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How many inches of rain would 1.4 million gallons be equal to?

Posted 10 years ago

Hi Everyone. I am not a good at mathematics, and I can not figure out how to ask wolfram alpha the question I need the answer to. I was hoping that someone might be kind enough to help me.

I am trying to determine how much rain on an annual basis this would equal:

1.4 Million gallons of water sprayed 6 days a week for a year. The area it will be sprayed on is 600 acres.

Any help at all is appreciated even if it is just the answer. If you can show me how to ask Wolfram alpha that would be great as well in case I need to change the amount of acres.

Thank you to anyone who can help. I really appreciate it. This is very important to a community who is trying to keep a chicken processing plant out of our neighborhood. The plant will use 1.4 million gallons of wastewater daily. They will be spraying it on 600 acres of land. In our part of the country the average rainfall s 45 inches. What I am trying to figure out is how much additional rainfall this wastewater will equal.


POSTED BY: Johnny Ward
5 Replies

One question: Where you state 'The plant will use 1.4 million gallons of wastewater daily" do you mean that that amount of waste water will be generated from, say, reservoir water? Or that they are actually (re)using waste water e.g. pre-treatment rain runoff. If the latter, then they would not be adding wastewater in terms of volume needing treatment (though there would be an increase in volume going through sewers, ditches, or other runoff capture).

There are of course other issues to consider such as effect on soil, groundwater, etc. Best to bring relevant expertise into the discussion (probably you have done so already).

POSTED BY: Daniel Lichtblau
Posted 10 years ago

Here are some actual figures

1 Acre is 6272600 square inches. 1 gallon (US) is 231 cu inches. In a formula:-


which equals 840840/31363 or 26.8099 inches per annum.

That is for all 600 acres, if the actual acreage is less, multiply that figure 26.8099 by 600/X where X is the lesser acreage. so if the acreage covered was only 480 we would get 840840 * 600 /31363 * 480 = 33.51 inches annually, and to work backwards if 60 inches was the depth it would equate to covering 268 of the 600 acres.


POSTED BY: Paul Cleary
Posted 10 years ago

Hi Bill,

That makes sense to me, although just as gut feeling 26" seems low. The concern I have is that someone has quoted a water depth of 60+ inches per year. He does not specifically state 600 acres though. The land the company has purchased will total 600 acres but apparently not all of it will be spray able. Some of it will be covered in trees. To get an 100% accurate figure I will ned to know the exact acreage I guess.

If you have 2 min to look at a video you can see where he quoted these figures at a county commissioners meeting. We have a city council meeting coming up Monday and want to be 100% sure we have our facts right. If we don't and the chicken company catches us on the math it will make the rest of our claims look wrong as well.

Your equation makes sense to me. All I will need to do is change the acres if I can get a more accurate figure of the sprayable acres.

Just in case you are interested here is the video in question where he states his number:

Thank you very much for your help with this. I really appreciate it.

POSTED BY: Johnny Ward
Posted 10 years ago

I sympathize with your gut feeling that the result just somehow doesn't seem right. Perhaps you could measure the area of the base of a gallon milk jug in square feet, look up how many square feet are in an acre, multiply that by 600, and then determine how many milk jugs would "carpet" that 600 acres. That might let you estimate how high you would have to stack milk jugs to get 1.4 million of them in that area. If no mistakes were made in any of that calculation, always something to be watchful for, then hopefully you will end up with "we would need to stack them two or three high." That might give you the needed gut feeling.

Many, maybe even most, people's gut feelings are often in error, sometimes wildly in error. Brains from a million years ago were never really intended to deal with calculations involving a few dozen digits. It is amazing we can learn to do any of this.

These errors in estimation are common and not easy to recognize when dealing with large quantities or long periods of time, especially when dealing with compound interest and exponential growth.

There are some good books out there that can teach you to estimate these sorts of calculations in your head in a few seconds, you have to learn the methods and practice. I used to be able to do compound interest and mortgage amortization calculations in my head.

But when people's agendas get involved or their vague, unstated, even unrecognized, feelings about "how the world ought to be" that was mostly put in place by the time they were age five then the actual facts and real data often make no difference at all, none, zero, More and more I am tending to believe that for most people and most of the issues that people are fighting about, the numbers, the "facts", don't make any difference and the only reason people are looking for those is so they can claim support for their position and discredit their opponent's position. I'd guess more of the numbers and facts are just made up or taken out of context than any of us realize.

I'm sorry.

POSTED BY: Bill Simpson
Posted 10 years ago

See if you can convince yourself if this is correct.

solve 1.4 million gallons6.52.=x inches*600 acres

Both sides are volumes and the only thing we don't know is the depth x in inches.

POSTED BY: Bill Simpson
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