.org/wiki/Crystal_Springs_Reservoir
      - ghshephard 12y ago
        I still prefer Metric, but, I have a very good sense of what an acre, 10 acres, and 640 acres are (I have family that farms, and a "section (640 acres)" is a pretty common unit of measurement. 57,910 acre feet would actually be more "intuitive" to me than 70,000 cubic meters (though much harder for me to do calculations and almost impossible to do unit shifting). 57,910 acre feet is roughly 100' deep of water on a section of land. I can "visualize" what that reservoir would would like. Or, for more practical/relevant to irrigation purposes, it's 100 sections of land, 1' deep. But yes, I'm still going to argue for the metric system. I promise.
refurb 12y ago
Really? I find acre-inches pretty intuitive. Maybe convert to hectare-centimeters?
- tanzam75 12y ago
  That's non-metric thinking. In the metric system, you could simply use the cubic meter. A hectare is 10000 square meters. A centimeter is 0.01 meters. Thus, if 1 centimeter of rain falls on a 1 hectare field, then that's simply 100 cubic meters of water. The nice thing about this is that you can easily compare quantities from different contexts. A cubic meter is a cubic meter, whether the water came from a pipe or from the sky. But what does it mean to have an acre-foot of piped water? Nobody specifies pipe cross-sections in acres. Or a barrel of rain falling on a 1-acre field. How many inches is that equivalent to? It's not just water. Look at HVAC. In the US, natural gas is billed in therms, and electricity is billed in kilowatt-hours. In metric countries, both electricity and natural gas are specified in kilowatt-hours. And why not? Energy is energy. If you have a heat pump with gas backup, then you could use gas and electricity interchangeably to heat your house. If you've got a residential cogen system, like they have in Japan, then you could buy either gas or electricity to run your television.
  - ghshephard 12y ago
    What unit do farmers in europe/civilized world pay for their water in? Is it cubic-meters or cm-hectares?
  - mrbabbage 12y ago
    > It's not just water. Look at HVAC. In the US, natural gas is billed in therms, and electricity is billed in kilowatt-hours. In metric countries, both electricity and natural gas are specified in kilowatt-hours. It's funny you use that example, because kWh are silly, unnecessarily convoluted units themselves :-) the "proper" unit for this dimension is the joule, and 1 kWh = 3.6 MJ (1000 J/s ∙ 1 hr ∙ 3600 s / hr ∙ 1 MJ / 1e6 J). There actually is, however, some value in having different units for methane vs electricity, since you have to run methane through a suboptimal furnace to harness its energy. Granted, modern gas-powered furnaces are usually more than 90% efficient, but there's still some loss. And since each customer has a different furnace with a different eta, it's usually not useful to directly compare natural gas tariffs vs electricity tariffs even if you do have a cogen unit.

ghshephard 12y ago

If you have an acre of farmland, an acre-foot of water is the most relevant way of measuring required water.

hughdbrown 12y ago
Maybe American farmers should trade in their acres of farmland for hectares. There could be a government program to exchange one for the other. But really -- read the comments and check out the number of times these units are mentioned and converted: - "200 million acre-feet of precipitation to California in average years" - "No doubt when water hits $100/barrel..." - "1 Barrel = 42 Gallons. It costs $0.75/cubic meter (264 Gallons)" - "There are 326,000 gallons in an acre-foot. So, Most Farms can't pay much more than 2000/326000, = $0.006/Gallon." - "$0.75/cubic meter = .75 / 264 = $0.002/Gallon." - "In 2011, the average californian used about 326 gallons/day of water" If you are going to have a conversation about how urban residents compete with farmers for water, it helps to have a common unit. People don't drink water in acre-feet and farmers don't consume gallons or cubic feet or whatever of water. But if the conversation were in liters or cubic meters, at least you'd have a fighting chance of talking the same units. Take this from the comments: "For example, Crystal Springs, a 70k cubic meter reservoir in San Mateo, is entirely for urban use. There is no agriculture competition for it. Every gallon we conserve there, is another gallon conserved for city use." First, it is not 70 000 cubic meters. It's 70 000 000 cubic meters or 70 000 000 000 liters. [1] What would that look like? Well, we have 7e7 cubic meters to divide up into three dimensions. It would be a lake like 700 meters across by 10 meters deep by 10 000 meters long (10 km). Those Californians who consume 326 gallons (1200 liters) per day? One of them could use that reservoir in about 60 000 000 days. Or if you had a million of them, they'd take two months. Four acre-inches would be like [2] one hectare by 10 cm deep -- 10 000 square meters by 0.1 meters, so 1000 cubic meters or 1 000 000 liters. So you can irrigate 70 000 hectares with that much water at that depth per area of land. I am saying the math is way simpler and you can pretty much do it in your head. And you can visualize it. So: common unit across multiple uses, easily scaled up, easily visualized. [1] https://en.wikipedia.org/wiki/Crystal_Springs_Reservoir https://en.wikipedia.org/wiki/Crystal_Springs_Reservoir [2] Not because an acre is the same size as a hectare but because you'd have proportionately fewer hectares than acres.
- ghshephard 12y ago
  No argument from me on any of that, totally makes sense. And thanks for the correction of 70,000 m^3 -> 70,000 * 1000 m^3 for Crystal Spring Reservoir. (I'll admit to having to have Soulver up just to have this conversation - Metric system would make it way, way easier.)
  - hughdbrown 12y ago
    So when you hear 70 000 cubic meters, try to visualize it: 1.4m deep by 50m long by 25m (1750 cubic meters) is about an Olympic swimming pool. So we would be talking about a reservoir made up of 40 Olympic swimming pools, and then we'd say, "Hey, that seems pretty small for a reservoir." Maybe when wikipedia says that the reservoir is 57,910 acre-feet you have a sense of what that would look like, but I have absolutely no intuition on that, even though I know that an acre is 43 560 square feet and that there are 640 acres to a square mile. [1] https://en.wikipedia.org/wiki/Crystal_Springs_Reservoir https://en.wikipedia.org/wiki/Crystal_Springs_Reservoir
    - ghshephard 12y ago
      I still prefer Metric, but, I have a very good sense of what an acre, 10 acres, and 640 acres are (I have family that farms, and a "section (640 acres)" is a pretty common unit of measurement. 57,910 acre feet would actually be more "intuitive" to me than 70,000 cubic meters (though much harder for me to do calculations and almost impossible to do unit shifting). 57,910 acre feet is roughly 100' deep of water on a section of land. I can "visualize" what that reservoir would would like. Or, for more practical/relevant to irrigation purposes, it's 100 sections of land, 1' deep. But yes, I'm still going to argue for the metric system. I promise.

refurb 12y ago

Really? I find acre-inches pretty intuitive. Maybe convert to hectare-centimeters?

tanzam75 12y ago
That's non-metric thinking. In the metric system, you could simply use the cubic meter. A hectare is 10000 square meters. A centimeter is 0.01 meters. Thus, if 1 centimeter of rain falls on a 1 hectare field, then that's simply 100 cubic meters of water. The nice thing about this is that you can easily compare quantities from different contexts. A cubic meter is a cubic meter, whether the water came from a pipe or from the sky. But what does it mean to have an acre-foot of piped water? Nobody specifies pipe cross-sections in acres. Or a barrel of rain falling on a 1-acre field. How many inches is that equivalent to? It's not just water. Look at HVAC. In the US, natural gas is billed in therms, and electricity is billed in kilowatt-hours. In metric countries, both electricity and natural gas are specified in kilowatt-hours. And why not? Energy is energy. If you have a heat pump with gas backup, then you could use gas and electricity interchangeably to heat your house. If you've got a residential cogen system, like they have in Japan, then you could buy either gas or electricity to run your television.
- ghshephard 12y ago
  What unit do farmers in europe/civilized world pay for their water in? Is it cubic-meters or cm-hectares?
- mrbabbage 12y ago
  > It's not just water. Look at HVAC. In the US, natural gas is billed in therms, and electricity is billed in kilowatt-hours. In metric countries, both electricity and natural gas are specified in kilowatt-hours. It's funny you use that example, because kWh are silly, unnecessarily convoluted units themselves :-) the "proper" unit for this dimension is the joule, and 1 kWh = 3.6 MJ (1000 J/s ∙ 1 hr ∙ 3600 s / hr ∙ 1 MJ / 1e6 J). There actually is, however, some value in having different units for methane vs electricity, since you have to run methane through a suboptimal furnace to harness its energy. Granted, modern gas-powered furnaces are usually more than 90% efficient, but there's still some loss. And since each customer has a different furnace with a different eta, it's usually not useful to directly compare natural gas tariffs vs electricity tariffs even if you do have a cogen unit.